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1. Instrument specific software requirements Water meters Electricity meters Liquid meters Gas meters Requirement block 11 1 Requirement block I2 1 Heat meters Weighing Instr Requirement block 13 1 Requirement block 15 1 Requirement block 14 1 Requirement block I6 1 Figure 3 2 Overview of requirement sets 11 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 In addition to the structure described the requirements of this guide are differentiated according to risk classes Six risk classes numbered from A to F with increasing risk assumptions are introduced The lowest risk class A and the highest risk class F are not used for the present They are placeholders for the eventual case that they will become necessary in future The remaining risk classes B to E cover all of the instru ment classes falling under the regulation of MID Moreover they provide a sufficient window of opportunity for the case of changing risk evaluations The classes are de fined in Chapter 11 of this guide which is only of an informative character Each measuring instrument must be assigned to a risk class because the particular software requirements to be applied are governed by the risk clas
2. 37 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 Additions for Risk Class E Required Documentation in addition to the documentation required for risk classes B and C Source code that realises the integrity of stored data Validation Guidance in addition to the guidance for risk classes B and C Checks based on the source code e Check whether measures taken for guaranteeing integrity are appropriate and correctly implemented Risk Class B Risk Class C Risk Class D L4 Authenticity of measurement data stored The measurement data stored must be capable of being authentically traced back to the measurement aia Notes The authenticity of measurement data may be needed for reference at a later date e g for checking invoices 2 Authenticity requires the correct assignment linking of measurement data to the measurement that has generated the data 3 Authenticity presupposes an identification of data sets 4 Ensuring authenticity does not necessarily require an encryption of the data Required Documentation Required Documentation in addition to Description of the method used for ensuring the authenticity the documentation required for risk classes B and C The protection measures taken shall be shown Validation Guidance Validation Guidance in addition to the Checks based on documentation guidance for risk classes B and C e Check that there is a correct linkin
3. 5 All programs and program parts involved in the transmission and reception of legally relevant commands or data shall be supervised by the legally relevant software The interface that receives or transmits legally relevant commands or data shall be dedicated to that role and may be used only by legally relevant software Standard interfaces are not excluded however if software protection means are implemented according to extension T Required Documentation The documentation shall include A complete list of all commands together with a declaration of completeness A brief description of their meaning and their effect on the functions and data of the measuring instrument Required Documentation in addition to the documentation required for risk classes B and C The documentation shall show the measures taken to validate the completeness of the documentation of commands The documentation shall contain a protocol that shows the tests of the commands or alternatively any other appropriate measure to prove the correctness Validation Guidance Checks based on documentation Judge whether all documented commands are admissible i e whether they have an allowed impact on the legally relevant software and relevant measurement data or none at all Check whether the manufacturer has given an explicit declaration of completeness of the command documentation Functional checks Carry out practi
4. 1 It shall not be possible to fraudulently simulate spoof approved legally relevant software using simple software tools 2 Presented results can be accepted as authentic if the presentation is issued from within the legally relevant software Specifying Notes 1 Restriction to 1BC 2BC Means are required to protect against intentional misuse including simulation based on additional hardware 3 Presented measurement values shall be accompanied by any information necessary to avoid confusion with other non legally relevant information 4 It shall be ensured by technical means that on the universal computer only the software approved for the legally relevant purpose can perform the legally relevant functions e g a sensor shall only work together with the approved program Required Documentation The documentation should describe how authenticity of the software is guaranteed Required Documentation in addition to the documentation required for risk classes B and C The protection measures taken shall be shown Validation Guidance Checks based on documentation e The examination needs to determine that presentations are generated by legally relevant software and how spoofing by non legally relevant programs may be prevented e Check that the legally relevant tasks can only be performed by the approved legally relevant software Functional checks e Check through visual co
5. WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 Are means employed to ensure the authenticity of the legally relevant software and are the authenticity of the results that are presented guaranteed Is the legally relevant software designed in such a way that other software does not inadmissibly influence it Explanations are needed if there are deviations from software requirements 3 Checklist for specific requirements extension L Checklist for Requirements of Extension L re necessary to reconstruct an earlier measurement EI e E ee changes Are the stored measurement data protected against intentional L3 changes carried out by simple common software tools for risk procedures classes B amp C or by special sophisticated software tools for risk classes D amp E traced back to the measurement that generated them B amp C Are keys treated as legally relevant data and kept secret and a against compromise by simple software tools D amp E Are keys and accompanying data treated as legally relevant data and kept secret and protected against compromise by sophisticated software tools Are Appropriate methods equivalent to electronic payment used Is user able to verify the authenticity of the public key Does the software used for verifying stored measurement data L6 sets display or print the data check the data for changes and warn if a change has occurred Are there means to prevent data detected as having been
6. a built for purpose Measuring instrument an embedded system long term storage of legally relevant data The flow meter DF100 is an independent instrument with a transducer connected The transducer is fixed to the instrument and cannot be disconnected The measured volume is indicated on a display No communication with other devices is possible The embedded software of the measuring instrument was developed by Dynaflow P O Box 1120333 100 Reykjavik Iceland 101 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 The version of the software validated is V1 2c The source code comprises following files main c 12301 byte 23 Nov 2003 int c 6509 byte 23 Nov 2003 filter c 10897 byte 20 Oct 2003 input c 2004 byte 20 Oct 2003 display c 32000 byte 23 Nov 2003 Ethernet c 23455 byte 15 June 2002 driver c 11670 byte 15 June 2002 calculate c 6788 byte 23 Nov 2003 The validation has been supported by following documents from the manufacturer DF 100 User Manual DF 100 Maintenance Manual Software description DF100 internal design document dated 22 Nov 2003 Electronic circuit diagram DF100 drawing no 222 31 date 15 Oct 2003 The final version of the test object was delivered to National Testing amp Measurement Laboratory on 25 November 2003 Examination Procedure The validation has been performed according to the WELMEC 7 2 Software Guide Issue 1 downloaded at www welmec org The valid
7. e g exchangeable storage media portable computer remote computer via arbitrary connections e g direct links networks Software identification A sequence of readable characters of software and that is inextricably linked to the software e g version number checksum Software separation The unambiguous separation of software into legally relevant software and non legally relevant software If no software separation exists the whole software is to consider as legally relevant Sub assembly A hardware device hardware unit that functions independently and makes up a measuring instrument together with other sub assemblies or a measuring instrument with which it is compatible MID Article 4 Transmission of measurement data Transmission of measurement data via communication networks or other means to a distant device where they are further processed and or used for legally regulated purposes Type specific parameter Legally relevant parameter with a value that depends on the type of instrument only Type specific parameters are part of the legally relevant software They are fixed at type approval of the instrument User interface An interface that enables information to be passed between a human user and the measuring instrument or its hardware or software components as e g switch keyboard mouse display monitor printer touchscreen Validation Confirmation by examination and provision of objective evidence i e
8. generated by non legally relevant software and presented e Check whether the realised on display or printout can not be confused with the implementation of mixed indication information originating from legally relevant software is correct Example of an Acceptable Solution e The information to be displayed by the non legally relevant software is transferred via the protective interface see S3 to the legally relevant software Behind the interface it passes through a filter that detects inadmissible information The admissible information is then inserted into the indication controlled by the legally relevant software e On a window style display universal computer the legally relevant software checks in short time intervals whether the window with the legally relevant information is always visible and on top of the window stack If it is hidden minimised or outside the border the software generates a warning or stops the output and processing of measurement values When the measurement is finished the window for legal purposes may be closed Additions for Risk Class E Required Documentation in addition to the documentation required for risk classes B and C Source code of the legally relevant software Validation Guidance in addition to the guidance for risk classes B and C Checks based on the source code e Check that legally relevant software generates the indication of measurement values e Check
9. keeping keys and associated information secret Required Documentation in addition to the documentation required for risk classes B and C The protection measures taken shall shown be Validation Guidance Checks based on documentation e Check that the secret information compromised cannot be Validation Guidance in addition to the guidance for risk classes B and C Checks based on documentation e Check whether the measures taken are appropriate with respect to the required state of the art for a high protection level Example of an Acceptable Solution The secret key and accompanying data are stored in binary format in the executable code of the legally relevant software It is then not obvious at which address these data are stored The system software doesn t offer any features to view or edit these data If the CRC algorithm is used as a signature the initial vector or generator polynomial play the role of a key Example of an Acceptable Solution The secret key is stored in a hardware part that can be physically sealed The software doesn t offer any features to view or edit these data Note A technical solution with a standard personal computer would not be sufficient to ensure high protection level if there were no appropriate hardware protection means for the key and other secret data see basic guide for universal computers U6 1 Public Key Infrastructure The public key
10. securing Required Documentation The documentation should provide assurance that software and stored measurement data cannot be inadmissibly modified Required Documentation in addition to the documentation required for risk classes B and C The protection measures taken shall be shown Validation Guidance Case 1 Closed shell of the software subject to legal control Checks based on documentation e Software modules boot automatically User has no access to the operating system of the PC User has no access to other software than the approved one e A written declaration is given that there are no hidden functions to circumvent the closed shell Case 2 User accessible operating system and or software Checks based on documentation e Checksum over machine code of the software modules is generated Legally relevant software cannot be started if code is falsified Validation Guidance in addition to the guidance for risk classes B and C Checks based on documentation e Check whether the measures taken are appropriate with respect to the required state of the art for a high protection level Example of an Acceptable Solution e Program code and data may be protected by means of checksums The program is calculating its own checksum and compares is with a desired value that is hidden in the executable code If the self check fails the program is blocked e Any signature algorithm sh
11. 5 Measuring Systems for the Continuous and Dynamic Measurement of Quantities of Liquids Other than Water 224004444nnnnsnnnnnnnnnnnnnnnnnnnnnnnnnnnn nn 84 10 6 Weighing Instruments u er2 a 85 OA EE E TEE E E T E EE E ATE 91 10 8 Material Measuresi ne ek ea an 94 10 9 Dimensional Measuring Instruments 0 0 eect eect ee nnnnnnnnennnnnnnnnnnnnnnnnnnnn nn 95 10 10 Exhaust Gas Analysers ipri ee 96 Definition of Risk ClasS 9S nn aisar i 97 Tii General principle scn a een 97 11 2 Description of levels for protection examination and conformity umeeeen 97 11 3 Derivation of risk Classes nn a dee ea garen 98 11 4 Interpretation Of risk classes aan a 98 Pattern for Test Report Including Checklists 4444440400nnnn nenn 100 12 1 Pattern for the general part of the test report 24444444H HR RR nnnnnnnnnnnnnnn 101 12 2 Annex 1 of the test report Checklists to support the selection of the appropriate requirement Sets 224usunnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnn 104 12 3 Annex 2 of the test report Specific checklists for the respective technical PANTS pets ee een 105 12 4 Information to be included in the type approval certificate 44m 108 Cross Reference for MID Software Requirements to MID Articles falalo W219101 0 gt gt J0REREBERSDHESUEAHPEDETSHAERBSESTSEEBSEERRENBSPERHELDNERB RHENEEENEERHERRSPEE PERHEREERRHEREHERENERENER 109
12. Additions for Risk Class E Required Documentation in addition to the documentation required for risk classes B and C Source code of the instrument Validation Guidance in addition to the guidance for risk classes B and C Checks based on the source code e Check the software design whether data flow concerning commands is unambiguously defined in the legally relevant software and can be verified e Search inadmissible data flow from the user interface to domains to be protected e Check with tools or manually that commands are decoded correctly and no undocumented commands exist 18 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 Risk Class B Risk Class C Risk Class D P4 Influence via communication interface Commands inputted via communication interfaces of the instrument shall not inadmissibly influence the Specitying Notes This implies that there is an unambiguous assignment of each command to an initiated function or data change 2 This implies that signals or codes that are not declared and documented as commands have no effect on the instrument s functions and data 3 Commands may be a sequence of electrical optical electromagnetic etc signals on input channels or codes in data transmission protocols 4 The restrictions of this requirement are suspended when a software download according to Extension D is carried out 5 This requirement applies only on interfa
13. Additions for Risk Class E Required Documentation in addition to the documentation required for risk classes B C and D Source code of the fixed software part responsible for collecting the consent of the user owner for a download Validation Guidance in addition to the guidance for risk classes B C and D Checks based on the source code e Check whether measures taken for collecting the consent of the user owner for a download are appropriate 61 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 11 Definition of Risk Classes 11 1 General principle The requirements of this guide are differentiated according to software risk classes Risks are related to software of the measuring instrument and not to any other risks For convenience reasons the shorter term risk class is used Each measuring instrument must be assigned to a risk class because the particular software requirements to be applied are governed by the risk class the instrument belongs to A risk class is defined by the combination of the appropriate levels required for software protection software examination and software conformity Three levels low middle and high are introduced for each of these categories 11 2 Description of levels for protection examination and conformity The following definitions are used for the corresponding levels Software protection levels Low No particular protection measures against intentional chan
14. Technical description of a Type U measuring instrument 34 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 6 2 Specific software requirements for Long term Storage The requirements given in this section are to apply in addition to one set of requirements either for the basic built for purpose instruments or for instruments using universal computer Risk Class B Risk Class C Risk Class D L1 Completeness of measurement data stored The measurement data stored must contain all relevant information necessary to reconstruct an earlier measurement Specifying Notes 1 The stored measurement data may be needed for reference at a later date e g for checking invoices All data necessary for legal and metrological reasons shall be stored together with the measurement value Required Documentation Description of all fields of the data sets Validation Guidance Checks based on documentation e Check whether all information needed for the relevant legal and metrological purposes are contained in the data set Example of an Acceptable Solution A legally and metrologically complete data set comprises the following fields Measurement value s with correct resolution the legally correct unit of measure the unit price or the price to pay if applicable the place and time of the measurement if applicable e identification of the instrument if applicable external storage Data are stored
15. The software implemented in the individual instruments is completely identical to the approved one 11 3 Derivation of risk classes Out of the 27 theoretically possible level permutations only 4 or at the utmost 5 are of practical interest risk classes B C D and E eventually F They cover all of the instrument classes falling under the regulation of MID Moreover they provide a sufficient window of opportunity for the case of changing risk evaluations The classes are defined in the table below Degree of Software Software Risk Class A AN Software Protection Examination Conformity A low low low B middle middle low D high middle middle high high middle F high high high Table 11 1 Definition of risk classes 11 4 Interpretation of risk classes Risk class A It is the lowest risk class at all No particular measures are required against intentional changes of software Examination of software is part of the functional testing of the device Conformity is required on the level of documentation It is not expected that any instrument is classified as a risk class A instrument However by introducing this class the corresponding possibility is held open Risk class B In comparison to risk class A the protection of software is required on the middle level Correspondingly the examination level is up rated to the middle level The conformity remains unchanged in compari
16. and notified bodies which are responsible for conformity assessment of measuring instruments By following the Guide a compliance with the software related requirements contained in the MID can be assumed It can be further assumed that all notified bodies accept this Guide as a compliant interpretation of the MID with respect to software To show how the requirements set up in this Guide are related to the respective requirements in the MID a cross reference has been included in this guide as an annex Chapter 13 The predecessor of this Guide was the Guide 7 1 worked out by WELMEC Working Group 7 Both Guides are based on the same principles and were derived from the requirements of the MID Guide 7 1 has been revised and exists further on Issue 2 but it is now only of informative character whereas the Guide 7 2 is the one that has been recommended by WELMEC for software construction examination and validation of software controlled measuring instruments being subject to the MID Latest information relating to the Guides and the work of WELMEC Working Group 7 is available on the web site http www welmecwg7 ptb de WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 2 Terminology The terminology explained in this section describes the vocabulary as used in this guide References to a standard or to any other source are given if the definition is completely or in essential parts taken from it Acceptable solution A design or a principle o
17. be used The user must be able to verify the authenticity of the public key Required Documentation Description of the key management and means for keeping keys and associated information secret Required Documentation in addition to the documentation required for risk classes B and C The protection measures taken shall shown be Validation Guidance Checks based on documentation e Check that the secret information compromised cannot be Validation Guidance in addition to the guidance for risk classes Band C Checks based on documentation e Check whether the measures taken are appropriate with respect to the required state of the art for a high protection level Example of an Acceptable Solution The secret key and accompanying data are stored in binary format in the executable code of the legally relevant software It is then not obvious at which address these data are stored The system software doesn t offer any features to view or edit these data If the CRC algorithm is used as a signature the initial vector or generator polynomial play the role of a key Example of an Acceptable Solution The secret key is stored in a hardware part that can be physically sealed The software doesn t offer any features to view or edit these data Note A technical solution with a standard personal computer would not be sufficient to ensure high protection level if there were no appropriate
18. classes Validation guidance for Validation guidance for one risk class another risk class Example of an acceptable Example of an acceptable solution for one risk class solution for another risk class Figure 3 3 Structure of a requirement block The requirement block represents the technical content of the requirement including the validation guidance It addresses both the manufacturer and the notified body in two directions 1 to consider the requirement as a minimal condition and 2 not to put demands beyond this requirement Notes for the manufacturer Observe the main statement and the additional specifying notes Provide documentation as required Acceptable solutions are examples that comply with the requirement There is no obligation to follow them The validation guidance has an informative character Notes for notified bodies Observe the main statement and the additional specifying notes Follow the validation guidance Confirm the completeness of the documentation provided 13 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 3 4 How to work with the checklists Checklists are a means of ensuring that all the requirements within a chapter have been covered by the manufacturer or examiner They are part of the pattern test report Be aware the checklists are only of a summarising nature and they do not distinguish between risk classes Checklists do not replace th
19. corrupted data Al 7 1 Suitability Al 8 4 Protection against corruption T7 Transmission delay Al 7 1 Suitability Al 8 4 Protection against corruption T8 Availability of transmission Al 7 1 Suitability services Al 8 4 sernicecs Ad4 7 _________ Protection against corruption 1 Extension S S1 Realisation of software sepa Al 7 6 Suitability ration Al 10 1 Indication of result S2 Mixed indication Al 7 1 Al 7 2 Al 7 6 Suitability Al 10 2 Indication of result S3 Protective software interface Al 7 6 Suitability _ Extension D D1 Download mechanism Al 8 2 Al 8 4 Protection against corruption D2 Authentication of Al 7 6 Suitability downloaded software Al 8 3 Al 8 4 Protection against corruption Al 12 Conformity evaluation D3 Integrity of downloaded soft Al 7 1 Suitability ware Al 8 4 Protection against corruption D4 Traceability of legally rele Al 7 1 Al 7 6 Suitability vant Software Download Al 8 2 Al 8 3 Protection against corruption Al 12 Conformity evaluation D5 Download Consent D5 DownoadCorsentt Al 7 1 Al 7 6_ Suitability Extension Instrument specific Software Requirements 1 1 Al 6 Reliability er Fault Detection MI 001 7 1 MI 002 3 1 nn Bsauremenis tor Luty 4 1 MI 003 4 3 1 MI 004 4 110 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 Requirement MID No Denotation Article Anne
20. data a warning is given if deleting is possible at all Example of an Acceptable Solution e The accidental modification of software and measurement data may be checked by calculating a checksum over the relevant parts comparing it with the nominal value and stopping if anything has been modified e Measurement data are not deleted without prior authorisation e g a dialogue statement or window asking for confirmation of deletion e For fault detection see also Extension Additions for Risk Class E Required Documentation in addition to the documentation required for risk classes B C and D Source code of the instrument Validation Guidance in addition to the guidance for risk classes B C and D Checks based on the source code e Check whether measures taken for detection of changes faults are appropriate e Ifa checksum is realised check whether all parts of the legally relevant software are covered by it 20 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 Risk Class B Risk Class C Risk Class D P6 Protection against intentional changes Legally relevant software shall be secured against the inadmissible modification loading or swapping of epee Notes Instrument without interface Manipulation of program code could be possible by manipulating the physical memory i e the memory is physically removed and substituted by one containing fraudulent software or data To preven
21. in addition to the documentation required for risk classes B and C The measures of ensuring integrity shall be shown by the documentation Validation Guidance in addition to the guidance for risk classes B and C Checks based on documentation e Check whether the measures taken are appropriate with respect to the required state of the art for a high protection level Example of an Acceptable Solution e Generate a hash value of the software to be downloaded algorithms e g SHA 1 RipeMD 160 and encrypt it RSA Elliptic Curves with an appropriate key length e The key for decrypting is stored in the fixed software part Additions for Risk Class E Required Documentation in addition to the documentation required for risk classes B and C Source code of the fixed software part responsible for checking the integrity of the downloaded software Validation Guidance in addition to the guidance for risk classes B and C Checks based on the source code e Check whether measures taken for checking the integrity are appropriate 59 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 Risk Class B Risk Class C Risk Class D D4 Traceability of legally relevant software download It shall 2 guaranteed by appropriate technical means that downloads of legally relevant software are Speiying Notes This requirement enables inspection authorities which are responsible for the metr
22. known to both of the programs that create and verify the checksums 2 Use of means provided by transmission protocols e g TCP IP IFSF Additions for Risk Class E Required Documentation in addition to the documentation required for risk classes B C and D Source code that realises the protection of transmitted data Validation Guidance in addition to the guidance for risk classes B C and D Checks based on the source code e Check whether measures taken for protecting transmitted data are appropriate 45 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 Risk Class B Risk Class C Risk Class D T3 Integrity of data The legally relevant transmitted data must be protected against intentional changes with software tools en Notes This requirement only applies to networks that are open or only partly under legal control not to closed networks 2 The protection must apply against intentional changes carried out by common simple software tools 3 Simple common software tools are understood as tools which are easily available and manageable as e g office packages Specifying Notes 1 This requirement applies to open networks and to closed networks partly under legal control 2 Protection is realised by an electronic signature with an algorithm that guarantees that no identical signature results from different data sets 3 The protection must apply against int
23. of legally relevant parameters can be distinguished type specific parameters and device specific parameters Legally relevant software Programs Data and type specific parameters that belong to the measuring instrument or sub assembly and define or fulfil functions which are subject to legal control Long term storage of measurement data Storage used for keeping measurement data ready after completion of the measurement for later legally relevant purposes e g the conclusion of a commercial transaction Measuring instrument Any device or system with a measurement function The adjective measuring is omitted if confusions can be excluded MID Article 4 Measuring instruments using a universal computer type U Measuring instrument that comprises a general purpose computer usually a PC based system for performing legally relevant functions A type U system is assumed if the conditions of a built for purpose measuring instrument type P are not fulfilled Open network A network of arbitrary participants devices with arbitrary functions The number identity and location of a participant can be dynamic and unknown to the other participants see also Closed network Risk class Class of measurement instrument types with comparable risk assessments Software download The process of automatically transferring software to a target measuring instrument or hardware unit using any technical means from a local or distant source
24. the place of the measurement Required Documentation Document all fields of the data set Validation Guidance Checks based on documentation e Check whether all information for further processing the measurement values at the receiving unit are contained in the data set Example of an Acceptable Solution The data set comprises the following fields e Measurement value s with correct resolution the legally correct unit of measure the unit price or the price to pay if applicable the time and date of the measurement if applicable identification of the instrument if applicable data transmission the place of the measurement if applicable Additions for Risk Class E Required Documentation in addition to the documentation required for risk classes B C and D Source code that generates the data sets for transmission Validation Guidance in addition to the guidance for risk classes B C and D Checks based on the source code e Check whether data sets are built correctly 44 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 Risk Class B Risk Class C Risk Class D T2 Protection against accidental or unintentional changes Specifying Notes 1 Accidental changes of data can be caused by physical effects 2 Unintentional changes are caused by the user of the device 3 Means shall be provided to detect transmission errors Required Documentation Require
25. traceability 60 IL transmission 7 8 10 12 15 19 27 specific requirements 12 34 84 91 42 43 44 45 46 47 49 50 52 94 95 96 106 107 108 104 107 110 111 spoof 32 trust centre 9 39 48 storage type P 7 10 12 15 16 23 34 55 63 84 93 95 96 105 type U 8 12 15 34 84 93 95 96 integrated 7 15 34 37 104 long term 7 8 10 34 42 106 105 sub assembly 8 user interface 8 15 16 18 23 24 subroutine 54 26 34 63 105 109 TAC 17 25 31 32 56 108 validation 13 taximeter 91 water meter 65 test report 100 weighing instrument 41 62 85 117
26. with the same resolution values units etc as indicated or printed on a delivery note Additions for Risk Class E Required Documentation in addition to the documentation required for risk classes B C and D Source code that generates the data sets for storing Validation Guidance in addition to the guidance for risk classes B C and D Checks based on the source code e Check whether the data sets are built correctly 35 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 Risk Class B Risk Class C Risk Class D L2 Protection against accidental or unintentional changes Specifying Notes 1 Accidental changes of data can be caused by physical effects 2 Unintentional changes are caused by the user of the device Data housekeeping duties may require data belonging to paid up or time expired invoices to be deleted from time to time Automatic or semi automatic means should be used to ensure that only specified data is deleted and that the accidental deletion of live data is avoided This is particularly important on networked systems and remote or removable storage where users might not realise the significance of the data 3 A checksum shall be calculated by the receiver and compared with the attached nominal value If the values match the data set is valid and may be used otherwise it must be deleted or marked invalid Required Documentation Required Documentation in Description of
27. 13 1 Given software requirement reference to MID z 4444440nn nennen 109 13 2 Interpretation of MID Articles and Annexes by MID Software Requirements 111 References and Literature 222444440000n4nnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnn 115 NTH EE E EE E E E EEE E E E EE 116 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 Foreword The Guide in hand is based on the Software Requirements and Validation Guide Version 1 00 29 October 2004 developed and delivered by the European Growth Net work MID Software The Network was supported from January 2002 to December 2004 by the EU commission under the contract number G7RT CT 2001 05064 The Guide is purely advisory and does not itself impose any restrictions or additional technical requirements beyond those contained in the MID Alternative approaches may be acceptable but the guidance provided in this document represents the con sidered view of WELMEC as to a good practice to be followed Although the guide is oriented on instruments included in the regulations of the MID the results are of a general nature and may be applied beyond WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 1 Introduction This document provides guidance to all those concerned with the application of the Measuring Instruments Directive MID especially for software equipped measuring instruments It addresses both manufacturers of measuring instruments
28. 2 54 107 dimensional measuring instrument 95 direct trust 39 48 documentation 13 16 24 electrical energy meter 75 76 embedded 7 15 34 63 event logger 7 22 60 exhaust gas analysers 96 fault detection 20 63 111 112 113 114 gas meter 69 111 hash algorithm 9 25 37 46 heat meter 80 identification 8 16 17 22 24 25 32 35 38 40 44 47 52 58 60 105 indication 53 89 110 Software Guide 116 WELMEC 7 2 Issue 1 integrity 7 9 37 38 40 46 47 58 59 109 110 IT configuration 7 10 12 104 key actuation 18 26 56 legal control 8 legally relevant 7 8 16 21 29 51 54 55 64 material measure 94 memory 7 21 22 30 34 63 105 MID 6 8 12 62 network 7 8 16 23 24 34 43 50 107 closed 7 8 23 43 46 47 48 55 63 open 7 8 23 43 46 55 63 notified body NB 13 42 operating system 15 23 24 26 29 30 34 51 63 104 parameter 7 8 22 31 97 109 type specific 8 33 47 27 protective interface 107 110 public key structure 9 risk class 8 9 12 62 64 97 98 secure 7 21 22 30 31 56 58 105 signature algorithm 9 30 37 46 electronic 9 37 46 58 key 9 software download 7 8 10 15 21 27 52 56 60 61 software separation 7 8 10 12 33 51 52 55 110 low level 52 52 53 54 56 61 5 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 sophisticated tools 37 39 46 48 97
29. 8 4 Protection against corruption Note As regards contents paragraph 7 1 of MID Annex is not an issue of Suitability but of Protection against corruption Paragraph 8 109 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 Requirement MID No Denotation Article Annex No Denotation I A AnnkM Annex L4 Authenticity of stored data Al 7 1 Suitability Al 8 4 Protection against corruption Al 10 2 Indication of result L5 Confidentiality of keys Al 7 1 Suitability Al 8 4 Protection against corruption L6 Retrieval of stored data Al 7 2 Suitability Al 10 1 Al 10 2 Al 10 3 Indication of result Al 10 4 L7 Automatic storing Al 7 1 Suitability Al 8 4 Protection against corruption L8 Storage capacity and conti Al 7 1 Suitability nuity Lx All of Extension L Al 11 1 Further processing of data to conclude the trading transaction Extension T T1 Completeness of transmitted Al 7 1 Suitability data Al 8 4 Protection against corruption T2 Protection against accidental Al 7 1 Al 7 2 Suitability changes Al 8 4 Protection against corruption T3 Integrity of data Al 7 1 Suitability Al 8 4 Protection against corruption T4 Authenticity of transmitted Al 7 1 Suitability data Al 8 4 Protection against corruption T5 Confidentiality of keys Al 7 1 Suitability Al 8 4 Protection against corruption T6 Handling of
30. Extension L Long term Storage of Measurement Data 444444444H Henn gt 34 6 1 Technical description u dette eeekel nagudounnth pobre neetenedatcueaueadteawe deen doeaeed 34 6 2 Specific software requirements for Long term Storage uuurnnnnnnnnnnnnnnnnennnn 35 Extension T Transmission of Measurement Data via Communication Networks ssseeseesssesseeeeeseseeseeeeeeeeeeeeeseeesseeseeeeeeseeeeeeees 43 7 1 Techrical deseripl n a 43 7 2 Specific software Requirements for Data Transmission 244sssn nennen 44 Extension S Software Separation nina 51 8 1 Technieal deseripli n rs a enter Hecken 51 8 2 Specific software requirements for software separation uueeennensssennnnennnenennnnnnn 52 Extension D Download of Legally Relevant Software 4440000ssssnns seen 55 9 1 Technical Beseriplion au ss Heel 55 9 2 Specific Software Requirements zuuum44mnsnnnnnnnnnnnnnnnnnnannnnnnnnnnnnnnnnnnnnnnnnnnnn 56 Extension I Instrument Specific Software Requirements sssns4 sn 62 10 1 Water Meters ee ee tas ee er Bee TeRRET 65 10 2 Gas Meters and Volume Conversion Devices 4uuss4244ennennnnnennennnnnnnennnnnnnnen 69 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 11 12 13 14 15 10 3 Active Electrical Energy Meters muusssssssnsannnnnnnnnnnnnnnannnnnnnnnnnnnnnnnnnnnnnnnnnnnn 75 10 4 leat Met rS 4 80 10
31. Physikalisch Technische Bundesanstalt PIB Braunschweig und Berlin Software Leitfaden f r Strahlenschutzdosimeter Beschreibung In Deutschland wird der Software Leitfaden 7 2 der WELMEC f r alle Arten von Messger ten im gesetzlichen Messwesen angewendet Der Software Leitfaden spezifiziert unterschiedliche Risiko Klassen f r unterschiedliche Ger tetypen Strahlenschutzdosimeter geh ren zur Risiko Klasse C In dieser Kopie des Software Leitfadens 7 2 sind die Anforderungen gem Risiko Klasse C gelb markiert Die Softwareanforderungen h ngen von der Gestaltung des Gesamtsystems ab System bedeu tet dabei Anordnung von Detektor en Messsonde n Auswerteger t en Steuereinheit en wie z B PC oder Mikroprozessor mit EPROM die Gestaltung der Software und der Schnittstellen des Systems Auswahl der anzuwendenden Teile des Software Guide Die Abschnitte 1 bis 3 dienen der Einf hrung Hauptanforderungen entweder Abschnitt 4 oder 5 e Das System ist nur f r den Zweck verwendbar f r den es bestimmt ist gt Abschnitt 4 ist g ltig e Das System ist auch f r andere Zwecke verwendbar neben denen f r die es bestimmt ist gt Abschnitt 5 ist g ltig Zusatzanforderungen zus tzlich k nnen ein bis vier weitere Abschnitte gelten e Es werden mit dem System Messwerte gespeichert gt zus tzlich ist Abschnitt 6 g ltig e Es werden innerhalb des Systems Messwerte zwischen unterschiedlichen Komponenten bertra
32. Takes care of housekeeping e g deletes redundant files etc Ensures that any protection removed to facilitate downloading and installation is automatically replaced to the approved level on completion Initiates the appropriate fault handling procedures if a fault occurs mmorpg 56 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 Additions for Risk Class E Required Documentation in addition to the documentation required for risk classes B and C Source code of the fixed software part responsible for the management of the download process Validation Guidance in addition to the guidance for risk classes B and C Checks based on the source code Check whether measures taken for managing the download process are appropriate 57 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 Risk Class B Risk Class C Risk Class D D2 Authentication of downloaded software Means shall be employed to guarantee that the downloaded software is authentic and to indicate that ee Notes Before the downloaded software is used for the first time the measuring instrument shall automatically check that a The software is authentic not a fraudulent simulation b The software is approved for that type of measuring instrument 2 The means by which the software identifies its NB approval status shall be made secure to prevent counterfeiting of the NB status 3 If downloaded software fails any of the abov
33. WG7 Software Guide WELMEC 7 2 Issue 1 3 How to use this guide This section describes the organisation of the guide and explains how to use it 3 1 Overall structure of the guide The guide is organised as a structured set of requirement blocks The overall structure of the guide follows the classification of measuring instruments into basic configurations and the classification of so called IT configurations The set of requirements is complemented by instrument specific requirements Consequently there are three types of requirement sets 1 requirements for two basic configurations of measuring instruments called type P and U 2 requirements for four IT configurations called extensions L T S and D 3 instrument specific requirements called extensions 1 1 1 2 The first type of requirements is applicable to all instruments The second type of re quirements concerns the following IT functions long term storage of measurement data L transmission of measurement data T software download D and software separation S Each set of these requirements is only applicable if the corresponding function exists The last type is a collection of further instrument specific require ments The numbering follows the numbering of instrument specific annexes in the MID The set of requirement blocks that may be applied to a given measuring instru ment is schematically shown in Figure 3 1 Instrument specific the basi
34. a flow concerning commands is unambiguously defined in the legally relevant software and can be verified e Search inadmissible data flow from the user interface to domains to be protected e Check with tools or manually that commands are decoded correctly and no undocumented commands exist 26 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 Risk Class B Risk Class C Risk Class D U4 Influence via communication interface Commands input via non sealed communication interfaces of the device shall not inadmissibly influence the legally relevant software and measurement data Specifying Notes 1 This implies that there is an unambiguous assignment of each command to an initiated function or 2 Those parts of the operating system that interpret Other software parts may use the data change This implies that signals or codes that are not declared and documented as commands have no effect on the instrument s functions and data or codes in data transmission protocols D is carried out legally relevant commands shall be considered to be legally relevant software interface provided they do not disturb or falsify the reception or transmission of legally relevant commands or data Commands may be a sequence of electrical optical electromagnetic etc signals on input channels The restrictions of this requirement are suspended when a software download according to Extension
35. a storage is full or removed disconnected from the instrument a warning shall be given to the operator For further necessary actions refer to the measuring instrument specific requirements Extension 2 The regulation concerning the minimum period for storing measurement data is beyond the scope of this requirement and is left to national regulations It is the responsibility of the owner to have an instrument with sufficient storage capacity to fulfil the requirements applicable to his activity The notified body for EC type examination will check only that the data are stored and retrieved correctly and whether new transactions are inhibited when the storage is full 3 It is also beyond the scope of this requirement to require certain inscriptions on the device as concerning the capacity of the storage the capacity or other accompanying information that allow calculating the capacity However the manufacturer shall make available the information on the capacity Required Documentation Description of management of exceptional cases when storing measurement values Validation Guidance Checks based on documentation e Check that the capacity of storage or a formula for calculating it is given by manufacturer e Check that overwriting of data cannot occur before the end of the data storage period that is foreseen and documented by the manufacturer Functional checks e Check that a warning is issued to the user if he is about
36. ability Changes Al 8 2 Al 8 3 Al 8 4 Protection against corruption P7 Parameter Protection Al 7 1 Suitability Al 8 2 Al 8 3 Al 8 4 Protection against corruption Basic Guide U U1 Manufacturer s Documenta Al 9 3 Information to be borne by and to tion accompany the instrument Al 12 Conformity Evaluation Article 10 Technical Documentation U2 Software Identification Al 7 6 Suitability Al 8 3 Protection against corruption U3 Influence via user interfaces Al 7 1 Suitability U4 Influence via Communication Al 7 1 Suitability Interface Al 8 1 Protection against corruption U5 Protection against accidental Al 7 1 Al 7 2 Suitability or unintentional changes Al 8 4 Protection against corruption U6 Protection against Intentional Al 7 1 Suitability Changes Al 8 2 Al 8 3 Al 8 4 Protection against corruption U7 Parameter Protection Al 7 1 Suitability Al 8 2 Al 8 3 Al 8 4 Protection against corruption U8 Software authenticity and Al 7 1 Al 7 2 Al 7 6 Suitability Presentation of Results Al 8 3 Protection against corruption Al 10 2 Al 10 3 Al 10 4 Indication of result U9 __ Influence of other software Al 7 6 Suitability Extension L L1 Completeness of stored data Al 7 1 Suitability AI 8 4 Protection against corruption AI 10 2 Indication of result L2 Protection against accidental Al 7 1 Al 7 2 Suitability or unintentional changes Al 8 4 Protection against corruption L3 Integrity of data Al 7 1 Suitability Al
37. able as e g office packages ae Notes This requirement applies to all types of storages except integrated storages 2 The protection must apply against intentional changes carried out by special sophisticated soft ware tools 3 Sophisticated software tools are for example de buggers re compilers software development tools etc 4 The protection level shall be equivalent to that re quired for electronic payment 5 Protection is realised by an electronic signature with an algorithm that guarantees that no identical signa ture results from different data sets Note Even if the algorithm and key meet the level high a technical solution with a standard personal computer would not realise this protection level provided that there are no appropriate protection means for the programs that sign or verify a data set see basic guide U for universal computers comment on requirement U6 D Required Documentation The method of how the protection is realised shall be documented Required Documentation in addition to the documentation required for risk classes B and C The protection measures taken shall be shown Validation Guidance Checks based on documentation e If a checksum or signature is used Check that the checksum or signature is generated over the entire data set Check that legally relevant software which reads the data and calculate a checksum or decrypts a signature really comp
38. ainst accidental or unintentional changes Legally relevant software and measurement data shall be protected against accidental or unintentional Specifying Notes 1 Unintentional changes could occur through a Incorrect program design e g incorrect loop operation changing global variables in a function etc b Misuse of the operating system c Accidental overwriting or deletion of stored data and programs refer also to Extension L d Incorrect assignment of measurement transaction data Measurements and data belonging to one measurement transaction must not be mixed with those of a different transaction due to incorrect programming or storage e Physical effects electromagnetic interference temperature vibration etc Required Documentation Required Documentation in The documentation should show the measures that have been addition to the documentation taken to protect the software and data against unintentional required for risk classes B and C changes The documentation shall show the measures taken to validate the effectiveness of the protection means Validation Guidance Validation Guidance in addition e Check that a checksum of the program code and the relevant ang f parameters is generated and checked automatically Checks based on documentation e Check that overwriting of data cannot occur before the end of Check whether the measures the data storage period that is foreseen and documented by t
39. ares calculated and the nominal values e Check that secret data e g key initial value if used are kept secret against spying out with simple tools Functional checks e Check that a falsified data set is rejected by the retrieval program Validation Guidance in addition to the guidance for risk classes B and C Checks based on documentation e Check whether the measures taken are appropriate with respect to the required state of the art for a high protection level Example of an Acceptable Solution Just before the data is reused the value of the checksum is recalculated and compared with the stored nominal value If the values match the data set is valid and may be used otherwise it must be deleted or marked invalid An acceptable solution is the CRC 16 algorithm Note The algorithm is not secret but in contrast to requirement L2 the initial vector of the CRC register or the generator polynomial i e the divisor in the algorithm must be The initial vector and generator polynomial are known only to the programs generating and verifying the checksums They must be treated as keys see L5 Example of an Acceptable Solution Instead of the CRC a signature is calculated A suitable signature algorithm would be one of the hash algorithms e g SHA 1 or RipeMD160 in combination with an encryption algorithm such as RSA or Elliptic Curves The minimum key length is 768 bits RSA or 128 160 bits EC
40. ation Guidance in addition to the guidance for risk classes B and C Checks based on the source code e Check whether measures taken for guaranteeing integrity of transmitted data are appropriate Risk Class B Risk Class C Risk Class D T4 Authenticity of transmitted data Specifying Notes 1a the network address 1b For the receiving program of transmitted relevant data it shall be possible to verify the authenticity and the In a network with unknown participants it is necessary to identify the origin of measurement data transmitted without ambiguity The authenticity relies on the identification number of the data set and In a closed network all participants are known No additional IT means are necessary but the topology of the network the number of participants shall be fixed by sealing 2 Unforeseen delays are possible during transmission For a correct assignment of a received measurement value to a certain measurement the time of measurement must be registered 3 To ensure the authenticity an encryption of measurement data is not necessarily required Required Documentation Network with unknown participants Description of the IT means for correct assigning of measurement value to measurement Closed network Description of the hardware means preserving the number of participants in the network Description of initial identification of the participants Required Documentation in addi
41. ation was performed between 1 November and 23 December 2003 A design review was held on 3 December by Dr K Fehler at Dynaflow head office in Reykjavik Other validation work has been carried out at the National Testing amp Measurement Lab by Dr K Fehler and M S Probl me Following requirements have been validated Specific requirements for embedded software for a built for purpose measuring instrument type P Extension L Long term storage for legally relevant data Checklist for the selection of the configuration is found in annex 1 to this report Risk class C has been applied to this instrument Following validation methods have been applied identification of the software completeness of the documentation examination of the operating manual functional testing software design review review of software documentation data flow analysis simulation of input signals Page 2 3 102 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 Result Following requirements of the WELMEC Software Guide 7 2 have been validated without finding faults P1 P2 P3 P5 P6 P7 Requirement P4 is considered to be non applicable L1 L2 L3 L4 L5 L6 L7 Checklists for the P requirements are found in annex 2 1 of this report Checklists for the L requirements are found in annex 2 2 of this report Two commands which were not initially described in the operator s manual were found The two commands have been included in the oper
42. ator s manual dated 10 December 2003 A software fault which limited the month of February to 28 days also in leap year was found in software package V1 2b This has been corrected in V1 2c The software of the Dynaflow DF100 V1 2c fulfils the essential requirements of the Measuring Instruments Directive The result applies to the tested item only National Testing amp Measurement Lab Software Department Dr K E I N Fehler M S A N S Probl me Technical manager Technical Officer Date 23 December 2003 Page 3 3 103 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 12 2 Annex 1 of the test report Checklists to support the selection of the appropriate requirement Sets The first checklist supports the user to decide which of basic configuration P or U applies for the instrument under test Decision on Instrument Type Is the entire application software constructed for the measuring purpose HY 1 If there is general purpose software is it accessible by or visible to the user N 3 Is the user prevented from accessing the operating system if it is possible to switch to an operating mode not subject to legal control Are the implemented programs and the software environment invariable apart from updates Y eee there any means for programming FE N Tick the empty boxes as appropriate If and only if all answers to the 5 questions can be given as in the P column then
43. c configurations IT configurations that requirements that apply Requirements for one of EN Requirements for those of measuring instruments apply Figure 3 1 Type of requirement sets that should be applied to an instrument The schemes in the following Figure 3 2 show what sets of requirements exist 10 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 Software requirements for basic configurations of measuring instruments Requirements for measuring instruments using universal computers Type U Requirements for built for purpose measuring instruments Type P Requirement block P1 Requirement block U1 Requirement block P2 Requirement block U2 Software requirements for IT configurations Requirements for long term storage of legally relevant data Extension L Requirements for software separation Extension S Requirements for download of legally relevant software Extension D Requirements for transmission of legally relevant data Extension T Requirement block D1 Requirement block S1 Requirement block T1 Requirement block L1 Requirement block D2 Requirement block S2 Requirement block T2 Requirement block L2
44. cal tests spot checks using peripheral equipment if available Validation Guidance in addition to the guidance for risk classes B and C Checks based on documentation Check whether the measures taken and test protocols are appropriate for the high protection level Example of an Acceptable Solution There is a software module that receives and interprets commands from the interface This module belongs to the legally relevant software It only forwards allowed commands to the other legally relevant software modules All unknown or not allowed commands are rejected and have no impact on the legally relevant software or measurement data 27 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 Additions for Risk Class E Required Documentation in addition to the documentation required for risk classes B and C Source code of the instrument Validation Guidance in addition to the guidance for risk classes B and C Checks based on the source code e Check the software design whether data flow concerning commands is unambiguously defined in the legally relevant software and can be verified e Search inadmissible data flow from the interface to domains to be protected e Check with tools or manually that commands are decoded correctly and no undocumented commands exist 28 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 Risk Class B Risk Class C Risk Class D U5 Protection ag
45. ce of other software The legally relevant software shall be designed in such a way that other software does not inadmissibly PONTECESO TAEA TA IONS OO TEPER SANERY SESE ED YY a EN Specifying Notes This requirement implies software separation between the legally relevant and non legally relevant software Extension S shall be observed This is the standard case for universal computers Required Documentation See Extension S Validation Guidance See Extension S Example of an Acceptable Solution See Extension S 33 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 6 Extension L Long term Storage of Measurement Data This is an extension to the specific requirements of embedded software for built for purpose measuring instrument type P requirements and of software for measuring instruments using a universal computer type U requirements It describes the re quirements for the storage of measurement data from when a measurement is physi cally completed to the point in time when all processes to be done by the legally rele vant software are finished It may also be applied to long term storage of the data thereafter 6 1 Technical description The set of requirements of this extension only apply if long term storage of measurement data is included It concerns only those measurement date that are legally relevant Three different technical configurations for long term storage are listed in the following table Fo
46. ces which are not sealed Required Documentation If the instrument has an interface the documentation shall include e A complete list of all commands together with a declaration of completeness e A brief description of their meaning and their effect on the functions and data of the measuring instrument Required Documentation in addition to the documentation required for risk classes B and C e The documentation shall show the measures taken to validate the completeness of the documentation of commands e The documentation shall contain a protocol that shows the tests of the commands or alternatively any other appropriate measure to prove the correctness Validation Guidance Checks based on documentation e Judge whether all documented commands are admissible i e whether they have an allowed impact on the measuring functions and relevant data or none at all e Check whether the manufacturer has given an explicit declaration of completeness of the command documentation Functional checks e Carry out practical equipment if available tests spot checks using peripheral Note If it is not possible to exclude inadmissible effects on the measurement functions or relevant data via the interface and the software cannot be amended accordingly then the test certificate must indicate that the interface is non protective and describe the securing sealing means required This also applies to interface
47. ch His consent is required by default unless he agrees otherwise 3 The readiness of the device for download shall be indicated to the user owner Required Documentation The documentation shall briefly describe the technical means by which the download process accounts for the consent of the user owner Validation Guidance Checks based on documentation e Check by documentation which technical means are implemented to protect from download of legally relevant software without the explicit consent of the user Functional checks e Check that after each download a new consent from the user is required for a new download e Check through spot checks that a software download without user consent is prevented from Example of an Acceptable Solution e A switch or key are acceptable when the user owner is present to initiate download e For remote download the measuring instrument s legally relevant software could contain a secure software switch that the user owner could set to permit remote downloads in his absence e The consent could be limited to one download or a specified number of downloads and there could be a time out after the permission has been given e If digital signatures are used to authenticate the sender the latter s public key should be stored in the fixed software part of the measuring instrument Automatic means would verify the authenticity of the signature attached to the software
48. city rest of items not relevant for software AI 9 2 No specific software relevance Instructions for installation conditions AI 9 3 for compatibility with interface sub P1 U1 assemblies or measuring instruments Beane No specific software relevance Al 9 8 Al 10 Indication of result Al 10 4 Se by means of a display or hard U8 L6 S2 Al 10 2 Significance of result no confusion with U8 L1 L4 L6 additional indications S2 112 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 Software MIE Guide Article i Annex No Denotation Comment en o Al Annex Print or record easily legible and non Al 10 3 Bee U8 L6 S2 For direct sales presentation of the result A to both parties I AI 10 5 For utility meters display for the customer oe 12 6 13 6 Further processing of Al 11 data to conclude the trading transaction Al 11 1 Record of measurement results by a dura _ L8 ble means Al 11 2 Durable proof of the measurement result L1 Le and information to identify a transaction Ready evaluation of the conformity with the P1 P2 U1 U2 Are Conformity evaluation requirements of the Directive D2 D4 Annexes A1 to H1 a No requirements to features of instruments Annex MI 001 MI 001 1 to P MI 001 6 No specific software relevance ee Fault detection eee ee MMU Back up facilities 11 1 to 11 3 ze y Wake up facilities an
49. ck whether all relevant software parts are covered by the algorithm for generating the identification e Check the correct implementation of the algorithm 25 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 Risk Class B Risk Class C Risk Class D U3 Influence via user interfaces Commands entered via the user interface shall not inadmissibly influence legally relevant software and measurement data me Notes This implies that there is an unambiguous assignment of each command to an initiated function or data change 2 This implies that switch or key actuations that are not declared and documented as commands have no effect on the instrument s functions and measurement data 3 Commands may be a single action or a sequence of actions carried out by the operator The user 4 The user shell shall be closed i e the user shall not be able to load programs write programs or perform commands to the operating system Required Documentation The documentation shall include e A complete list of all commands together with a declaration of completeness e A brief description of their meaning and their effect on the functions and data of the measuring instrument Required Documentation in addition to the documentation required for risk classes B and C e The documentation shall show the measures to validate the completeness of the documentation of commands e The documentation shal
50. classes B C and D Checks based on the source code e Check whether measures taken for storing are appropriate and correctly implemented 42 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 7 Extension T Transmission of Measurement Data via Communication Networks This is an extension to the software requirements of the basic guides P and U It must be used only if measurement data are transmitted via communication networks to a distant device where they are further processed and or used for legally regulated purposes This extension does not apply if there is no subsequent legally relevant data processing If software is downloaded to a device subject to legal control the requirements of Extension D apply 7 1 Technical description The set of requirements of this extension applies only if the device under consideration is connected to a network and transmits or receives measurement data that are legally relevant In the following table three network configurations are identified The simplest is an array of devices that are all subject to legal control The participants are fixed at legal verification A variant to this closed network partly under legal control is a net with participants that are not subject to legal control but all are known and do not change during operation An open network has no limitation in identity functionality presence and location of the participants Description of configurations Closed netwo
51. corrupted to be used L7 Are the measurement data stored automatically when the measurement is concluded Does the long term storage have a capacity which is sufficient L8 i for the intended purpose Explanations are needed if there are deviations from software requirements 106 WELMEC WG7 Software Guide 4 Checklist for specific requirements extension T Checklist for Requirements of Extension T Not Applicable Do transmitted data contain all relevant information necessary to present or further process the measurement result in the receiving module Are transmitted data protected against accidental and unintentional changes Are legally relevant transmitted data protected against intentional changes carried out by simple common software tools for risk classes B amp C or by special sophisticated software tools for risk classes D amp E Is it possible for the program that receives transmitted relevant data to verify their authenticity and to assign the measurement values to a particular measurement B amp C Are keys treated as legally relevant data and kept an N and protected against compromise by simple software tools D amp E Are keys and accompanying data treated as legally relevant data and kept secret and protected against compromise by sophisticated software tools Are Appropriate methods equivalent to electronic payment used Is user able to verify the authenticity of the public key Are data that have been d
52. cument represents the considered view of WELMEC as to the best practice to be followed Published by WELMEC Secretariat BEV Arltgasse 35 A 1160 Vienna Austria Tel 43 1 21176 3608 Fax 43 1 49 20 875 E mail welmec metrologie at Website www welmec org WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 10 Software Guide Measuring Instruments Directive 2004 22 EC Contents Foreword eins NEE AR Mica bois hau eal we 5 lntrod ctiO Meesi ieia aa vecihaninedinant uecihami nein wena A AAA LEa 6 HE 16 abl 310 0 9 k Aan einer en E E E A 7 How to use this guide a ae EEE 10 3 1 Overall structure of the Quid sissies icine ee 10 3 2 How to select the appropriate parts of the guide nenennnennnnnnne nenn 12 3 3 How to work with a requirement block ccccceeeeeeeeeeeeeeeeeeeeseeeneeeeeeeeeeeseneneeees 13 3 4 How to work with the checklists mmm 44444444Hnnnnnnnnennnnnnnannnnnnnnnnnnnnnannnen 14 Basic Requirements for Embedded Software in a Built for purpose Measuring Instrument Type P oe ots ini teed a a a E AA 15 4 1 Technical Description seen He 15 4 2 Specific Requirements for Type P 4 unse 16 Basic Requirements for Software of Measuring Instruments using a Universal Computer Type Uj s ssnin ath oh AA AA AN AAA 23 5 1 Technical Descripti M rnia ceed ceded doa aeneo ie 23 5 2 Specific Software Requirements for Type U umssursnssnnnsnnnnnnnnnnnnnnnnnnnnnnnnnn nn 24
53. cumentation domains realise the interface required for risk classes B and e A complete list of all commands together with a declaration of C completeness The realisation of the software e A brief description of their meaning and their effect on the interface shall be shown by the functions and data of the measuring instrument documentation Validation Guidance Validation Guidance in Checks based on documentation addition to the guidance for risk e Check that functions of the legally relevant software that may be classes B and C triggered via the protective software interface are defined and Checks based on described documentation e Check that the parameters that may be exchanged via the Check whether realisation of interface are defined and described the software interface is e Check that the description of the functions and parameters is correct conclusive and complete Example of an Acceptable Solution The data domains of the legally relevant software part are encapsulated by declaring only local variables in the legally relevant part e The interface is realised as a subroutine belonging to the legally relevant software that is called from the non legally relevant software The data to be transferred to the legally relevant software are passed as parameters of the subroutine e The legally relevant software filters out inadmissible interface commands Additions for Risk Class E Required Docume
54. d Documentation in Description of the checksum algorithm if used including the length addition to the documentation of the generator polynomial required for risk classes B and C Description of an alternative method if used The documentation shall show the measures taken to validate the effectiveness of the protection means Validation Guidance Validation Guidance in addition to Checks based on documentation the guidance for risk classes B and C e Check that a checksum over data is generated e Check that legally relevant software that receives the data re Checks based on documentation calculates the checksum and compares it with the nominal value e Check whether the measures contained in the data set taken are appropriate for the high protection level Example of an Acceptable Solution 1 To detect data changes a checksum with the CRC 16 algorithm is calculated over all bytes of a data set and inserted into the data set to be transmitted Just before the data is reused the value of the checksum is recalculated by the receiver and compared with the attached nominal value If the values match the data set is valid and may be used otherwise it must be deleted or marked invalid Note The algorithm is not secret and in contrast to requirement T3 neither is the initial vector of the CRC register nor the generator polynomial i e the devisor in the algorithm The initial vector and generator polynomial are
55. d restoring MI 001 7 1 3 to No specific software relevance MI 001 9 Annex MI 002 MI 002 1 to N MI 002 2 No specific software relevance Electromagnetic immu TAU SEISEION MI 002 3 1 nit Back up facilities 12 1 to 12 3 y Wake up facilities and restoring MI 002 3 1 3 ER to MI 002 5 1 No specific software relevance MI 002 5 2 Suitability Be solution for monitoring battery 12 7 MI 002 5 3 Suitability Internal resolution 12 4 MI 002 5 4 to gt MI 002 8 No specific software relevance MI 002 5 5 Suitability Test element 12 9 MI 002 5 6 to a MI 002 8 No specific software relevance Volume conversion ra MI 002 9 1 devices Acceptable solution for monitoring the gas 12 8 ne volume converter Suitability Mr No specific software relevance MI 002 10 p Annex MI 003 Miosa ta No specific software relevance MI 003 4 2 p Permissible effect of Fault detection MI 003 4 3 transient electromag Back up facilities 13 1 to 13 3 netic phenomena Wake up facilities and restoring 113 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 Annex MI 007 Annex MI 008 Annex MI 009 Annex MI 010 Software MID Guide Article Annex No Denotation Comment nen o Al Annex MI 003 5 1 No specific software relevance MI 003 5 2 Suitability Internal resolution 13 4 MI 003 5 3 to is MI 003 7 No specific software relevance Annex MI 004 MI 004 1 to p MI 004 4 1 No specif
56. documentation shall list the software identifications and describe addition to the documentation how the software identification is created how it is inextricably linked required for risk classes B and C to the software itself how it may be accessed for viewing and how it The documentation shall show the is structured in order to differentiate between version changes with measures taken to protect the and without requiring a type approval software identification from falsification 24 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 Validation Guidance Validation Guidance in addition Checks based on documentation to the documentation required for Examine description of the generation and visualisation of the risk classes B and C software identification Checks based on documentation e Check whether all legally relevant software is clearly identified Check whether the measures and described so that it should be clear to both Notified Body taken to protect from and manufacturer which software functions are covered by the falsification are appropriate software identification and which are not e Check whether a nominal value of the identification version number or functional checksum is supplied by the manufacturer This must be quoted in the test certificate Functional checks e Check whether the software identification can be visualised as described in the documentation e Check whether the present
57. e e g topology block diagram type of computer s type of network etc if not described in the operating manual f The operating manual Risk Class B Risk Class C Risk Class D P2 Software identification The legally relevant software shall be clearly identified An identification of the software shall be inextricably linked to the software itself It shall be presented on command or during operation Specifying Notes Specifying Notes 1 Changes to metrologically relevant 1 In addition to 1B Each change to legally relevant software software require information of the defined as fixed at type approval requires a new software NB The NB decides whether a identification new unique software identification is necessary or not A new software identification is only required if the software changes lead to changes of the approved functions or characteristics 2 The software identification shall have a structure that clearly identifies versions that require type approval and those that do not 3 If functions of the software can be switched by type specific parameters each function or variant may be identified separately or alternatively the complete package may be identified as a whole Required Documentation Required Documentation in The documentation shall list the software identifications and describe addition to the documentation how the software identification is created how it is inextricably lin
58. e corrupted data will not be used according Checks based on documentation to the delivered concept e Check whether the measures taken are appropriate with respect to the required state of the art for a high protection level Example of an Acceptable Solution When the program that is receiving data sets detects a discrepancy between the data set and the nominal value of the signature it first tries to reconstruct the original value if redundant information is available If reconstruction fails it generates a warning to the user does not output the measurement value and e Sets a flag in a special field of the data set status field with the meaning not valid OR e Deletes the corrupted data set Additions for Risk Class E Required Documentation in addition to the documentation required for risk classes B and C Source code of the receiving device Validation Guidance in addition to the guidance for risk classes B and C Checks based on the source code e Check whether measures taken for handling corrupted data are appropriate Risk Class B Risk Class C Risk Class D T7 Transmission delay Specifying Notes The manufacturer shall investigate the timing of the data transmission and shall guarantee that under worst case conditions the measurement is not inadmissibly influenced Required Documentation Description of the concept how measurement is protected against transmissi
59. e requirement definitions Refer to the requirement blocks for complete descriptions Procedure Gather the checklists which are necessary according to the selection described in steps 1 2 and 3 in section 3 2 Go through the checklists and prove whether all requirements have been met Fill in the checklists as required 14 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 4 Basic Requirements for Embedded Software in a Built for purpose Measuring Instrument Type P The set of requirements of this chapter are valid for a built for purpose instrument or for an instrument s component that is of the built for purpose type The validity for sub assemblies is included even if it is not explicitly mentioned in the text If the measuring instrument uses a universal computer general purpose PC the set of requirements in the next chapter must be referred to Type U instrument The requirements of the type U instrument must also be used if the subsequent technical description of built for purpose instruments is not matched 4 1 Technical Description A type P instrument is a measuring instrument with an embedded IT system in general it is a microprocessor or microcontroller based system It is characterised by the following features e The entire application software has been constructed for the measuring purpose This includes both functions subject to legal control and other functions e The software is designed and treat
60. e tests see D1 Required Documentation Required Documentation in addition to The documentation should describe the documentation required for risk e How authenticity of the software identification is classes B and C guaranteed The realisation of authentication shall be e How the authenticity of NB approval is guaranteed shown by the documentation e How it is guaranteed that the downloaded software is approved for the type of measuring instrument to which it has been downloaded Validation Guidance Validation Guidance in addition to the Checks based on documentation and functional checks Quidance for risk classes Band C e Check the documentation how a download of Checks based on documentation fraudulent software is prevented e Check whether the measures taken e Check through functional tests that a download of are appropriate with respect to the fraudulent software is prevented required state of the art for a high Ensure the authentication check of software according to protection level documentation and through functional tests Example of an Acceptable Solution 1 Authenticity For integrity reasons see D3 an electronic signature is generated over the software part to be downloaded Authenticity is guaranteed if a key stored in the fixed software part of the instrument confirms that the signature originates from the manufacturer Key matching shall be done automatically 2 NB The key
61. ed as a whole unless software separation according to Extension S has been observed e The user interface is dedicated to the measuring purpose i e it is normally in an operating mode subject to legal control Switching to an operating mode not subject to legal control is possible e There is no operating system having a user shell that is accessible to the user to load programs send commands to OS e The software and its environment are invariable and there are no means for programming or changing the legally relevant software Software download is only allowed if extension D is observed e Interfaces for transmission of measurement data via open or closed communication networks are allowed Extension T to be observed e The storage of measurement data either on an integrated storage on a remote or on removable storage is allowed Extension L to be observed 15 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 4 2 Specific Requirements for Type P Risk Classes B to E P1 Documentation In addition to the specific documentation required in each of the following requirements the documentation shall basically include a A description of the legally relevant software b A description of the accuracy of the measuring algorithms e g price calculation and rounding algorithms c A description of the user interface menus and dialogues d The unambiguous software identification e An overview of the system hardwar
62. ed identification is correct The documentation plus the executable code if necessary of the pattern is kept at the NB Example of an Acceptable Solution e The identification of legally relevant software comprises two parts Part A hast to be changed if changes to the software require a new approval Part B indicates only minor changes to the software e g bug fixes which need no new approval e Part A of the identification consists Part A of the identification consists of an automatically of a version number or the number generated checksum over the fixed code For other legally of the TAC To prevent it from being relevant software part A is a version number or the changed with simple software tools number of the TAC To prevent it from being changed with it is stored in binary format in the simple software tools it is stored in binary format in the executable program file executable program file e An acceptable solution e Acceptable algorithms for the for performing the checksum are CRC 32 or hash checksum is the CRC algorithms like SHA 1 MD5 16 RipeMD160 etc Additions for Risk Class E Required Documentation in addition to the documentation required for risk classes B and C Source code that contains the generation of the identification Validation Guidance in addition to the guidance for risk classes B and C Checks based on the source code e Che
63. election of instrument specific requirements extension l Select using the respective instrument specific extension l x which if any instrument specific requirements are applicable and apply them accordingly Figure 3 2 Step 4 Selection of the applicable risk class extension l Select the risk class as defined in the respective instrument specific extension I x sub chapter 1 x 6 There the risk class may be defined uniformly for a class of measuring instruments or further differentiated for categories fields of application etc Once the 12 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 applicable risk class has been selected only the respective requirements and validation guidance need to be considered 3 3 How to work with a requirement block Each requirement block contains a well defined requirement It consists of a defining text explanatory specifying notes the documentation to be provided the validation guidance and examples of acceptable solutions if available The content within a re quirement block may be subdivided according to risk classes This leads to the sche matic presentation of a requirement block shown in Figure 3 3 Title of the requirement Main statement of the requirement eventually differentiated between risk classes Specifying notes scope of application additional explanations exceptional cases etc Documentation to be provided eventually differentiated between risk
64. elevant parameter with a value that depends on the individual instrument Device specific parameters comprise calibration parameters e g span adjustment or other adjustments or corrections and configuration parameters e g maximum value minimum value units of measurement etc They are adjustable or selectable only in a special operational mode of the instrument Device specific parameters may be classified as those that should be secured unalterable and those that may be accessed settable parameters by an authorised person e g instrument owner or product vendor Integrated storage non removable storage that is part of the measuring instrument e g RAM EEPROM hard disk Integrity of data and software Assurance that the data and software have not been subjected to any unauthorised changes while in use transfer or storage IT configuration Design of the measuring instrument with respect to IT functions and features that are as regards the requirements independent from the measurement function There are four IT configurations considered in this guide long term storage of measurement data transmission of measurement data software download and software separation see also Basic configuration The terms are accordingly applicable to sub assemblies WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 Legally relevant parameter Parameter of a measuring instrument or a sub assembly subject to legal control The following types
65. ement U6 applies to them 2 Device specific parameters e Secured parameters may be changed using an on board keypad or switches or via interfaces but only before the action of securing Because device specific parameters could be manipulated using simple tools on universal computers they shall not be stored in standard storages of a universal computer Storing of these parameters is acceptable only in additional hardware e Settable device specific parameters may be changed after securing Required Documentation Required Documentation in The documentation shall describe all of the legally relevant Addition to the documentation parameters their ranges and nominal values where they are required for risk classes Band C stored how they may be viewed how they are secured and The protection measures taken for when i e before or after verification parameters shall be shown Validation Guidance Validation Guidance in addition to Checks based on documentation the guidance for risk classes B and e Check that the method for protection of the type specific C parameters is appropriate Checks based on documentation e Check that device specific parameters are not stored on the Check whether the measures standard storages of the universal computer but in separate taken are appropriate with respect hardware that can be sealed and write disabled to the required state of the art for miunchonaicnecks a high protectio
66. entified An identification of the software shall be inextricably linked to the software itself It shall be determined and presented on command or during operation Be Notes ee Notes Identification excludes the Restriction of 1B Low level drivers that are defined as operating system and low level relevant at type approval shall be identified drivers e g video drivers printer 2 Additional to 2B Each change to legally relevant program drivers disk drivers etc but it code defined as fixed at type approval or changes of type does include drivers specially specific parameters require a new software identification programmed for a specific legally relevant task 2 Changes to metrologically relevant software require information of the NB The NB decides whether a new unique software identification is necessary or not A new software identification is only required if the software changes lead to changes of the approved functions or characteristics 3 The software identification shall have a structure that clearly identifies versions that require type approval and those that do not 4 Identifications may be applied to different levels e g to complete programs modules functions etc 5 If functions of the software can be switched by parameters each function or variant may be identified separately or the complete package may be identified as a whole Required Documentation Required Documentation in The
67. entional changes carried out by special sophisticated software tools 4 Sophisticated software tools are e g debuggers re compilers software developing tools etc 5 The protection level shall be equivalent to that required for electronic payment Note Even if the algorithm and key meet the level high a technical solution with a standard personal computer would not realise this protection level provided that there are no appropriate protection means for the programs that sign or verify a data set see basic guide U for universal computers comment on requirement U6 D Required Documentation Description of the protection method Required Documentation in addition to the documentation required for risk classes B and C The protection measures taken shall be shown Validation Guidance Checks based on documentation If a checksum or signature is used Check that the checksum or signature is generated over the entire data set Check that legally relevant software that receives the data re calculates the checksum or decrypts the signature and compares it with the nominal value contained in the data set e Check that secret data e g key initial value if used are kept secret against spying out with simple tools Validation Guidance in addition to the guidance for risk classes Band C Checks based on documentation e Check whether the measures taken are appropriate with respect to the requi
68. er and examiner to prove that they have considered all applicable requirements In addition to the pattern of the test report and the checklists the information required for the type approval certificate are listed in the last subsection of this chapter 100 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 12 1 Pattern for the general part of the test report Test report no XYZ122344 Flow meter Dynaflow model DF101 Validation of Software n annexes Commission The Measuring Instruments Directive MID gives the essential requirements for certain measuring instruments used in the European Union The software of the measuring instrument was validated to show conformance with the essential requirements of the MID The validation was based on the report WELMEC MID Software Requirements Guide WELMEC Guide 7 2 where the essential requirements are interpreted and explained for software This report describes the examination of software needed to state conformance with the MID Client Dynaflow P O Box 1120333 100 Reykjavik Iceland Reference Mr Bjarnur Sigfridson Test Object The Dynaflow flow meter DF100 is a measuring instrument intended to measure flow in liquids The intended range is from 1 l s up to 2000 I s The basic functions of the instrument are measuring of flow in liquids indication of measured volume interface to transducer According to the WELMEC Guide 7 2 the flow meter is described as follows
69. etected as having been corrupted 16 prevented from being used 17 Is it ensured that the measurement is not inadmissibly influenced by a transmission delay T8 Is it ensured that no measurement data get lost if network services become unavailable Explanations are needed if there are deviations from software requirements 5 Checklist for specific requirements extension S Checklist for Requirements of Extension T Requirement procedures Is it ensured that additional information generated by the legally non relevant software part shown on a display or printout cannot be confused with the information that originates from the legally relevant part Is the data exchange between the legally relevant and non legally relevant software performed via a protective software interface that comprises controls the interactions and data flow Explanations are needed if there are deviations from software requirements 2 a is 2 a 2 lt z 107 WELMEC 7 2 Issue 1 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 6 Checklist for specific requirements extension D Checklist for Requirements of Extension T Not Applicable Is downloading and the subsequent installation of software automatic Is it ensured that the software protection environment is at the approved level on completion Are means employed to guarantee that the downloaded software is authentic and to indicate that the downloaded software has been ap
70. eter value The current count can be displayed and can be compared with the initial value of the counter that was registered at the last official verification and is indelibly labelled on the instrument c Changes of parameters are registered in an event logger It is an information record stored in a non volatile memory Each s entry is generated automatically by the legally relevant G software and contains e the identification of the parameter e g the name the parameter value the current or the value before e the time stamp of the change The event logger cannot be deleted or be changed without destroying a seal Risk Class E Required Documentation in addition to the documentation required for risk classes B and C Source code showing the way of securing and viewing legally relevant parameters Validation Guidance in addition to the guidance for risk classes B and C Checks based on the source code e Check in the source code whether measures taken for protecting parameters are appropriate e g adjusting mode disabled after securing 22 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 5 Basic Requirements for Software of Measuring Instruments using a Universal Computer Type U 5 1 Technical Description The set of software requirements in this section apply to a measuring instrument based on a general purpose computer The technical description of the Type U measuring system is summa
71. evant software 4 Non legally relevant software comprises the remaining program units data or parameters not covered above Modifications to this part are allowed without informing the NB provided the subsequent requirements of software separation are observed Required Documentation Required Documentation in Description of all components described in the specifying notes addition to the documentation above that belong to the legally relevant software required for risk classes B and C The correct implementation of software separation shall be shown by the documentation Validation Guidance Validation Guidance in addition to Checks based on documentation the guidance for risk classes B and e Check that all legally relevant components mentioned in C specifying notes 1 through 3 are included in legally relevant Checks based on documentation software e Check whether the realisation of software separation is correct Example of an Acceptable Solution As described by the requirement itself Additions for Risk Class E Required Documentation in addition to the documentation required for risk classes B and C Source code of the legally relevant software Validation Guidance in addition to the guidance for risk classes B and C Checks based on the source code e Check the software design whether data flow concerning legally relevant data is unambiguously defined in the legally rel
72. evant software and can be verified e Check e g by data flow analysis with tools or manually that all program units programs or libraries that are involved in processing the measurement values are registered to the legally relevant software e Search inadmissible data flow from parts not subject to legal control to domains to be protected 52 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 Risk Class B Risk Class C Risk Class D S2 Mixed indication Additional information generated by the software which is not legally relevant may only be shown on a display or printout if it cannot be confused with the information that originates from the legally relevant Specifying Notes As the programmer of the non legally relevant software may not know about the admissibility of indications it is the responsibility of the manufacturer to guarantee that all indicated information fulfil the requirement Required Documentation Required Documentation in addition Description of the software that realises the indication to the documentation required for risk Description how the indication of legally relevant information is classes B and C The realisation of mixed indication shall be shown by the documentation Validation Guidance Validation Guidance in addition to the Functional checks guidance for risk classes B and C e Judge through visual check that additional information Checks based on documentation
73. f a software module or hardware unit or of a feature that is considered to comply with a particular requirement An acceptable solution provides an example of how a particular requirement may be met It does not prejudice any other solution that also meets the requirement Audit trail A software counter e g event counter and or information record e g event logger of the changes to legally relevant software or parameter Authentication Verification of the declared or alleged identity of a user process or device Basic configuration Design of the measuring instrument with respect to the basic architecture There are two different basic configurations built for purpose measuring instruments and measuring instruments using a universal computer The terms are accordingly applicable to sub assemblies Built for purpose measuring instrument type P A measuring instrument designed and built specially for the task in hand Accordingly the entire application software is constructed for the measuring purpose For a more detailed definition refer to Chapter 4 1 Closed network A network of a fixed number of participants with a known identity functionality and location see also Open network Communication interface An electronic optical radio or other technical interface that enables information to be automatically passed between components of measuring instruments or sub assemblies Device specific parameter Legally r
74. f protection is required for risk classes B and guaranteed on completion what happens if a fault occurs C The realisation of the download mechanism shall be shown by the documentation Validation Guidance Validation Guidance in Checks based on documentation addition to the guidance for e Check the documentation how the download procedure is fisk classes Band C managed Checks based on e Check that downloading and installation is handled automatically documentation that the measuring instrument is locked if appropriate and that Check whether the software protection is not compromised following a download realisation of the download e Check that there exists non downloadable fixed legally relevant mechanism is correct software for authenticity and integrity checks e Check that during software download no measurement is possible or correct measurement is guaranteed Functional checks Perform at least one software download to check the correct software download Example of an Acceptable Solution A utility program resident in the fixed part of the software that Handshakes with the sender and checks for consent Automatically inhibits measurement unless correct measurement can be guaranteed Automatically downloads the legally relevant software to a secure holding area Automatically carries out the checks required by D2 to D4 Automatically installs the software into the correct location
75. fic software relevance 111 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 Software ue Guide Article Annex No Denotation Comment nen Al Annex 9 Documentation of design manufacture and operation Enable assessment of confor mity General description of the instrument 10 Technical documenta Description of electronic devices with P1 U1 tion drawings flow diagrams of the logic gen eral software information Location of seals and markings Conditions for compatibility with interfaces and sub assemblies 11 to 27 No specific software relevance Annex Al 1 to Al 5 No specific software relevance 11 1 to 11 3 12 1 to 12 3 Al 6 Reliability Fault detection back up restoring restart 13 1 to 13 3 14 1 to 14 3 16 1 to 16 2 P3 P7 No features to facilitate fraudulent use U3 U8 Al 7 Suitability minimal possibilities for unintentional mis L1 L5 L7 L8 use T1 T8 S2 D3 D4 Al 8 Protection against cor ruption Al 8 1 No influences by the connection of other P4 U4 devices Al 8 2 Securing evidence of intervention at a poner AI 8 3 nn of software evidence of in te 4 UB D2 D4 P5 P7 U5 U7 Al 8 4 Protection of stored or transmitted data L1 L5 T1 T8 D1 D3 AI 8 5 No reset of cumulative registers NE en Information to be borne AI 9 by and to accompany the instrument Measuring capa
76. g between each Checks based on documentation measurement value and the corresponding measurement Check whether the measures taken e If a checksum or signature is used check that the are appropriate with respect to the checksum or signature is generated over the entire data required state of the art for a high set protection level e Check that secret data e g key initial value if used are kept secret against spying out with simple tools Functional checks e Check whether corresponding stored data and data printed on the ticket or invoice are identical Example of an Acceptable Solution A stored data set contains the following data fields additional to the fields defined in L3 e A unique current identification number The identification number is also copied to the delivery note e Time when the measurement has been performed time stamp The time stamp is also copied to the delivery note An identification of the measuring instrument that has generated the value e A signature that is used for ensuring the integrity of data can simultaneously be used for ensuring the authenticity The signature covers all of the fields of the data set Refer to requirement L2 L3 e The ticket may state that the measurement values can be compared with the reference data on a means of storage subject to legal control Assignment is demonstrated by comparing the identification number or time stamp printed on the delivery note wit
77. gen sowohl leitungsgef hrt als auch ohne Leitung gt zus tzlich ist Abschnitt 7 g ltig e Es gibt innerhalb des Systems getrennte Softwareteile f r die Verarbeitung der Messwer te und f r andere Funktionen gt zus tzlich ist Abschnitt 8 g ltig e Es ist vorgesehen dass neue Versionen der Software per Download vom Dosimeteran wender geladen werden k nnen gt zus tzlich ist Abschnitt 9 g ltig Zus tzliche Informationen Abschnitt 10 betrifft andere Messger te als Strahlenschutzdosimeter und wurde daher gel scht Die Abschnitte 11 bis 13 geben weitere Hintergrundinformationen Die Bauart eines Strahlenschutzmessger tes das von diesen Anforderungen abweicht wird zu gelassen wenn die gleiche Messsicherheit auf andere Weise gew hrleistet ist In diesem Fall werden die Anforderungen an die Bauart bei der Zulassung festgelegt 16 Abs 2 der EO European cooperation in legal metrology http www welmec org publications 7 2 asp Ein Beispiel ist ein elektronisches Personendosimter Dies trifft f r alle Dosimetertypen zu die einen PC beinhalten Physikalisch Technische Bundesanstalt PIB Braunschweig und Berlin Software Guide for Radiation Protection Dosemeters Description In Germany the Software Guide 7 2 of the WELMEC is applied for all kinds of measuring in struments in legal metrology The Software Guide specifies different risk classes for different types of instruments Radiation protection
78. ges are required Middle The software is protected against intentional changes made by using easily available and simple common software tools e g text editors High The software is protected against intentional changes made by using sophisticated software tools debuggers and hard disc editors software development tools etc Software examination levels Low Standard type approval functional testing of the instrument is performed No extra software testing is required Middle In addition to the low level the software is examined on the basis of its documentation The documentation includes the description of the software functions parameter description etc Practical tests of the software supported functions spot checks may be carried out to check the plausibility of documentation and the effectiveness of protection measures High In addition to the middle level an in depth test of the software is carried out usually based on the source code Software conformity levels Low The functionality of the software implemented for each individual instrument is in conformity with the documentation approved 97 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 Middle In addition to the conformity level low depending on the technical features parts of the software shall be defined as fixed at type approval i e unalterable without NB approval The fixed part shall be identical in every individual instrument High
79. h that in the stored data set Additions for Risk Class E Required Documentation in addition to the documentation required for risk classes B and C Source code that generates the data sets for storing and realises the authentication Validation Guidance in addition to the guidance for risk classes B and C Checks based on the source code e Check whether the data sets are correctly built and reliably authenticated 38 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 Risk Class B Risk Class C Risk Class D L5 Confidentiality of keys Keys and accompanying data must be treated as legally relevant data and must be kept secret and be Aa Notes This requirement only applies if a secret key is used 3 This requirement applies to measurement data storage which are external from the measuring instrument or realised on universal computers 3 The protection must apply against intentional changes carried out by common simple software tools 4 Ifthe access to the secret keys is prevented e g by sealing the housing of a built for purpose device no additional software protection means are necessary Specifying Notes 1 This requirement applies to storage in universal computers and to external storage 2 The protection must apply against intentional changes carried out by special sophisticated software tools 3 Appropriate methods equivalent to electronic payment shall
80. hardware protection means for the key and other secret data see basic guide for universal computers U6 1 Public Key Infrastructure The public key of the storage subject to legal control has been certified by an accredited Trust Centre Direct Trust It is not necessary to involve a trust centre if by prior agreement both parties are able to read the public key of the measuring instrument directiy at a device subject to legal control that is displaying the relevant data set Additions for Risk Class E Required Documentation in addition to the documentation required for risk classes B and C Source code that realises key management Validation Guidance in addition to the guidance for risk classes B and C Checks based on the source code e Check whether measures taken for key management are appropriate 39 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 Risk Class B Risk Class C Risk Class D L6 Retrieval of stored data The software used for verifying measurement data sets stored shall display or print the data check the data for changes and warn if a change has occurred Data that are detected as having been corrupted must not be used Specifying Notes 1 The measurement data stored might need to be referred to at a later date e g transactions that are queried If there is a doubt on the correctness of a delivery note or ticket it must be possible to identify the measurement da
81. he taken are appropriate for the manufacturer high protection level e Check that a warning is issued to the user if he is about to delete measurement data files Functional checks e Check by practical spot checks that before deleting measurement data a warning is given if deleting is possible at all Example of an Acceptable Solution Prevention from incorrect program design this is beyond the scope of these risk classes e Misuse of the operating system overwriting or deletion of stored data and programs the manufacturer should make full use of the protection or privacy rights provided by the operating system or programming language e The accidental modification of programs amp data files may be checked by calculating a checksum over the relevant code comparing it with the nominal value and stopping if the code has been modified or suitably reacting if parameters or data are concerned e Where the operating system allows it it is recommended that all user rights for the deletion moving or amendment of legally relevant software should be removed and access should be controlled via utility programs Access control to programs and data through the use of passwords is recommended as is the use of read only mechanisms The system supervisor should restore rights only when required Additions for Risk Class E Required Documentation in addition to the documentation required for risk classes B and C Sou
82. ic software relevance Permissible influences Fault detection MI 004 4 2 of electromagnetic dis Back up facilities 14 1 to 14 3 turbances Wake up facilities and restoring MI 004 4 3 to m MI 004 7 No specific software relevance Annex MI 005 Annex MI 006 MI 006 IV Discontinuous and con Fault detection 16 1 to 16 2 MI 006 V tinuous Totalisers Back up facilities 114 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 14 References and Literature 1 Directive 2004 22 EC of the European Parliament and of the Council of 31 March 2004 on measuring instruments Official Journal of the European Union L 135 1 30 4 2004 2 Software Requirements and Validation Guide Version 1 00 29 October 2004 European Growth Network MID Software contract number G7RT CT 2001 05064 2004 3 Software Requirements on the Basis of the Measuring Instruments Directive WEMEC 7 1 Issue 2 2005 115 WELMEC WG7 15 Index audit trail 7 22 31 60 authentication 7 38 47 58 110 authenticity 9 32 33 38 39 40 47 56 58 61 106 107 109 110 basic configuration 7 10 12 104 built for purpose 7 12 15 34 35 51 55 certification of keys 9 checklist 14 104 105 106 107 108 checksum 8 16 17 20 25 29 37 45 circuit 22 command 16 17 18 19 24 25 26 27 41 54 communication interface 19 27 105 confidentiality 39 48 110 cross reference 109 data domain 54 data flow 18 20 26 28 5
83. information that can be proved true based on facts obtained from observations measurement test etc that the particular requirements for the intended use are fulfilled In the present case the related requirements are those of the MID WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 The following definitions are rather specific They are only used in some extensions and for risk classes D or higher Hash algorithm Algorithm that compresses the contents of a data block to a number of defined length hash code so that the change of any bit of the data block leads in practice to another hash code Hash algorithms are selected such that there is theoretically a very low probability of two different data blocks having the same hash code Signature algorithm A cryptographic algorithm that encrypts encodes plaintext to ciphertext Scrambled or secret text using a signature key and that allows decoding of the ciphertext if the corresponding decryption signature key is available Signature key Any number or sequence of characters used encode and decode information There are two different classes of signature keys symmetric key systems and asymmetric key systems Symmetric key means the sender and receiver of information use the same key The key system is called asymmetric if the keys for sender and receiver are different but compatible Usually the key of the sender is known to the sender and the key of the receiver is public in defined envi
84. instruments are of risk class C In this copy of the Software Guide 7 2 the requirements according to risk class C are marked in yellow The software requirements depend on the design of the complete system System means here Arrangement of detector s measuring probe s evaluation device s control unit s as for ex ample PC or microprocessor with EPROM the configuration of the software and of the inter faces of the systems Selection of parts of the Software Guide to be applied Sections 1 to 3 are introductory Principal requirements section 4 or 5 e The system is suitable only for the purpose for which it is intended gt section 4 is valid e The system is suitable also for other purposes in addition to the purposes for which it is intended gt section 5 is valid Additional requirements one to four additional sections may also be valid e The system is used for the storage of measurement values gt section 6 is valid in addition e Inside the system measurement values are transmitted between different components both wire borne and without wire gt section 7 is valid in addition e There are separate software parts inside the system for processing of the measurement values and for other functions gt section 8 is valid in addition e Itis planned that new versions of the software can be loaded by the dosemeter user per download gt section 9 is valid in addition Additional information Sect
85. ion 10 relates to other measuring instruments than radiation protection dosemeters and was therefore deleted Sections 11 to 13 provide additional background information The type of a radiation protection measuring instrument which deviates from these requirements is approved if the same measurement reliability is guaranteed in another way In this case the requirements for the type will be fixed upon approval 16 sec 2 of the Verification Ordinance European cooperation in legal metrology http www welmec org publications 7 2 asp 5 An example is an electronic personal dosemeter This applied to all dosemeter types which comprise a PC WELMEC European cooperation in legal metrology Software Guide Measuring Instruments Directive 2004 22 EC May 2005 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 WELMEC European cooperation in legal metrology WELMEC is a cooperation between the legal metrology authorities of the Member States of the European Union and EFTA This document is one of a number of Guides published by WELMEC to provide guidance to manufacturers of measuring instruments and to Notified Bodies responsible for conformity assessment of their products The Guides are purely advisory and do not themselves impose any restrictions or additional technical requirements beyond those contained in relevant EC Directives Alternative approaches may be acceptable but the guidance provided in this do
86. ion to the guidance for risk classes B and C e Check whether measures taken for guaranteeing the authenticity of transmitted data are appropriate 47 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 Risk Class B Risk Class C Risk Class D T5 Confidentiality of keys Keys and accompanying data must be treated as legally relevant data and must be kept secret and be ie Notes This requirement only applies if a secret key exists in the system Normally not in Closed networks 2 The protection must apply against intentional changes carried out by common simple software tools 3 If the access to the secret keys is prevented e g by sealing the housing of a built for purpose device no additional software protection means are necessary le Notes This requirement only applies if a secret key exists in the system Normally not in Closed networks The protection must apply against intentional changes carried out by special sophisticated software tools The received measurement values are read from the data set and their signature is checked with the aid of the public key of the sending measuring instrument or the device that generated the relevant data set With this check the receiver can prove that value and signature belong together Appropriate methods equivalent electronic payment shall be used 4 to Required Documentation Description of the key management and means for
87. is stored in the fixed software part before initial verification 3 Correct type of measuring instrument Checking the instrument type requires automatically matching an identification of instrument type that is stored in the fixed software part of the instrument with a compatibility list attached to the ore Software ee 4 NB Approval 4 NB Approval If authenticity is guaranteed through the use of To check that software has been genuinely the manufacturer s key then NB approval may be approved one solution is that all assumed downloaded approved software contains the responsible authority s signature The responsible authority s public key is stored in the measuring instrument and is used to automatically check the signature attached to the software It can be visualised at the instrument for comparison with the key published by the responsible authority Additions for Risk Class E Required Documentation in addition to the documentation required for risk classes B and C Source code of the fixed software part responsible for checking the authenticity of the downloaded software Validation Guidance in addition to the guidance for risk classes B and C Checks based on the source code e Check whether measures taken for checking the authenticity are appropriate 58 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 Risk Class D Risk Class B Required Documentation
88. ked required for risk classes B and to the software itself how it may be accessed for viewing and how it is C structured in order to differentiate between version changes with and The documentation shall show without requiring a type approval the measures taken to protect the software identification from falsification Validation Guidance Validation Guidance in addition Checks based on documentation to the guidance for risk classes B e Examine description of the generation and visualisation of the 2d software identification Checks based on documentation e Check whether all programs performing legally relevant functions e Check whether the measures are clearly identified and described so that it is clear to both Notified taken to protect from Body and manufacturer which software functions are covered by falsification are appropriate the software identification and which are not e Check whether a nominal value of the identification version number or functional checksum is supplied by the manufacturer This must be quoted in the test certificate Functional Checks e The software identification can be visualised as described in the documentation e The presented identification is correct The documentation plus the executable code if necessary of the pattern is kept at the NB 16 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 e Part A of the identification consists of a version number
89. l contain a protocol that shows the tests of all commands Validation Guidance Checks based on documentation e Judge that documented commands are admissible i e that they have an allowed impact on the measuring functions and relevant data or none at all e Check that manufacturer has supplied an explicit declaration of completeness of the command documentation Functional checks e Carry out practical tests spot checks with both documented and undocumented commands Test all menu items if any Validation Guidance in addition to the guidance for risk classes B and C Checks based on documentation e Check whether the measures taken and test protocols are appropriate for the high protection level Acceptable Solution e A module in the legally relevant software filters out inadmissible commands Only this module receives commands and there is no circumvention of it Any false input is blocked The user is controlled or guided when inputting commands by a special software module This guiding module is The access to the operating system is blocked Additions for Risk Class E Required Documentation in addition to the documentation required for risk classes B and C Source code of the legally relevant software Validation Guidance in addition to the guidance for risk classes B and C Checks based on the source code e Check the software design whether dat
90. led electricaly and the means for disabling can be the art for a high protection secured sealed For checking download facilities see extension level D Functional checks e Test practically the programming mode and check whether disabling works Example of an Acceptable Solution The instrument is sealed and the interfaces comply with the requirements P3 and P4 Additions for Risk Class E Required Documentation in addition to the documentation required for risk classes B and C Source code of the instrument Validation Guidance in addition to the guidance for risk classes B and C Checks based on the source code e Check in the source code whether measures taken for the detection of intentional changes are appropriate 21 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 Risk Class B Risk Class C Risk Class D P7 Parameter protection Parameters that fix legally relevant characteristics of the measuring instrument shall be secured against unauthorised modification Specifying Notes 1 Type specific parameters are identical for each specimen of the type and are in general part of the program code Therefore requirement P6 applies to them 2 Device specific secured parameters may be changed using an on board keypad or switches or via interfaces but only before they have been secured 3 Settable device specific parameters may be changed after securing Required Documentatio
91. ly addressed indirectly as the programmer of software parts that are not subject to legal control must not give the user of the measuring system the opportunity of corruption But this has in any case to be considered by the programmer with or without separation and the appropriate requirements are given in the basic parts P and U Chapter 4 and 5 of the guide 51 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 8 2 Specific software requirements for software separation Risk Class B Risk Class C Risk Class D S1 Realisation of software separation There shall be a part of the software that contains all legally relevant software and parameters that is a Notes In the case of low level separation all program units subroutines procedures functions classes etc and in case of high level separation all programs and libraries that contribute to the calculation of measurement values or have an impact on it that contribute to auxiliary functions such as displaying data data security data storage software identification performing software download data transmission or storing verifying received or stored data etc belong to the legally relevant software 2 All variables temporary files and parameters that have an impact on measurement value or on legally relevant functions or data belong to the legally relevant software 3 The components of a protective software interface see S3 are part of the legally rel
92. methodology that allows the manufacturer to easily modify non legally relevant software If software separation is implemented then this extension shall be considered in addition to the basic requirements for types P and U 8 1 Technical description Software controlled measuring instruments or systems in general have complex functionality and contain modules that are legally relevant and modules that are not It is advantageous for the manufacturer and examiner though it is not prescribed to separate these software modules of the measuring system In the following table two variants of software separation are described Both variants are covered by the set of requirements Description Software separation is realised independently from the operating system within an application domain i e at the programming language level Low level software separation Note This feature is realisable in both built for purpose devices and universal computers The software modules to be separated are realised as independent objects in terms of the operating system High level software separation Note This type of separation is normally possible only with universal computers Example solutions are independently executable programs dynamically linked libraries etc Table 8 1 Technical description of a Type U measuring instrument The protection against inadmissible changes of measurement values and parameters is on
93. n Required Documentation in The documentation should describe all of the legally relevant ddition to the documentation parameters their ranges and nominal values where they are equired for risk classes B and C stored how they may be viewed how they are secured and when The protection measures taken for i e before or after verification parameters shall be shown Validation Guidance Validation Guidance in addition to Checks based on documentation the guidance for risk classes B and e Check that changing or adjusting secured device specific oF ae parameters is impossible after securing Checks based on documentation Check whether all relevant parameters according to the lists Check whether the measures given in Extension if any have been classified as secured taken are appropriate with Funcnonalchecke respect to the required state of the art for a high protection e Test the adjusting configuration mode and check whether level disabling after securing works e Examine the classification and state of parameters secured settable at the display of the instrument if a suitable menu item is provided Example of an Acceptable Solution a Parameters are secured by sealing the instrument or memory housing and disabling the write enable disable input of the memory circuit by an associated jumper or switch which is sealed Audit trails b An event counter registers each change of a param
94. n level e Test the adjusting configuration mode and check whether disabling after securing works e Examine the classification and state of parameters secured settable at the display of the instrument if a suitable menu item is provided The TAC should list those parameters that are settable and how they may be located Example of an Acceptable Solution e Device specific parameters are stored on a plugged in storage which is sealed against removing or directly on the sensor unit Writing of parameters is inhibited by sealing a write enable switch in the disabled state Audit trails are possible in combination with securing hardware see P7 e Settable parameters are stored on a standard storage of the universal computer Additions for Risk Class E Required Documentation in addition to the documentation required for risk classes B and C Source code of the instrument Validation Guidance in addition to the guidance for risk classes B and C Checks based on the source code e Check whether measures taken for protecting parameters are appropriate 31 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 Risk Class B Risk Class C Risk Class D U8 Software authenticity and presentation of results Means shall be employed to ensure the authenticity of the legally relevant software The authenticity of the results that are presented shall be guaranteed Specifying Notes
95. nload attempt regardless of the success After having reached the limit of the event logger it shall be ensured by technical means that further downloads are impossible Audit trails may only be erased by breaking a physical or electronic seal and may be resealed only by the inspection authorities Additions for Risk Class E Required Documentation in addition to the documentation required for risk classes B and C Source code of the fixed software part responsible for tracing download processes and managing the audit trail Validation Guidance in addition to the guidance for risk classes B and C Checks based on the source code e Check whether measures taken for tracing the download process are appropriate e Check whether measures taken for protecting the audit trail are appropriate 60 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 Risk Class B Risk Class C Risk Class D D5 Download consent It shall be guaranteed by technical means that software may u be loaded with the explicit consent of a Notes Once an instrument has been put into service the user or its owner is responsible for it This requirement ensures that the manufacturer cannot change the legally relevant software of the instrument without the explicit consent of the appropriate responsible party 2 The means by which the user owner expresses his consent are part of the legally relevant software and should be protected as su
96. nt software and measurement data shall be protected against accidental or unintentional Specifying Notes Possible reasons for accidental changes and faults are unpredictable physical influences effects caused by user functions and residual defects of the software even though state of the art of development techniques have been applied This requirement includes a Physical influences Stored measurement data shall be protected against corruption or deletion when a fault occurs or alternatively the fault shall be detectable b User functions Confirmation shall be demanded before deleting or changing data c Software defects Appropriate measures shall be taken to protect data from unintentional changes that could occur through incorrect program design or programming errors e g plausibility checks Required Documentation The documentation should show the measures that have been taken to protect the software and data against unintentional changes Validation Guidance Checks based on documentation e Check that a checksum of the program code and the relevant parameters is generated and verified automatically e Check that overwriting of data cannot occur before the end of the data storage period that is foreseen and documented by the manufacturer e Check that a warning is issued to the user if he is about to delete measurement data files Functional checks e Check by practical spot checks that before deleting measurement
97. ntation in addition to the documentation required for risk classes B and C Source code of the legally relevant software Validation Guidance in addition to the guidance for risk classes B and C Checks based on the source code e Check the software design whether data flow is unambiguously defined in the legally relevant software and can be verified e Check the data flow via the software interface with tools or manually Check whether all data flow between the parts has been documented no circumvention of the declared software interface Search inadmissible data flow from the part not subject to control to domains to be protected e Check that commands if any are decoded correctly and no undocumented commands exist 54 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 9 Extension D Download of Legally Relevant Software This extension shall be used for the download of legally relevant software e g bug fixes updates new applications etc to measuring instruments of both types P and U as appropriate These requirements are to be considered in addition to the basic requirements for Types P and Type U described in Chapters 4 and 5 in the guide 9 1 Technical Description Software may be downloaded only to measuring instruments that are characterised by the following properties Hardware Configuration The target device is subject to legal control It may be a built for purpose measuring instrument T
98. ntrol if the presentation of results is easily distinguishable from other information that may also be presented e Check according to the documentation if the presented information is complete Validation Guidance in addition to the guidance for risk classes B and C Checks based documentation e Check whether the measures taken are appropriate with respect to the required state of the art for a high protection level on 32 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 Example of an Acceptable Solution Formal means 1 The software identification part B checksum version number or TAC number see U2 indicated by the software is compared with the desired value in the TAC Technical means 1 A measurement application window is generated by the legally relevant software The technical measures required of the window are e No access to measurement values shall be given to non legally relevant programs until the measurement values have been indicated e The window is refreshed periodically The associated program checks that it is always visible e Processing of measurement values stops whenever this window is closed or not completely visible The operating manual and TAC should contain a copy of the window for reference purposes 2a The sensor unit encrypts the measuring values with a key known to the approved software running on the universal computer e g its version number Only the approved s
99. of the storage subject to legal control has been certified by an accredited Trust Centre Direct Trust It is not necessary to involve a trust centre if by prior agreement both parties are able to read the public key of the measuring instrument directly at a device subject to legal control that is displaying the relevant data set 2 48 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 Additions for Risk Class E Required Documentation in addition to the documentation required for risk classes B and C Source code that realises key management Validation Guidance in addition to the guidance for risk classes B and C Checks based on the source code e Check whether measures taken for key management are appropriate Risk Class B Risk Class C Risk Class D T6 Handling of corrupted data Specifying Notes 1 Though communication protocols normally repeat transmission until it succeeds it nevertheless is possible that a corrupted data set is received Required Documentation Required Documentation in addition to the Description of the detection of transmission faults or ocumentation required for risk classes B intentional changes and C The measures taken for correct handling of corrupted data shall be shown Validation Guidance Validation Guidance in addition to the Checks based on documentation and functional checks guidance for risk classes B and C e Check that th
100. oftware can decrypt and use the measurement values non approved programs on the universal computer cannot as they don t know the key For key treatment see Extension T 2b Before sending measurement values the sensor initiates a handshake sequence with the legally relevant software on the universal computer based on secret keys Only if the program on the universal computer communicates correctly the sensor unit sends its measurement values For key treatment see Extension T 3 The key used in 2a 2b may be 3 The key used in 2a 2b is the hash code of the program chosen and entered to the sensor on the universal computer Each time the software on the unit and software on the universal universal computer is changed the new key has to be computer without destroying a seal entered into the sensor unit and sealed Additions for Risk Class E Required Documentation in addition to the documentation required for risk classes B and C Source code of the legally relevant software Validation Guidance in addition to the guidance for risk classes B and C Checks based on the source code e Check that legally relevant software generates the presented measurement results e Check whether all measures taken are appropriate and correct to guarantee the authenticity of the software e g that legally relevant tasks can only be performed by the approved legally relevant software Risk Classes B to E U9 Influen
101. ological surveillance of legally controlled instruments to back trace downloads of legally relevant software over an adequate period of time that depends on national legislation 2 The traceability means and records are part of the legally relevant software and should be protected as such Required Documentation The documentation shall e Briefly describe how the implemented and protected e State how downloaded software may be traced traceability means is Required Documentation in addition to the documentation required for risk classes B and C The measures of ensuring traceability shall be shown by the documentation Validation Guidance Checks based on documentation e Check that traceability means are implemented and protected Functional checks e Check the functionality of the means through spot checks Validation Guidance in addition to the guidance for risk classes B and C Checks based on documentation e Check whether the measures taken are appropriate with respect to the required state of the art for a high protection level Example of an Acceptable Solution e An audit trail The measuring instrument may be equipped with an event logger that automatically records at least the date and time of the download identification of the downloaded legally relevant software the identification of the downloading party and an entry of the success An entry is generated for each dow
102. omatically when the operator accepts the result 3 For the case of full storage refer to requirement L8 Required Documentation Confirmation that storing is automatically carried out Description of the Graphical User Interface Validation Guidance Functional checks e Examine by spot checks that the measurement values are stored automatically after measurement or acceptance of measurement is concluded Check that there are no buttons or menu items to interrupt or disable the automatic storing Example of an Acceptable Solution There is no menu item or button in the Graphical User Interface GUI that supports manual initiation of storing measurement results The measurement values are wrapped in a data set along with additional information such as time stamp and signature and are stored immediately after the measurement or the acceptance of measurement respectively Additions for Risk Class E Required Documentation in addition to the documentation required for risk classes B C and D Source code of the instrument Validation Guidance in addition to the guidance for risk classes B C and D Checks based on the source code e Check whether measures taken for automatic storing are appropriate and correctly implemented 41 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 Risk Class B Risk Class C Risk Class D L8 Storage capacity and continuity Specifying Notes 1 When
103. on delay Validation Guidance e Check the concept that the measurement is not influenced by transmission delay Example of an Acceptable Solution Implementation of transmission protocols for field buses 49 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 Additions for Risk Class E Required Documentation in addition to the documentation required for risk classes B C and D Source code that realises the data transmission Validation Guidance in addition to the guidance for risk classes B C and D Checks based on the source code e Check whether measures taken for handling transmission delay are appropriate Risk Class B Risk Class C Risk Class D T8 Availability of transmission services agenda Notes The user of the measuring system must not be able to corrupt measurement data by suppressing transmission 2 Transmission disturbances happen accidentally and cannot be excluded The sending device must be able to handle this situation 3 The reaction of the instrument if transmission services become unavailable depends on the measuring principle see Part Required Documentation Description of protection measures against transmission interruption or other failures Validation Guidance Checks based on documentation e Check by what measures are implemented to protect from data loss e Check which measures are foreseen for the case of transmission failu
104. on sealed communication interfaces of the instrument prevented from inadmissibly influencing the legally relevant software and measurement data ps Are legally relevant software and measurement data protected against accidental or unintentional changes P6 moainsaion acing or swapping ot hardnare memory modification loading or swapping of hardware memory Are parameters that fix legally relevant characteristics of the P7 measuring instrument secured against unauthorised modification Explanations are needed if there are deviations from software requirements c E oO m 5 cc 2 a is 2 2 2 lt z 2 Checklist for basic requirements for type U instrument Checklist for Type U Requirements Does the required manufacturer s documentation fulfil the A requirement U1 a h Are commands entered via the user interface prevented from inadmissibly influencing the legally relevant software and measurement data it prevented that commands inputted via non sealed communication interfaces of the instrument inadmissibly influence the legally relevant software and measurement data Are legally relevant software and measurement data protected il against accidental or unintentional changes Are legally relevant software secured against inadmissible modification Are legally relevant parameters secured against unauthorised u modification 2 a 2 2 2 lt Z Se a 8 Ref 105
105. ons and data of the measuring instrument Required Documentation in addition to the documentation required for risk classes B and C The documentation shall show the measures taken to validate the completeness of the documentation of commands e The documentation shall contain a protocol that shows the tests of all commands Validation Guidance Validation Guidance in Checks based on documentation e Judge whether all documented commands are admissible i e whether they have an allowed impact on the measuring functions and relevant data or none at all e Check whether the manufacturer has supplied an explicit declaration of completeness of the command documentation Functional Checks e Carry out practical tests spot checks with both documented and undocumented commands Test all menu items if any addition to the guidance for risk classes B and C Checks based on documentation e Check whether the measures taken and test protocols are appropriate for the high protection level Example of an Acceptable Solution There is a software module that receives and interprets commands from the user interface This module belongs to the legally relevant software It only forwards allowed commands to the other legally relevant software modules All unknown or not allowed sequences of switch or key actuations are rejected and have no impact on the legally relevant software or measurement data
106. or the number of the TAC Additions for Risk Class E Required Documentation in addition to the documentation required for risk classes Band C Source code that contains the generation of the identification Validation Guidance in addition to the guidance for risk classes B and C Checks based on the source code e Check whether all relevant software parts are covered by the algorithm for generating the identification e Check the correct implementation of the algorithm 17 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 Risk Class B Risk Class C Risk Class D P3 Influence via user interface Commands entered via the user interface shall not inadmissibly influence the legally relevant software and measurement data Specifying Notes 1 Commands may be one single or a sequence of switch or key actuations carried out manually 2 This implies that there is an unambiguous assignment of each command to an initiated function or data change 3 This implies that switch or key actuations that are not declared and documented as commands have no effect on the instrument s functions and measurement data Required Documentation If the instrument has the ability to receive commands the documentation shall include e A complete list of all commands e g menu items together with a declaration of completeness A brief description of their meaning and their effect on the functi
107. ormation Example of an Acceptable Solution The data set is read from the storage by the verifying program and the signature over all data fields is recalculated and compared with the stored nominal value If both values match the data set is correct otherwise the data are not used and are deleted or marked invalid by the program Additions for Risk Class E Required Documentation in addition to the documentation required for risk classes B and C Source code of the retrieval program Validation Guidance in addition to the guidance for risk classes B and C Checks based on the source code e Check whether measures taken for retrieval verification of signatures etc are appropriate and correctly implemented 40 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 Risk Class B Risk Class C Risk Class D L7 Automatic storing Specifying Notes 1 This requirement applies to all types of storage 2 This requirement means that the storing function must not depend on the decision of the operator Nevertheless in some types of instrument e g weighing instruments a decision or command is required from the operator whether or not to accept the result In other words there might be some intermediate measurements that will not be stored for example during loading or before the quantity of product requested is on the load receptor However even in this case the result will be stored aut
108. ould have a key length of at least 2 bytes a CRC 16 checksum with a secret initial vector hidden in the executable code would be satisfactory See also Extensions L and T e The unauthorised manipulation of legally relevant software may be controlled by the access control or privacy protection attributes of the operating system The administration level of these systems shall be secured by sealing or equivalent means Example of Acceptable Solution Program code may be secured by storing the legally relevant software in a dedicated plug in unit which is sealed The plug in unit may include for example a read only memory and a microcontroller an Additions for Risk Class E Required Documentation in addition to the documentation required for risk classes B and C Source code of the instrument Validation Guidance in addition to the guidance required for risk classes B and C Checks based on the source code e Check communication with the additional securing hardware e Check that changes of programs or data are detected and program execution stops in this case 30 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 Risk Class B Risk Class C Risk Class D U7 Parameter protection Specifying Notes 1 Type specific parameters are identical for each specimen of the type and are in general part of the program code i e part of the legally relevant software Therefore requir
109. portant for software IT functions of the measuring instruments including infrared Bluetooth Wireless LAN e Identification and description of locations of software components in the measuring instrument i e EPROM processor hard disk that need to be sealed or secured e Instructions of how to check the identification of software for metrological supervision e Incase of electronic sealing instruction for the inspection of audit trails 108 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 13 Cross Reference for MID Software Requirements to MID Articles and Annexes Related MID Version Directive 2004 22 EC 31 March 2004 13 1 Given software requirement reference to MID Requirement MID No Denotation Article Annex No Denotation Al Annex Basic Guide P P1 Manufacturer s Documenta Al 9 3 Information to be borne by and to tion accompany the instrument Al 12 Conformity Evaluation Article 10 Technical Documentation P2 Software Identification Al 7 6 Suitability Al 8 3 Protection against corruption P3 Influence via User Interface __ Al 7 1 Suitability P4 Influence via communication Al 7 1 Suitability Interface Al 8 1 Protection against corruption P5 Protection Against Accidental Al 7 1 Al 7 2 Suitability or Unintentional Changes Al 8 4 Protection against corruption P6 Protection Against Intentional Al 7 1 Suit
110. protection measures e g the checksum algorithm addition to the documentation including the length of the generator polynomial required for risk classes B and C The documentation shall show the measures taken to validate the effectiveness of the protection means Validation Guidance Validation Guidance in addition Checks based on documentation to the guidance for risk classes B and C e Check that a checksum over data is generated e Check that legally relevant software which reads the data and Checks based on documentation calculate a checksum really compares the calculated and the Check whether the measures nominal values taken are appropriate for the e Check that overwriting of data cannot occur before the end of the high protection level data storage period that is foreseen and documented by the manufacturer e Check that a warning is issued to the user if he is about to delete measurement data files Functional checks e Check by practical spot checks that before deleting measurement data a warning is given if deleting is possible at all Example of an Acceptable Solution e To detect data changes due to physical effects a checksum with the CRC 16 algorithm is calculated over the entire data set and inserted into the data set to be stored Note The algorithm is not secret and in contrast to requirement L3 neither is the initial vector of the CRC register nor the generator polynomial i e
111. proved by an NB Are means employed to guarantee that the downloaded software has not been inadmissibly changed during download Is it guaranteed by appropriate technical means that downloads of legally relevant software are adequately traceable within the instrument for subsequent controls Is it guaranteed by technical means that software may only be loaded with the explicit consent of the user or owner of the measuring instrument as appropriate Explanations are needed if there are deviations from software requirements c E o 5 gt o 12 4 Information to be included in the type approval certificate While the entire test report is a documentation of the object under test the validation carried out and the results a certain selection of the information contained in the test report are required for type approval certificate TAC This concerns the following information which should be appropriately included in the TAC e Reference to the documentation submitted for type approval e Identification and description of the electronic hardware components subassemblies modules that are important for software IT function of the measuring instruments e Overview of the software environment which is necessary to operate the software e Overview of SW modules under legal control including SW separation if implemented e Overview and identification of hardware and software if relevant interfaces that are im
112. r a built for purpose device the variant of an integrated storage is typical here the storage is part of the metrologically necessary hardware and software For instruments using a universal computer another variant is typical the use of resources already existing e g hard disks The third variant is the removable storage here the storage can be removed from the device which could be either a built for purpose device or a universal computer and be taken elsewhere When data is retrieved from removable storage for legal purposes e g visualisation ticket printing etc the retrieving device shall be subject to legal control Integrated storage Simple instrument built for purpose no externally usable tools or means available for editing or changing data integrated storage for measurement data or parameters e g RAM flash memory hard disk Storage for universal computer Universal computer graphical user interface multitasking operating system tasks subject to legal control and not subject to legal control exist in parallel storage can be removed from the device or contents can be copied anywhere inside or outside the computer Removable or remote external storage Arbitrary basic instrument built for purpose instrument or instrument using universal computer storage can be taken from the instrument These can be for example floppy disks flash cards or remote databases connected via network Table 6 1
113. rce code of the instrument Validation Guidance in addition to the guidance for risk classes B and C Checks based on the source code e Check whether measures taken for detection of changes faults are appropriate e Ifa checksum is realised check whether all parts of the legally relevant software are covered by it 29 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 Risk Class B Risk Class C Risk Class D U6 Protection against intentional changes Legally relevant software and measurement data shall be secured against inadmissible modification Specifying Notes 1 Changes with the intention of fraud could be attempted by a Changing the program code including integrated data if the program code is an executable format exe then it is sufficiently protected for risk classes B and C b Changing the measurement data refer to Extension L 2 Exchange of the approved software shall not be possible simply by using the operating system e g to load and use non approved software instead see e g U3 For downloading software see Extension D 3 Where necessary means shall be taken to protect legally relevant software against modification by simple tools e g text or window editors Specifying Notes 1 The level of protection should be equivalent to that of electronic payments In general a universal computer is only suitable for this risk class with additional hardware for
114. re Functional checks e Spot checks shall show that no relevant data get lost due to a transmission interruption Example of an Acceptable Solution 1 For interruptible measurements that can be stopped easily and rapidly e g weighing fuel measurement etc the measurement may be completed even though the transmission is down However the measuring instrument or the device that is transmitting the legally relevant data must have a buffer that is large enough to store the current transaction After this no new transaction may be started and the buffered values are kept for later transmission For other examples see part I 2 Measurements that are not interruptible e g the measurement of energy volume etc do not need a special intermediate buffer because these measurements always are cumulative The cumulative register can be read out and transmitted at a later time when the connection is up again Additions for Risk Class E Required Documentation in addition to the documentation required for risk classes B C and D Source code that realises data transmission Validation Guidance in addition to the guidance for risk classes B C and D Checks based on the source code e Check whether measures taken for reacting on interrupted transmission service are appropriate 50 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 8 Extension S Software Separation Software separation is an optional design
115. red state of the art for a high protection level Example of an Acceptable Solution e A checksum is generated of the data set to be transmitted Just before the data is reused the value of the checksum is recalculated and compared with the nominal value that is contained in the received data set If the values match the data set is valid and may be used otherwise it must be deleted or marked invalid e An acceptable solution is the CRC 16 algorithm Note The algorithm is not secret but in contrast to requirement T2 the initial vector of the CRC register or the generator polynomial i e the divisor in the algorithm are secret The initial vector and generator polynomial are known only to the programs generating and verifying the checksums They must be treated as keys see T5 Example of an Acceptable Solution e Instead of the CRC a signature is calculated A suitable signature algorithm would be e g one of the hash algorithms SHA 1 or RipeMD 160 in combination with an encryption algorithm like RSA or Elliptic Curves The minimum key length is 768 bits RSA or 128 160 bits EC Protection is provided by some transmission protocols e g HTTPS 46 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 Additions for Risk Class E Required Documentation in addition to the documentation required for risk classes B and C Source code that realises the integrity of transmitted data Valid
116. rised in Table 5 1 below Basically a Type U system must be assumed if the conditions of a type P instrument see Chapter 4 1 are not fulfilled Hardware Configuration a A modular general purpose computer based system The computer system may be stand alone part of a closed network e g Ethernet token ring LAN or part of an open network e g Internet b Because the system is general purpose the sensor would normally be external to the computer unit and would normally be linked to it by a closed communications link The communication link could however also be open e g network whereby several sensors could be connected c The user interface may be switched from an operating mode which is not under legal control to one which is and vice versa d Storage may be local e g hard disk or remote e g file server Remote storage may be located anywhere e g in the same building or even in a different country which could be outside the EU Thus the communications link to storage devices may be direct which permits handshaking or indirect whereby there might be an intermediate storage phase not under the control of the user e g dial up on Internet Storage may be fixed e g hard disk or removable e g diskettes CD RW Software Configuration e Any operating system may be used In addition to the measuring instrument application other software applications may also reside on the system at the same time Par
117. rk completely under legal control Only a fixed number of participants with clear identity functionality and location are connected All devices are subject to legal control No devices exist in the network that are not subject to legal control Closed network partly under legal control A fixed number of participants with clear identity and location are connected to the network Not all devices are subject to legal control and therefore their functionality is unknown Open network Arbitrary participants devices with arbitrary functions can connect to the network The identity and functionality of a participating device and its location may be unknown to other participants Any network that contains legally controlled devices with IR or wireless network communications interfaces shall be considered to be an open network Table 7 1 Technical description of a Type U measuring instrument 43 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 7 2 Specific software Requirements for Data Transmission Risk Class B Risk Class C Risk Class D T1 Completeness of transmitted data The transmitted data must contain all relevant information necessary to present or further process the Specifying Notes 1 The metrological part of a transmitted data set comprises one or more measurement values with correct resolution the legally correct unit of measure and depending on the application the unit price or the price to pay and
118. ronment Public Key System PKS A pair of two different signature keys one called the secret key and the other the public key To verify integrity and authenticity of information the hash value of the information generated by a hash algorithm is encrypted with the secret key of the sender to create the signature which is decrypted later by the receiver using the sender s public key PKI Infrastructure Organisation to guarantee the trustworthiness of a public key system This includes granting and distributing digital certificates to all members that take part in the information exchange Certification of keys The process of binding a public key value to an individual organisation or other entity Electronic signature A short code the signature that is unambiguously assigned to a text data block or binary software file to prove the integrity and authenticity of data stored or transmitted The signature is created using a signature algorithm and a secret signature key Usually the generation of an electronic signature is composed of two steps 1 first a hash algorithm compresses the contents of the information to be signed to a short value and 2 then a signature algorithm combines this number with the secret key to generate the signature Trust Centre An association that trustworthily generates keeps and issues information about the authenticity of public keys of persons or other entities e g measuring instruments WELMEC
119. s that are not described in the documentation Validation Guidance in addition to the guidance for risk classes B and C Checks based on documentation e Check whether the measures taken and test protocols are appropriate for the high protection level Example of an Acceptable Solution There is a software module that receives and interprets data from the interface This module is part of the legally relevant software It only forwards allowed commands to the other legally relevant software modules All unknown or not allowed signal or code sequences are rejected and have no impact on the legally relevant software or measurement data 19 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 Additions for Risk Class E Required Documentation in addition to the documentation required for risk classes B and C Source code of the instrument Validation Guidance in addition to the guidance for risk classes B and C Checks based on the source code e Check the software design whether data flow concerning commands is unambiguously defined in the legally relevant software and can be verified e Search inadmissible data flow from the interface to domains to be protected e Check with tools or manually that commands are decoded correctly and no undocumented commands exist Risk Class B Risk Class C Risk Class D P5 Protection against accidental or unintentional changes Legally releva
120. s the instrument belongs to 3 2 How to select the appropriate parts of the guide This comprehensive software guide is applicable to a large variety of instruments The guide is modular in form The appropriate requirement sets can be easily selected by observing the following procedure Step 1 Selection of the basic configuration P or U Only one of the two requirement sets for basic configurations needs to be applied Decide which basic configuration the instrument conforms to a built for purpose instrument with imbedded software type P see Chapter 4 1 or an instrument using a universal computer type U see Chapter 5 1 If not the whole instrument but only a component of the instrument is the matter of concern then decide accordingly for the component Apply the complete set of requirements that belongs to the respective basic configuration Step 2 Selection of applicable IT configurations extensions L T S and D The IT configurations comprise long term storage of legally relevant data L transmission of legally relevant data T software separation S and download of legally relevant software D The corresponding requirement sets called modular extensions are independent of each other The sets selected depend only on the IT configuration If an extension set is selected then it must be applied in full Decide which if any of the modular extensions are applicable and apply them accordingly Figure 3 2 Step 3 S
121. son to risk class A 98 WELMEC WG7 Risk class D Risk class E Risk class F Software Guide WELMEC 7 2 Issue 1 The significant difference in comparison to risk class C is the upgrade of the protection level to high Since the examination level remains unaffected at middle sufficiently informative documentation must be provided to show that the protection measures taken are appropriate The conformity level remains unchanged in comparison to risk class C In comparison to risk class D the examination level is upgraded to high The levels of protection and conformity remain unchanged The levels with respect to all aspects protection examination and conformity are set to high Like risk class A it is not expected that any instrument is classified as a risk F instrument However by introducing this class the corresponding possibility is held open 99 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 12 Pattern for Test Report Including Checklists This is a pattern for a test report which consists of a main part and two annexes The main part contains general statements on the object under test It must be correspondingly adapted in practice The annex 1 consists of two checklists to support the selection of the appropriate parts of the guide to be applied The annex 2 consists of specific checklists for the respective technical parts of the guide They are recommended as an aid for manufactur
122. t this happening either the housing of the instrument should be secured or the physical memory itself is secured against unauthorised removal 2 Instrument with interface The interface shall include only functions which are subject to examination All functions in the interface shall be subject to examination see P4 Where the interface is to be used for software download extension D must be complied with 3 Data are considered to be sufficiently protected if only legally relevant software processes them If non legally relevant Software is intended to be changed after approval requirements of extension S have to be followed Required Documentation Required Documentation in The documentation shall provide assurance that legally relevant addition to the documentation software cannot be inadmissibly modified required for risk classes B and C The protection measures taken to protect from intentional changes shall be shown Validation Guidance Validation Guidance in addition Checks based on documentation to the guidance for risk classes B and C e Examine whether the documented means of securing against unauthorised exchange of the memory that contains the software Checks based on documentation are sufficient e Check whether the measures e If the memory can be programmed in circuit without taken are appropriate with dismounting check whether the programming mode can be respect to the required state of disab
123. ta stored to the disputed measurement without ambiguity refer also L1 L3 L4 and L5 2 The identification number see L1 must be printed out on the delivery note ticket for the customer along with an explanation and a reference to the storage subject to legal control 3 Verification means checking the integrity authenticity and correct assignment of the measurement data stored 4 The verification software used for displaying or printing the data stored shall be subject to legal control 5 For instrument specific requirements refer to Extension Required Documentation Required Documentation in addition to e Description of the functions of the retrieval program the documentation required for risk classes Description of detection of corruption B and C Operating manual for this program The protection measures taken shall be shown Validation Guidance Validation Guidance in addition to the Checks based on documentation guidance for risk classes B and C e Check that retrieval software really compares the Checks based on documentation calculated and the nominal values e Check whether the measures taken are e Check that retrieval software is part of the legally relevant appropriate with respect to the required software state of the art for a high protection Functional checks level e Check whether the program detects corrupted data sets e Perform spot checks verifying that retrieval provides all necessary inf
124. that this indication cannot be changed or suppressed by non legally relevant programs 53 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 Risk Class B Risk Class C Risk Class D S3 Protective software interface The data exchange between the legally relevant and non legally relevant software must be performed Specifying Notes 1 All interactions and data flows shall not inadmissibly influence the legally relevant software including the dynamic behaviour of a measuring process 2 There shall be an unambiguous assignment of each command sent via the software interface to the initiated function or data change in the legally relevant software 3 Codes and data that are not declared and documented as commands must not have any effect on the legally relevant software 4 The interface shall be completely documented and any other non documented interaction or data flow circumvention of the interface must not be realised neither by the programmer of the legally relevant software nor by the programmers of the non legally relevant software Note The programmers are responsible for observing these constraints Technical means to prevent them from circumventing the software interface are not possible The programmer of the protective interface should be instructed about this requirement Required Documentation Required Documentation in e Description of the software interface especially which data addition to the do
125. the devisor in the algorithm The initial vector and generator polynomial are known to both of the programs that create and verify the checksums e Measurement data invoice files could be protected by attaching an automatic date stamp on creation and a flag or label stating whether invoices were paid unpaid A utility program would only delete move files if invoices had been paid or were out of date e Measurement data are not deleted without prior authorisation e g a dialogue statement or window asking for confirmation of deletion Additions for Risk Class E Required Documentation in addition to the documentation required for risk classes B C and D Source code that realises the protection of stored data Validation Guidance in addition to the guidance for risk classes B C and D Checks based on the source code e Check whether measures taken for protecting stored date are appropriate and correctly implemented 36 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 Risk Class B Risk Class C Risk Class D L3 Integrity of data The measurement data stored must be protected against intentional changes nn Notes This requirement applies to all types of storages except integrated storages 2 The protection must apply against intentional changes carried out by simple common software tools 3 Simple common software tools are understood as tools which are easily available and manage
126. the original status of the measuring instrument shall be unaffected Alternatively the instrument shall display a permanent error message and its metrological functioning shall be inhibited until the cause of the error is corrected 4 On successful completion of the installation all protective means should be restored to their original state unless the downloaded software has NB authorisation in the TAC to amend them 5 During download and the subsequent installation of downloaded software measurement by the instrument shall be inhibited or correct measurement shall be guaranteed 6 The fault handling requirements described in Extension may be implemented if faults occur during downloading The number of re installation attempts shall be limited 7 If the requirements D2 to D5 cannot be fulfilled it is still possible to download the non legally relevant software part In this case the following requirements shall be met There is a distinct separation between the legally relevant and non relevant software according to Extension S e The whole legally relevant software part is fixed i e it cannot be downloaded or changed without breaking a seal e Itis stated in the TAC downloading of the non legally relevant part is acceptable Required Documentation Required Documentation in The documentation should briefly describe the automatic nature of addition to the documentation the download checking installation how the level o
127. the requirements of the part P Chapter 4 apply In all other cases the requirements of the part U Chapter 5 are necessarily to apply Decision on Required Extensions Not Applicable The second checklist supports to decide which of the IT configuration applies for the instrument under test n i Does the device have the ability to store the measurement data L either on an integrated storage or on a remote or removable storage Does the device have interfaces for transmission of data to devices subject to legal control OR is the device receiving data from another device subject to legal control Are there software parts with functions not subject to legal control AND are these software parts desired to be changed after type approval KECE D Is loading of software possible or desired ee a Consider the required extension for each question answered with YES Consider the required extension for each question answered with YES 104 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 12 3 Annex 2 of the test report Specific checklists for the respective technical parts 1 Checklist of basic requirements for type P instrument Checklist for Type P Requirements ee f le ee Passed Does the required manufacturer documentation fulfil the requirement P1 a g Are commands entered via the user interface prevented from inadmissibly influencing the legally relevant software and measurement data Are commands input via n
128. tion to the documentation required for risk classes B and C The protection measures taken shall be shown Validation Guidance Checks based on documentation e Check that there is a correct linking between each measurement value and the corresponding measurement e Check that data are digitally signed to ensure their proper identification and authentication Validation Guidance in addition to the guidance for risk classes B and C Checks based on documentation e Check whether the measures taken are appropriate with respect to the required state of the art for a high protection level Example of an Acceptable Solution measurement has been performed time stamp identity of the measuring instrument that generated the value The receiver of the data set checks all data for plausibility e Each data set has a unique current identification number which may contain the time when the e Each data set contains information about the origin of the measurement data i e serial number or e In a network with unknown participants authenticity is guaranteed if the data set carries an unambiguous signature The signature covers all of these fields of the data set Additions for Risk Class E Source code of sending and receiving device Required Documentation in addition to the documentation required for risk classes B and C Checks based on the source code Validation Guidance in addit
129. to delete measurement data files if deleting is possible at all e Check that a warning is given if the storage is full or removed Example of an Acceptable Solution e For interruptible measurements that can be stopped easily and rapidly e g weighing fuel measurement etc the measurement may be completed even if the storage becomes unavailable The measuring instrument or the device should have a buffer that is large enough to store the current transaction After this no new transaction may be started and the buffered values are kept for later transmission to a fresh storage e Measurements that are not interruptible e g the measurement of energy volume etc do not need a special intermediate buffer because these measurements always are cumulative The cumulative register can be read out and transmitted to the storage at a later time when the storage is available again e Measurement data may be automatically overwritten by a utility that checks if the measurement data is out of date refer to national regulations for the relevant time period or that the invoice has been paid The utility shall prompt the user for permission to delete and data shall be deleted in the order oldest first Additions for Risk Class E Required Documentation in addition to the documentation required for risk classes B C and D Source code that realises storing of data Validation Guidance in addition to the guidance for risk
130. ts of the software e g measuring instrument application are subject to legal control and may not be inadmissibly modified after approval Parts not subject to legal control may be freely modified f The operating system and low level drivers e g video drivers printer drivers disk drivers etc are not legally relevant unless they are specially programmed for a specific measuring task Table 5 1 Technical description of a Type U measuring instrument 23 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 5 2 Specific Software Requirements for Type U Risk Classes B to E U1 Documentation In addition to the specific documentation required in each requirement below the documentation shall basically include a A description of the legally relevant software functions meaning of the data etc b A description of the accuracy of the measuring algorithms e g price calculation and rounding algorithms A description of the user interface menus and dialogues d A legal software identification e An overview of the system hardware e g topology block diagram type of computer s type of network etc if not described in the operating manual f An overview of the security aspects of the operating system e g protection user accounts privileges etc g The operating manual E Risk Class B Risk Class C Risk Class D U2 Software identification The legally relevant software shall be clearly id
131. x No Denotation Al Annex hes Al 6 Reliability 13 2 Back up Facilities MI 001 7 1 MI 002 3 1 Specific Requirements for Utility 14 2 MI 003 4 3 1 MI 004 4 Meters BD Wake up Facilities and Re Sell 13 3 storih p MI 001 7 1 MI 002 3 1 Specific Requirements for Utility 14 3 g MI 003 4 3 1 MI 004 4 Meters 11 4 12 4 Internal Resolution MI 002 5 8 Mi 068 5 3 SP cme Requirements tor Vullty 13 4 Meters 14 4 11 5 Inhibit resetting of cumulative Al 8 5 Protection against corruption 12 5 measurement values 13 5 14 5 11 6 Indication for the customer Al 7 2 Suitability 12 6 Al 10 5 Indication of result 13 6 14 6 12 7 Acc Sol for monitoring of MI 002 5 2 Specific Requirements for Gas battery lifetime Meters 12 8 Acc Sol for monitoring of MI 002 9 1 Specific Requirements for Gas gas volume converters Meters 12 9 Test element MI 002 5 5 Specific Requirements for Gas Meters l6 1 Fault detection MI 006 IV MI 006 V Discontinuous and continuous Totalisers l6 2 Back up facilities MI 006 IV MI 006 V Discontinuous and continuous Totalisers 13 2 Interpretation of MID Articles and Annexes by MID Software Requirements Software MIP Guide Article Annex No Denotation Comment nn o Al Annex Article Part 1 2 3 No specific software relevance 4 b Definitions Arrange Transmission of legally relevant data T x ment of sub assemblies Basic Guides applicable to sub assemblies P U 5 to 9 No speci
132. ype P or one based on a universal computer Type U Communications links for the download may be direct e g RS 232 USB over a closed network partly or wholly under legal control e g Ethernet token ring LAN or over an open network e g Internet Software Configuration The entire software of the target device may be legally controlled or it may have software separation The download of legally relevant software must follow the requirements outlined below If there is no software separation in the measuring instrument then all of the requirements below apply to all downloads Table 9 1 Technical description of a Type U measuring instrument 55 WELMEC WG7 Software Guide WELMEC 7 2 Issue 1 9 2 Specific Software Requirements Risk Class B Risk Class C Risk Class D D1 Download mechanism Downloading and the subsequent installation of software shall be automatic and shall ensure that the software protection environment is at the approved level on completion Specifying Notes 1 Downloading shall be automatic to ensure that the existing level of protection is not compromised 2 The target device has a fixed legally relevant software that contains all of the checking functions necessary for fulfilling requirements D2 to D5 3 The instrument should be capable of detecting if the download or installation fails A warning shall be given If the download or installation is unsuccessful or is interrupted
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