ISO IEC 8825-1-2015 Information technology - ASN 1 encoding rules Specification of Basic Encoding Rules (BER) Canonical Encoding Rules (CER) and Distinguished E.pdf

1、 Reference number ISO/IEC 8825-1:2015(E) ISO/IEC 2015INTERNATIONAL STANDARD ISO/IEC 8825-1 Fifth edition 2015-11-15 Information technology ASN.1 encoding rules: Specification of Basic Encoding Rules (BER), Canonical Encoding Rules (CER) and Distinguished Encoding Rules (DER) Technologies de linforma

2、tion Rgles de codage ASN.1: Spcification des rgles de codage de base (BER), des rgles de codage canoniques (CER) et des rgles de codage distinctives (DER) ISO/IEC 8825-1:2015(E) COPYRIGHT PROTECTED DOCUMENT ISO/IEC 2015 All rights reserved. Unless otherwise specified, no part of this publication may

3、 be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below or ISOs member body in the country of the

4、requester. ISO copyright office Case postale 56 CH-1211 Geneva 20 Tel. + 41 22 749 01 11 Fax + 41 22 749 09 47 E-mail copyrightiso.org Web www.iso.org Published in Switzerland ii ISO/IEC 2015 All rights reservedISO/IEC 8825-1:2015(E) ISO/IEC 2015 All rights reserved iiiForeword ISO (the Internationa

5、l Organization for Standardization) and IEC (the International Electrotechnical Commission) form the specialized system for worldwide standardization. National bodies that are members of ISO or IEC participate in the development of International Standards through technical committees established by

6、the respective organization to deal with particular fields of technical activity. ISO and IEC technical committees collaborate in fields of mutual interest. Other international organizations, governmental and non-governmental, in liaison with ISO and IEC, also take part in the work. In the field of

7、information technology, ISO and IEC have established a joint technical committee, ISO/IEC JTC 1. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The main task of the joint technical committee is to prepare International Standards. Draft Inter

8、national Standards adopted by the joint technical committee are circulated to national bodies for voting. Publication as an International Standard requires approval by at least 75 % of the national bodies casting a vote. Attention is drawn to the possibility that some of the elements of this documen

9、t may be the subject of patent rights. ISO and IEC shall not be held responsible for identifying any or all such patent rights. This fifth edition cancels and replaces the fourth edition of ISO/IEC 8825-1:2008 which has been technically revised. It also incorporates ISO/IEC 8825-1:2008/Cor.1:2012 an

10、d ISO/IEC 8825-5:2008.Cor.2:2014. ISO/IEC 8825-1 was prepared by Joint Technical Committee ISO/IEC JTC 1, Information technology, Subcommittee SC 6, Telecommunications and information exchange between systems, in collaboration with ITU-T. The identical text is published as ITU-T X.690 (08/2015). I n

11、 t e r n a t i o n a l T e l e c o m m u n i c a t i o n U n i o n ITU-T X.690 TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (08/2015) SERIES X: DATA NETWORKS, OPEN SYSTEM COMMUNICATIONS AND SECURITY OSI networking and system aspects Abstract Syntax Notation One (ASN.1) Information technology ASN.

12、1 encoding rules: Specification of Basic Encoding Rules (BER), Canonical Encoding Rules (CER) and Distinguished Encoding Rules (DER) Recommendation ITU-T X.690 ITU-T X-SERIES RECOMMENDATIONS DATA NETWORKS, OPEN SYSTEM COMMUNICATIONS AND SECURITY PUBLIC DATA NETWORKS Services and facilities X.1X.19 I

13、nterfaces X.20X.49 Transmission, signalling and switching X.50X.89 Network aspects X.90X.149 Maintenance X.150X.179 Administrative arrangements X.180X.199 OPEN SYSTEMS INTERCONNECTION Model and notation X.200X.209 Service definitions X.210X.219 Connection-mode protocol specifications X.220X.229 Conn

14、ectionless-mode protocol specifications X.230X.239 PICS proformas X.240X.259 Protocol Identification X.260X.269 Security Protocols X.270X.279 Layer Managed Objects X.280X.289 Conformance testing X.290X.299 INTERWORKING BETWEEN NETWORKS General X.300X.349 Satellite data transmission systems X.350X.36

15、9 IP-based networks X.370X.379 MESSAGE HANDLING SYSTEMS X.400X.499 DIRECTORY X.500X.599 OSI NETWORKING AND SYSTEM ASPECTS Networking X.600X.629 Efficiency X.630X.639 Quality of service X.640X.649 Naming, Addressing and Registration X.650X.679 Abstract Syntax Notation One (ASN.1) X.680X.699 OSI MANAG

16、EMENT Systems management framework and architecture X.700X.709 Management communication service and protocol X.710X.719 Structure of management information X.720X.729 Management functions and ODMA functions X.730X.799 SECURITY X.800X.849 OSI APPLICATIONS Commitment, concurrency and recovery X.850X.8

17、59 Transaction processing X.860X.879 Remote operations X.880X.889 Generic applications of ASN.1 X.890X.899 OPEN DISTRIBUTED PROCESSING X.900X.999 INFORMATION AND NETWORK SECURITY X.1000X.1099 SECURE APPLICATIONS AND SERVICES X.1100X.1199 CYBERSPACE SECURITY X.1200X.1299 SECURE APPLICATIONS AND SERVI

18、CES X.1300X.1399 CYBERSECURITY INFORMATION EXCHANGE X.1500X.1599 CLOUD COMPUTING SECURITY X.1600X.1699 For further details, please refer to the list of ITU-T Recommendations. Rec. ITU-T X.690 (08/2015) i INTERNATIONAL STANDARD ISO/IEC 8825-1 RECOMMENDATION ITU-T X.690 Information technology ASN.1 en

19、coding rules: Specification of Basic Encoding Rules (BER), Canonical Encoding Rules (CER) and Distinguished Encoding Rules (DER) Summary Recommendation ITU-T X.690 | ISO/IEC 8825-1 defines a set of Basic Encoding Rules (BER) that may be applied to values of types defined using the ASN.1 notation. Ap

20、plication of these encoding rules produces a transfer syntax for such values. It is implicit in the specification of these encoding rules that they are also used for decoding. This Recommendation | International Standard defines also a set of Distinguished Encoding Rules (DER) and a set of Canonical

21、 Encoding Rules (CER) both of which provide constraints on the Basic Encoding Rules (BER). The key difference between them is that DER uses the definite length form of encoding while CER uses the indefinite length form. DER is more suitable for the small encoded values, while CER is more suitable fo

22、r the large ones. It is implicit in the specification of these encoding rules that they are also used for decoding. History Edition Recommendation Approval Study Group Unique ID *1.0 ITU-T X.690 1994-07-01 7 11.1002/1000/3046 1.1 ITU-T X.690 (1994) Technical Cor. 1 1995-11-21 7 11.1002/1000/3283 1.2

23、 ITU-T X.690 (1994) Technical Cor. 2 1997-12-12 7 11.1002/1000/4182 1.3 ITU-T X.690 (1994) Technical Cor. 3 1997-12-12 7 11.1002/1000/4183 2.0 ITU-T X.690 1997-12-12 7 11.1002/1000/4447 2.1 ITU-T X.690 (1997) Technical Cor. 1 1999-06-18 7 11.1002/1000/4705 2.2 ITU-T X.690 (1997) Amd. 1 1999-06-18 7

24、11.1002/1000/4704 2.3 ITU-T X.690 (1997) Technical Cor. 2 2001-02-02 7 11.1002/1000/5335 3.0 ITU-T X.690 2002-07-14 17 11.1002/1000/6089 3.1 ITU-T X.690 (2002) Amd. 1 2003-10-29 17 11.1002/1000/7021 3.2 ITU-T X.690 (2002) Amd. 2 2006-06-13 17 11.1002/1000/8838 3.3 ITU-T X.690 (2002) Technical Cor. 1

25、 2007-05-29 17 11.1002/1000/9108 4.0 ITU-T X.690 2008-11-13 17 11.1002/1000/9608 4.1 ITU-T X.690 (2008) Cor. 1 2011-10-14 17 11.1002/1000/11378 4.2 ITU-T X.690 (2008) Cor. 2 2014-03-01 17 11.1002/1000/12147 5.0 ITU-T X.690 2015-08-13 17 11.1002/1000/12483 *To access the Recommendation, type the URL

26、http:/handle.itu.int/ in the address field of your web browser, followed by the Recommendations unique ID. For example, http:/handle.itu.int/11.1002/1000/11830-en. ii Rec. ITU-T X.690 (11/2015) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the f

27、ield of telecommunications, information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standard

28、izing telecommunications on a worldwide basis. The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics. The approval of ITU-T Recommendations is cover

29、ed by the procedure laid down in WTSA Resolution 1. In some areas of information technology which fall within ITU-Ts purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. NOTE In this Recommendation, the expression “Administration“ is used for conciseness to indica

30、te both a telecommunication administration and a recognized operating agency. Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure, e.g., interoperability or applicability) and compliance with the Recommendation is achieved

31、 when all of these mandatory provisions are met. The words “shall“ or some other obligatory language such as “must“ and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party. INTELLECTUAL PRO

32、PERTY RIGHTS ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asser

33、ted by ITU members or others outside of the Recommendation development process. As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementers are cautioned t

34、hat this may not represent the latest information and are therefore strongly urged to consult the TSB patent database at http:/www.itu.int/ITU-T/ipr/. ITU 2015 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. Re

35、c. ITU-T X.690 (08/2015) iii CONTENTS Page Introduction . v 1 Scope 1 2 Normative references 1 2.1 Identical Recommendations | International Standards 1 2.2 Additional references 1 3 Definitions 1 4 Abbreviations . 2 5 Notation 2 6 Convention . 2 7 Conformance 3 8 Basic encoding rules . 3 8.1 Genera

36、l rules for encoding 3 8.2 Encoding of a boolean value . 6 8.3 Encoding of an integer value . 6 8.4 Encoding of an enumerated value . 7 8.5 Encoding of a real value 7 8.6 Encoding of a bitstring value. 8 8.7 Encoding of an octetstring value . 9 8.8 Encoding of a null value 10 8.9 Encoding of a seque

37、nce value . 10 8.10 Encoding of a sequence-of value. 10 8.11 Encoding of a set value . 10 8.12 Encoding of a set-of value . 11 8.13 Encoding of a choice value . 11 8.14 Encoding of a value of a prefixed type 11 8.15 Encoding of an open type 12 8.16 Encoding of an instance-of value 12 8.17 Encoding o

38、f a value of the embedded-pdv type 12 8.18 Encoding of a value of the external type . 12 8.19 Encoding of an object identifier value. 13 8.20 Encoding of a relative object identifier value 14 8.21 Encoding of an OID internationalized resource identifier value . 14 8.22 Encoding of a relative OID int

39、ernationalized resource identifier value 15 8.23 Encoding for values of the restricted character string types 15 8.24 Encoding for values of the unrestricted character string type . 17 8.25 Encoding for values of the useful types 17 8.26 Encoding for values of the TIME type and the useful time types

40、 17 9 Canonical encoding rules . 17 9.1 Length forms . 18 9.2 String encoding forms . 18 9.3 Set components . 18 10 Distinguished encoding rules 18 10.1 Length forms . 18 10.2 String encoding forms . 18 10.3 Set components . 19 11 Restrictions on BER employed by both CER and DER . 19 11.1 Boolean va

41、lues 19 11.2 Unused bits 19 11.3 Real values 19 iv Rec. ITU-T X.690 (11/2015) 11.4 GeneralString values . 19 11.5 Set and sequence components with default value . 20 11.6 Set-of components . 20 11.7 GeneralizedTime . 20 11.8 UTCTime 20 11.9 The TIME type and the useful time types 21 12 Use of BER, C

42、ER and DER in transfer syntax definition 21 Annex A Example of encodings . 23 A.1 ASN.1 description of the record structure . 23 A.2 ASN.1 description of a record value . 23 A.3 Representation of this record value . 23 Annex B Identification of Encoding Rules . 25 Annex C Illustration of real value

43、encoding . 26 Rec. ITU-T X.690 (08/2015) v Introduction Rec. ITU-T X.680 | ISO/IEC 8824-1, Rec. ITU-T X.681 | ISO/IEC 8824-2, Rec. ITU-T X.682 | ISO/IEC 8824-3, Rec. ITU-T X.683 | ISO/IEC 8824-4 (Abstract Syntax Notation One or ASN.1) together specify a notation for the definition of abstract syntax

44、es, enabling application standards to define the types of information they need to transfer. It also specifies a notation for the specification of values of a defined type. This Recommendation | International Standard defines encoding rules that may be applied to values of types defined using the AS

45、N.1 notation. Application of these encoding rules produces a transfer syntax for such values. It is implicit in the specification of these encoding rules that they are also to be used for decoding. There may be more than one set of encoding rules that can be applied to values of types that are defin

46、ed using the ASN.1 notation. This Recommendation | International Standard defines three sets of encoding rules, called basic encoding rules, canonical encoding rules and distinguished encoding rules. Whereas the basic encoding rules give the sender of an encoding various choices as to how data value

47、s may be encoded, the canonical and distinguished encoding rules select just one encoding from those allowed by the basic encoding rules, eliminating all of the senders options. The canonical and distinguished encoding rules differ from each other in the set of restrictions that they place on the ba

48、sic encoding rules. The distinguished encoding rules is more suitable than the canonical encoding rules if the encoded value is small enough to fit into the available memory and there is a need to rapidly skip over some nested values. The canonical encoding rules is more suitable than the distinguis

49、hed encoding rules if there is a need to encode values that are so large that they cannot readily fit into the available memory or it is necessary to encode and transmit a part of a value before the entire value is available. The basic encoding rules is more suitable than the canonical or distinguished encoding rules if the encoding contains a set value or set-of value and there is no need for the restrictions that the canonical and distinguished encoding rules impose. This is due to the memory and CPU over