IEC 62055-41:2014

IEC 62055-41 ®
Edition 2.0 2014-05
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
Electricity metering – Payment systems –
Part 41: Standard transfer specification (STS) – Application layer protocol for
one-way token carrier systems
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form

or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from

either IEC or IEC's member National Committee in the country of the requester. If you have any questions about IEC
copyright or have an enquiry about obtaining additional rights to this publication, please contact the address below or

your local IEC member National Committee for further information.

IEC Central Office Tel.: +41 22 919 02 11
3, rue de Varembé info@iec.ch
CH-1211 Geneva 20 www.iec.ch
Switzerland
About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.

About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigenda or an amendment might have been published.

IEC Catalogue - webstore.iec.ch/catalogue Electropedia - www.electropedia.org
The stand-alone application for consulting the entire The world's leading online dictionary of electronic and
bibliographical information on IEC International Standards, electrical terms containing 21 000 terms and definitions in
Technical Specifications, Technical Reports and other English and French, with equivalent terms in 16 additional
documents. Available for PC, Mac OS, Android Tablets and languages. Also known as the International Electrotechnical
iPad. Vocabulary (IEV) online.

IEC publications search - webstore.iec.ch/advsearchform IEC Glossary - std.iec.ch/glossary
The advanced search enables to find IEC publications by a 67 000 electrotechnical terminology entries in English and
variety of criteria (reference number, text, technical French extracted from the Terms and Definitions clause of
committee,…). It also gives information on projects, replaced IEC publications issued since 2002. Some entries have been
and withdrawn publications. collected from earlier publications of IEC TC 37, 77, 86 and

CISPR.
IEC Just Published - webstore.iec.ch/justpublished
Stay up to date on all new IEC publications. Just Published IEC Customer Service Centre - webstore.iec.ch/csc
details all new publications released. Available online and If you wish to give us your feedback on this publication or
also once a month by email. need further assistance, please contact the Customer Service
Centre: sales@iec.ch.
IEC 62055-41 ®
Edition 2.0 2014-05
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
Electricity metering – Payment systems –

Part 41: Standard transfer specification (STS) – Application layer protocol for

one-way token carrier systems
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 17.220.20; 35.100.70; 91.140.50 ISBN 978-2-8322-1614-9

– 2 – IEC 62055-41:2014 RLV © IEC 2014

CONTENTS
FOREWORD . 8

INTRODUCTION . 2

1 Scope . 13

2 Normative references . 13

3 Terms, definitions and abbreviations . 14

3.1 Terms and definitions. 14

3.2 Abbreviations . 15
3.3 Notation and terminology . 18
4 Numbering conventions . 18
5 Reference model for the standard transfer specification . 19
5.1 Generic payment meter functional reference diagram . 19
5.2 STS protocol reference model . 20
5.3 Dataflow from the POSApplicationProcess to the TokenCarrier . 21
5.4 Dataflow from the TokenCarrier to the MeterApplicationProcess . 22
5.5 MeterFunctionObjects / companion specifications . 23
5.6 ISO transaction reference numbers . 23
6 POSToTokenCarrierInterface application layer protocol . 23
6.1 APDU: ApplicationProtocolDataUnit . 23
6.1.1 Data elements in the APDU . 23
6.1.2 MeterPAN: MeterPrimaryAccountNumber . 25
6.1.3 TCT: TokenCarrierType . 26
6.1.4 DKGA: DecoderKeyGenerationAlgorithm . 27
6.1.5 EA: EncryptionAlgorithm . 27
6.1.6 SGC: SupplyGroupCode . 28
6.1.7 TI: TariffIndex . 28
6.1.8 KRN: KeyRevisionNumber . 29
6.1.9 KT: KeyType . 29
6.1.10 KEN: KeyExpiryNumber . 29
6.1.11 DOE: DateOfExpiry . 29
6.2 Tokens . 30
6.2.1 Token definition format . 30
6.2.2 Class 0: TransferCredit . 30
6.2.3 Class 1: InitiateMeterTest/Display . 31
6.2.4 Class 2: SetMaximumPowerLimit . 31
6.2.5 Class 2: ClearCredit . 31
6.2.6 Class 2: SetTariffRate . 31
6.2.7 Class 2: Set1stSectionDecoderKey . 32
6.2.8 Class 2: Set2ndSectionDecoderKey . 32
6.2.9 Class 2: ClearTamperCondition . 32
6.2.10 Class 2: SetMaximumPhasePowerUnbalanceLimit . 32
6.2.11 Class 2: SetWaterMeterFactor . 32
6.2.12 Class 2: Reserved for STS use . 33
6.2.13 Class 2: Reserved for Proprietary use . 33
6.2.14 Class 3: Reserved for STS use . 33

6.3 Token data elements . 33

6.3.1 Data elements used in tokens . 33

6.3.2 Class: TokenClass . 34

6.3.3 SubClass: TokenSubClass. 34

6.3.4 RND: RandomNumber . 35

6.3.5 TID: TokenIdentifier . 36

6.3.6 Amount: TransferAmount . 37

6.3.7 CRC: CyclicRedundancyCode . 39

6.3.8 Control: InitiateMeterTest/DisplayControlField . 39

6.3.9 MPL: MaximumPowerLimit . 40

6.3.10 MPPUL: MaximumPhasePowerUnbalanceLimit . 40
6.3.11 Rate: TariffRate . 40
6.3.12 WMFactor: WaterMeterFactor . 40
6.3.13 Register: RegisterToClear . 40
6.3.14 NKHO: NewKeyHighOrder . 40
6.3.15 NKLO: NewKeyLowOrder. 40
6.3.16 KENHO: KeyExpiryNumberHighOrder . 40
6.3.17 KENLO: KeyExpiryNumberLowOrder . 41
6.3.18 RO: RolloverKeyChange . 41
6.4 TCDUGeneration functions . 41
6.4.1 Definition of the TCDU . 41
6.4.2 Transposition of the Class bits . 41
6.4.3 TCDUGeneration function for Class 0,1 and 2 tokens . 42
6.4.4 TCDUGeneration function for Set1stSectionDecoderKey token . 42
6.4.5 TCDUGeneration function for Set2ndSectionDecoderKey token . 45
6.5 Security functions . 46
6.5.1 General requirements . 46
6.5.2 Key attributes and key changes . 46
6.5.3 DecoderKey generation . 54
6.5.4 STA: EncryptionAlgorithm07 . 59
6.5.5 DEA: EncryptionAlgorithm09 . 63
7 TokenCarriertoMeterInterface application layer protocol . 63
7.1 APDU: ApplicationProtocolDataUnit . 63
7.1.1 Data elements in the APDU . 63
7.1.2 Token . 64

7.1.3 AuthenticationResult . 64
7.1.4 ValidationResult . 64
7.1.5 TokenResult . 65
7.2 APDUExtraction functions . 66
7.2.1 Extraction process . 66
7.2.2 Extraction of the 2 Class bits . 66
7.2.3 APDUExtraction function for Class 0 and Class 2 tokens . 67
7.2.4 APDUExtraction function for Class 1 tokens . 68
7.2.5 APDUExtraction function for Set1stSectionDecoderKey and
Set2ndSectionDecoderKey tokens . 68

– 4 – IEC 62055-41:2014 RLV © IEC 2014

7.3 Security functions . 69

7.3.1 Key attributes and key changes . 69

7.3.2 DKR: DecoderKeyRegister. 69

7.3.3 STA: DecryptionAlgorithm07 . 70

7.3.4 DEA: DecryptionAlgorithm09 . 72

7.3.5 TokenAuthentication . 73

7.3.6 TokenValidation . 74

7.3.7 TokenCancellation . 74

8 MeterApplicationProcess requirements . 75

8.1 General requirements . 75
8.2 Token acceptance/rejection . 75
8.3 Display indicators and markings . 76
8.4 TransferCredit tokens . 77
8.5 InitiateMeterTest/Display tokens . 77
8.6 SetMaximumPowerLimit tokens. 77
8.7 ClearCredit tokens . 78
8.8 SetTariffRate tokens . 78
8.9 Set1stSectionDecoderKey tokens . 78
8.10 Set2ndSectionDecoderKey tokens . 78
8.11 ClearTamperCondition tokens . 78
8.12 SetMaximumPhasePowerUnbalanceLimit tokens . 79
8.13 SetWaterMeterFactor . 79
8.14 Class 2: Reserved for STS use tokens . 79
8.15 Class 2: Reserved for Proprietary use tokens . 79
8.16 Class 3: Reserved for STS use tokens . 79
9 KMS: KeyManagementSystem generic requirements . 79
10 Maintenance of STS entities and related services . 80
10.1 General . 80
10.2 Operations . 82
10.2.1 Product certification maintenance . 82
10.2.2 DSN maintenance . 82
10.2.3 RO maintenance . 82
10.2.4 TI maintenance . 82
10.2.5 TID maintenance . 83
10.2.6 SpecialReservedTokenIdentifier maintenance . 83

10.2.7 MfrCode maintenance . 83
10.2.8 Substitution tables maintenance . 83
10.2.9 Permutation tables maintenance . 83
10.2.10 SGC maintenance . 83
10.2.11 VendingKey maintenance . 83
10.2.12 KRN maintenance . 83
10.2.13 KT maintenance . 83
10.2.14 KEN maintenance . 84
10.2.15 KEK maintenance . 84
10.2.16 CC maintenance . 84
10.2.17 UC maintenance . 84
10.2.18 KMCID maintenance . 84
10.2.19 CMID maintenance . 84
10.2.20 CMAC maintenance . 84

10.3 Standardisation . 85

10.3.1 IIN maintenance . 85

10.3.2 TCT maintenance . 85

10.3.3 DKGA maintenance . 85

10.3.4 EA maintenance . 85

10.3.5 TokenClass maintenance . 85

10.3.6 TokenSubClass maintenance. 85

10.3.7 InitiateMeterTest/DisplayControlField maintenance. 86

10.3.8 RegisterToClear maintenance . 86

10.3.9 STS base date maintenance . 86

10.3.10 Rate maintenance. 86
10.3.11 WMFactor maintenance . 86
10.3.12 MFO maintenance . 87
10.3.13 FOIN maintenance . 87
10.3.14 Companion specification maintenance . 87
Annex A (informative) Guidelines for a KeyManagementSystem (KMS) . 88
Annex B (informative) Entities and identifiers in an STS-compliant system . 91
Annex C (informative) Code of practice for the implementation of STS-compliant
systems . 95
C.1 Maintenance and support services provided by the STS Association . 95
C.2 Key management . 95
C.2.1 Key management services . 95
C.2.2 SupplyGroupCode and VendingKey distribution . 95
C.2.3 CryptographicModule distribution . 96
C.2.4 Key expiry . 97
C.3 MeterPAN . 97
C.3.1 General practice . 97
C.3.2 IssuerIdentificationNumbers . 97
C.3.3 ManufacturerCodes . 97
C.3.4 DecoderSerialNumbers . 98
C.4 SpecialReservedTokenIdentifier . 98
C.5 Permutation and substitution tables for the STA . 99
C.6 EA codes . 99
C.7 TokenCarrierType codes . 99
C.8 MeterFunctionObject instances / companion specifications . 99

C.9 TariffIndex . 99
C.10 STS-compliance certification . 100
C.10.1 IEC certification services . 100
C.10.2 Products . 100
C.10.3 Certification authority . 100
C.11 Procurement options for users of STS-compliant systems . 100
C.12 Management of TID Rollover . 104
C.12.1 Introduction . 104
C.12.2 Overview . 105
C.12.3 Impact analysis . 107
C.12.4 Base dates . 108
C.12.5 Implementation . 108
Bibliography . 110

– 6 – IEC 62055-41:2014 RLV © IEC 2014

Figure 1 – Functional block diagram of a generic single-part payment meter . 19

Figure 2 – STS modelled as a 2-layer collapsed OSI protocol stack . 20

Figure 3 – Dataflow from the POSApplicationProcess to the TokenCarrier . 21

Figure 4 – Dataflow from the TokenCarrier to the MeterApplicationProcess . 22

Figure 5 – Composition of ISO transaction reference number . 23

Figure 6 – Transposition of the 2 Class bits . 41

Figure 7 – TCDUGeneration function for Class 0, 1 and 2 tokens . 42

Figure 8 – TCDUGeneration function for Set1stSectionDecoderKey token . 43

Figure 9 – TCDUGeneration function for Set2ndSectionDecoderKey token . 45
Figure 10 – DecoderKey changes – state diagram . 51
Figure 11 – DecoderKeyGenerationAlgorithm01 . 56
Figure 12 – DecoderKeyGenerationAlgorithm02 . 57
Figure 13 – DecoderKeyGenerationAlgorithm03 . 58
Figure 14 – STA: EncryptionAlgorithm07. 59
Figure 15 – STA encryption substitution process. 60
Figure 16 – STA encryption permutation process . 61
Figure 17 – STA encryption DecoderKey rotation process . 61
Figure 18 – STA encryption worked example for TransferCredit token . 62
Figure 19 – DEA: EncryptionAlgorithm09 . 63
Figure 20 – APDUExtraction function . 66
Figure 21 – Extraction of the 2 Class bits . 67
Figure 22 – STA DecryptionAlgorithm07 . 70
Figure 23 – STA decryption permutation process . 70
Figure 24 – STA decryption substitution process. 71
Figure 25 – STA decryption DecoderKey rotation process . 72
Figure 26 – STA decryption worked example for TransferCredit token . 72
Figure 27 – DEA DecryptionAlgorithm09 . 73
Figure A.1 – KeyManagementSystem and interactive relationships between entities . 88
Figure B.1 – Entities and identifiers deployed in an STS-compliant system . 91
Figure C.1 – System overview . 106

Table 1 – Data elements in the APDU . 24
Table 2 – Data elements in the IDRecord . 24
Table 3 – Data elements in the MeterPAN . 25
Table 4 – Data elements in the IAIN / DRN . 26
Table 5 – Token carrier types . 27
Table 6 – DKGA codes . 27
Table 7 – EA codes. 28
Table 8 – SGC types and key types . 28
Table 9 – DOE codes for the year . 30
Table 10 – DOE codes for the month . 30
Table 11 –Token definition format . 30
Table 12 – Data elements used in tokens. 33

Table 13 – Token classes . 34

Table 14 – Token sub-classes . 35

Table 15 – TID calculation examples . 36

Table 16 – Units of measure for electricity . 37

Table 17 – Units of measure for other applications . 37

Table 18 – Bit allocations for the TransferAmount . 38

Table 19 – Maximum error due to rounding . 38

Table 20 – Examples of TransferAmount values for credit transfer . 38

Table 21 – Example of a CRC calculation . 39
Table 22 – Permissible control field values . 39
Table 23 – Selection of register to clear . 40
Table 24 – Classification of vending keys . 47
Table 25 – Classification of decoder keys . 48
Table 26 – Permitted relationships between decoder key types . 52
Table 27 – Definition of the PANBlock . 54
Table 28 – Data elements in the PANBlock . 54
Table 29 – Definition of the CONTROLBlock . 55
Table 30 – Data elements in the CONTROLBlock . 55
Table 31 – Range of applicable decoder reference numbers . 55
Table 32 – List of applicable supply group codes . 56
Table 33 – Sample substitution tables . 60
Table 34 – Sample permutation table . 61
Table 35 – Data elements in the APDU . 64
Table 36 – Possible values for the AuthenticationResult . 64
Table 37 – Possible values for the ValidationResult . 65
Table 38 – Possible values for the TokenResult . 65
Table 39 – Values stored in the DKR . 69
Table 40 – Sample permutation table . 70
Table 41 – Sample substitution tables . 71
Table 42 – Entities/services requiring maintenance service . 81
Table A.1 – Entities that participate in KMS processes . 88

Table A.2 – Processes surrounding the payment meter and DecoderKey . 89
Table A. 3 – Processes surrounding the CryptographicModule . 89
Table A.4 – Processes surrounding the SGC and VendingKey . 90
Table B.1 – Typical entities deployed in an STS-compliant system . 92
Table B.2 – Identifiers associated with the entities in an STS-compliant system . 93
Table C.1 – Data elements associated with a SGC . 96
Table C.2 – Data elements associated with the CryptographicModule . 97
Table C.3 – Items that should be noted in purchase orders and tenders . 100

– 8 – IEC 62055-41:2014 RLV © IEC 2014

INTERNATIONAL ELECTROTECHNICAL COMMISSION

____________
ELECTRICITY METERING – PAYMENT SYSTEMS –

Part 41: Standard transfer specification (STS) –

Application layer protocol for one-way token carrier systems

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.

This redline version of the official IEC Standard allows the user to identify the changes
made to the previous edition. A vertical bar appears in the margin wherever a change
has been made. Additions are in green text, deletions are in strikethrough red text.

International Standard IEC 62055-41 has been prepared by IEC technical committee 13:

Electrical energy measurement and control.

This second edition cancels and replaces the first edition issued in 2007. It constitutes a

technical revision. The main technical changes with regard to the previous edition are as

follows:
• Class 2 token is extended to include credit transfer for gas and water with associated

extensions in the display/test tokens.

• MfrCode is extended from 2 to 4 digits.

• Three token identifier base dates are defined to provide for more frequent key changes

with TID roll-over procedures.
• A code of practice for the management of TID roll-over key changes in association with
the revised set of base dates.
• Some clarifications and additional examples have been added.
The text of this standard is based on the following documents:
CDV Report on voting
13/1530/CDV 13/1553/RVC
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
A list of all parts in the IEC 62055 series, published under the general title Electricity metering
– Payment systems, can be found on the IEC website.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
The committee has decided that the contents of this publication will remain unchanged until
the stability date indicated on the IEC web site under "http://webstore.iec.ch" in the data
related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
– 10 – IEC 62055-41:2014 RLV © IEC 2014

INTRODUCTION
The IEC 62055 series covers payment systems, encompassing the customer information

systems, point of sale systems, token carriers, payment meters and the respective interfaces

that exist between these entities. At the time of preparation of this standard, IEC 62055

comprised the following parts, under the general title, Electricity metering – Payment systems:

Part 21: Framework for standardization

Part 31: Particular requirements – Static payment meters for active energy (classes 1 and 2)

Part 41: Standard transfer specification – Application layer protocol for one-way token

carrier systems
Part 51: Standard transfer specification – Physical layer protocol for one-way numeric and
magnetic card token carriers
Part 52: Standard transfer specification – Physical layer protocol for a two-way virtual token
carrier for direct local connection
Part 4x series specify application layer protocols and Part 5x series specify physical layer
protocols.
The standard transfer specification (STS) is a secure message protocol that allows
information to be carried between point of sale (POS) equipment and payment meters and it
caters for several message types such as credit, configuration control, display and test
instructions. It further specifies devices and codes of practice that allow for the secure
management (generation, storage, retrieval and transportation) of cryptographic keys used
within the system.
The national electricity utility in South Africa (Eskom) first developed and published the STS
in 1993 and transferred ownership to the STS Association in 1998 for management and
further development. It is currently the only open system for one-way payment meters and to
date there are more than 4 million STS payment meters in the field, being used by
approximately 400 utilities in 28 countries. The STS has been stable for 10 years, is the de
facto industry standard at national and international level and hence has been developed as
an IEC standard with the appropriate reformatting to comply with WG15 work. The primary
application of the STS has been for use with payment meters without a tariff employing
energy-based tokens, but it could be applied to currency-based token systems.
Prior to the development of the STS a variety of proprietary payment meters and POS
equipment had been developed, which were, however, not compatible with each other. This
gave rise to a definite need among the major users to move towards standardized solutions in
addressing operational problems experienced where various types of payment meter and POS
equipment had to be operated simultaneously. A standard transfer specification was

developed that would allow for the application and inter-operability of payment meters and
POS equipment from multiple manufacturers in a payment metering installation.
Two encryption algorithms are in this standard. The STA is used in existing systems, while
the DEA may be considered for future systems.
The token carrier, which is not specified in this part of IEC 62055, is the physical device or
medium used to transport the information from the POS equipment to the payment meter.
Three types of token carriers are currently specified in IEC 62055-51 and IEC 62055-52; the
magnetic card, the numeric token carrier and a virtual token carrier, which have been
approved by the STS Association. New token carriers can be proposed as new work items
through the National Committees or through the STS Association.

Although the main implementation of the STS is in the electricity supply industry, it inherently

provides for the management of other utility services such as water and gas. It should be

noted that certain functionalities may not apply across all utility services, for example,

MaximumPowerLimit in the case of a water meter. Similarly, certain terminology may not be

appropriate
...