ISO/IEC DIS 8825-8

Information technology -- ASN.1 encoding rules

Technologies de l'information -- Règles de codage ASN.1

Standards Content (sample)

DRAFT INTERNATIONAL STANDARD
ISO/IEC DIS 8825-8
ISO/IEC JTC 1/SC 6 Secretariat: KATS
Voting begins on: Voting terminates on:
2020-09-28 2020-12-21
Information technology — ASN.1 encoding rules —
Part 8:
Specification of JavaScript Object Notation Encoding
Rules (JER)
ICS: 35.100.60
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENT AND APPROVAL. IT IS
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NATIONAL REGULATIONS.
ISO/IEC DIS 8825-8:2020(E)
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ISO/IEC DIS 8825-8:2020(E)
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ISO/IEC DIS 8825-8:2020(E)
CONTENTS
Page

1 Scope ................................................................................................................................................................ 1

2 Normative references ......................................................................................................................................... 1

2.1 Identical Recommendations | International Standards ............................................................................. 1

2.2 Additional references ............................................................................................................................... 1

3 Definitions .......................................................................................................................................................... 2

3.1 Specification of Basic Notation ............................................................................................................... 2

3.2 Information Object Specification ............................................................................................................. 2

3.3 Constraint Specification ........................................................................................................................... 2

3.4 Parameterization of ASN.1 Specification ................................................................................................ 2

3.5 Basic Encoding Rules (BER) ................................................................................................................... 2

3.6 Packed Encoding Rules (PER) ................................................................................................................. 2

3.7 Additional definitions .............................................................................................................................. 2

4 Abbreviations ..................................................................................................................................................... 3

5 Encodings specified by this Recommendation | International Standard ............................................................. 3

6 Conformance ...................................................................................................................................................... 4

7 General provisions ............................................................................................................................................. 4

7.1 Use of the type notation ........................................................................................................................... 4

7.2 Constraints ............................................................................................................................................... 4

7.3 Type and value model used for encoding ................................................................................................. 6

7.4 Types to be encoded ................................................................................................................................. 6

7.5 Encoding instructions ............................................................................................................................... 6

7.6 Production of a complete JER encoding .................................................................................................. 7

8 Notation, lexical items and keywords used in JER encoding instructions ......................................................... 7

9 Specifying JER encoding instructions ................................................................................................................ 8

10 Assigning a JER encoding instruction using a type prefix ................................................................................. 9

11 Assigning a JER encoding instruction using a JER encoding control section .................................................... 9

12 Identification of the targets for a JER encoding instruction ............................................................................... 9

12.1 General rules ............................................................................................................................................ 9

12.2 Types defined in the module .................................................................................................................... 10

12.3 Built-in types ............................................................................................................................................ 10

12.4 Types imported from another module ...................................................................................................... 10

13 Multiple assignment of JER encoding instructions ............................................................................................ 10

13.1 Order in which multiple assignments are considered ............................................................................... 10

13.2 Effect of assigning a negating encoding instruction................................................................................. 11

13.3 Multiple assignment of JER encoding instructions of the same category ................................................ 11

14 The ARRAY encoding instruction ....................................................................................................................... 11

14.1 General .................................................................................................................................................. 11

ii Rec. ITU-T X.697 (10/2017)
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14.2 Restrictions .............................................................................................................................................. 11

15 The BASE64 encoding instruction ..................................................................................................................... 11

15.1 General .................................................................................................................................................. 11

15.2 Restrictions .............................................................................................................................................. 12

16 The NAME encoding instruction.......................................................................................................................... 12

16.1 General .................................................................................................................................................. 12

16.2 Restrictions .............................................................................................................................................. 13

17 The OBJECT encoding instruction ..................................................................................................................... 13

17.1 General .................................................................................................................................................. 13

17.2 Restrictions .............................................................................................................................................. 13

18 The TEXT encoding instruction.......................................................................................................................... 13

18.1 General .................................................................................................................................................. 13

18.2 Restrictions .............................................................................................................................................. 14

19 The UNWRAPPED encoding instruction .............................................................................................................. 14

19.1 General .................................................................................................................................................. 14

19.2 Restrictions .............................................................................................................................................. 14

20 Encoding of boolean values ............................................................................................................................... 14

21 Encoding of integer values ................................................................................................................................. 15

22 Encoding of enumerated values ......................................................................................................................... 15

23 Encoding of real values ...................................................................................................................................... 15

23.1 General .................................................................................................................................................. 15

23.2 Encoding of the special real values .......................................................................................................... 15

23.3 Encoding as a JSON number .................................................................................................................... 16

23.4 Encoding as a JSON object ...................................................................................................................... 16

24 Encoding of bitstring values ............................................................................................................................... 16

24.1 General .................................................................................................................................................. 16

24.2 Encoding of bitstring types with a fixed size ........................................................................................... 16

24.3 Encoding of bitstring types with a variable size ....................................................................................... 16

25 Encoding of octetstring values ........................................................................................................................... 16

26 Encoding of the null value ................................................................................................................................. 17

27 Encoding of sequence values ............................................................................................................................. 17

27.1 General .................................................................................................................................................. 17

27.2 Array-based encoding .............................................................................................................................. 17

27.3 Object-based encoding ............................................................................................................................. 17

28 Encoding of sequence-of values ......................................................................................................................... 17

29 Encoding of set values........................................................................................................................................ 18

30 Encoding of set-of values ................................................................................................................................... 18

Rec. ITU-T X.697 (10/2017) iii
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30.1 General .................................................................................................................................................. 18

30.2 Array-based encoding .............................................................................................................................. 18

30.3 Object-based encoding ............................................................................................................................. 18

31 Encoding of choice values .................................................................................................................................. 18

31.1 General .................................................................................................................................................. 18

31.2 Unwrapped encoding ............................................................................................................................... 18

31.3 Wrapped encoding ................................................................................................................................... 18

32 Encoding of object identifier values ................................................................................................................... 19

33 Encoding of relative object identifier values ...................................................................................................... 19

34 Encoding of values of the internationalized resource reference type ................................................................. 19

35 Encoding of values of the relative internationalized resource reference type .................................................... 19

36 Encoding of values of the embedded-pdv type .................................................................................................. 19

37 Encoding of values of the external type ............................................................................................................. 19

38 Encoding of values of the restricted character string types ................................................................................ 19

39 Encoding of values of the unrestricted character string type .............................................................................. 20

40 Encoding of values of the time types ................................................................................................................. 20

41 Encoding of open type values ............................................................................................................................ 20

Annex A – Examples of JER encodings .......................................................................................................................... 21

A.1 ASN.1 description of the record structure ................................................................................................ 21

A.2 ASN.1 description of a record value ........................................................................................................ 21

A.3 Example JER representation of this record value..................................................................................... 21

A.4 Additional examples of JER encodings ................................................................................................... 22

Annex B – Examples of JER encoding instructions and their effect on the encodings ................................................... 25

B.1 ASN.1 description of the record structure ................................................................................................ 25

B.2 ASN.1 description of a record value ........................................................................................................ 25

B.3 JER representation of this record value .................................................................................................... 26

B.4 Additional examples of JER encodings ................................................................................................... 26

B.5 Examples of JER encodings of choice types ............................................................................................ 28

iv Rec. ITU-T X.697 (10/2017)
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ISO/IEC DIS 8825-8:2020(E)
Introduction

The publications 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 together describe Abstract Syntax Notation One (ASN.1), a

notation for the definition of messages to be exchanged between peer applications.

This Recommendation |International Standard defines encoding rules that may be applied to values of ASN.1 types

defined using the notation specified in the above-mentioned publications. 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 are more than one set of encoding rules that can be applied to values of ASN.1 types. This Recommendation |

International Standard defines a set of JavaScript Object Notation Encoding Rules (JER), so called because the

encodings they produce are instances of the JSON grammar specified in ECMA 404.

This Recommendation | International Standard specifies the syntax and semantics of JER encoding instructions which

modify the JSON text produced by the application of JER to certain ASN.1 types.

Clauses 8 to 12 list the JER encoding instructions and specify the syntax for their assignment to an ASN.1 type or

component using either a JER type prefix (see Rec. ITU-T X.680 | ISO/IEC 8824-1, clause 31.3) or a JER encoding

control section (see Rec. ITU-T X.680 | ISO/IEC 8824-1, clause 54).

Clause 13 defines the order of precedence if JER encoding instructions are present in both a JER type prefix and in a

JER encoding control section.
Clauses 14 to 19 specify:

a) the syntax of each JER encoding instruction used in a type prefix or a JER encoding control section;

b) restrictions on the JER encoding instructions that can be associated with a particular ASN.1 type

(resulting from inheritance and multiple assignments).

Clauses 20 to 41 specify the JER encoding of ASN.1 types, referencing earlier clauses which define the JER encoding

instructions.

Annex A is informative and contains examples of JER encodings where JER encoding instructions are not used.

Annex B is informative and contains examples of JER encoding instructions and their effect on the JER encodings.

Rec. ITU-T X.697 (10/2017) v
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ISO/IEC DIS 8825-8:2020(E)
ISO/IEC 8825-8:2018 (E)
INTERNATIONAL STANDARD
ITU-T RECOMMENDATION
Information technology – ASN.1 encoding rules: Specification of JavaScript
Object Notation Encoding Rules (JER)
1 Scope

This Recommendation | International Standard specifies a set of JavaScript Object Notation Encoding Rules (JER) that

may be used to derive a transfer syntax for values of types defined in 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. It is implicit in the

specification of these encoding rules that they are also to be used for decoding.

The encoding rules specified in this Recommendation | International Standard:
– are used at the time of communication;

– are intended for use in circumstances where interoperability with applications using JSON is the major

concern in the choice of encoding rules;

– allow the extension of an abstract syntax by addition of extra values for all forms of extensibility

described in Rec. ITU-T X.680 | ISO/IEC 8824-1.

This Recommendation | International Standard also specifies the syntax and semantics of JER encoding instructions,

and the rules for their assignment and combination. JER encoding instructions can be used to control the JER encoding

for specific ASN.1 types.
2 Normative references

The following Recommendations and International Standards contain provisions which, through reference in this text,

constitute provisions of this Recommendation | International Standard. At the time of publication, the editions indicated

were valid. All Recommendations and Standards are subject to revision, and parties to agreements based on this

Recommendation | International Standard are encouraged to investigate the possibility of applying the most recent

edition of the Recommendations and Standards listed below. Members of IEC and ISO maintain registers of currently

valid International Standards. The Telecommunication Standardization Bureau of the ITU maintains a list of currently

valid ITU-T Recommendations.
2.1 Identical Recommendations | International Standards

– Recommendation ITU-T X.680 (2020) | ISO/IEC 8824-1:2020, Information technology – Abstract

Syntax Notation One (ASN.1): Specification of basic notation.

– Recommendation ITU-T X.681 (2020) | ISO/IEC 8824-2:2020, Information technology – Abstract

Syntax Notation One (ASN.1): Information object specification.

– Recommendation ITU-T X.682 (2020) | ISO/IEC 8824-3:2020, Information technology – Abstract

Syntax Notation One (ASN.1): Constraint specification.

– Recommendation ITU-T X.683 (2020) | ISO/IEC 8824-4:2020, Information technology – Abstract

Syntax Notation One (ASN.1): Parameterization of ASN.1 specifications.

– Recommendation ITU-T X.690 (2020) | ISO/IEC 8825-1:2020, Information technology – ASN.1

encoding rules: Specification of Basic Encoding Rules (BER), Canonical Encoding Rules (CER) and

Distinguished Encoding Rules (DER).

– Recommendation ITU-T X.691 (2020) | ISO/IEC 8825-2:2020, Information technology – ASN.1

encoding rules: Specification of Packed Encoding Rules (PER).
2.2 Additional references
– ECMA Standard ECMA-404 (2013) – The JSON Data Interchange Format.

– IETF RFC 2045 (1996), Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet

Message Bodies.

– ISO International Register of Coded Character Sets to be Used with Escape Sequences.

– ISO/IEC 10646:2003, Information technology – Universal Multiple-Octet Coded Character Set (UCS).

Rec. ITU-T X.697 (10/2017) 1
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ISO/IEC 8825-8:2018 (E)
3 Definitions

For the purposes of this Recommendation | International Standard, the following definitions apply:

3.1 Specification of Basic Notation

For the purposes of this Recommendation | International Standard, all the definitions in Rec. ITU-T X.680 |

ISO/IEC 8824-1 apply.
3.2 Information Object Specification

For the purposes of this Recommendation | International Standard, all the definitions in Rec. ITU-T X.681 |

ISO/IEC 8824-2 apply.
3.3 Constraint Specification

This Recommendation | International Standard makes use of the following terms defined in Rec. ITU-T X.682 |

ISO/IEC 8824-3:
a) component relation constraint;
b) table constraint.
3.4 Parameterization of ASN.1 Specification

This Recommendation | International Standard makes use of the following term defined in Rec. ITU-T X.683 |

ISO/IEC8824-4:
– variable constraint.
3.5 Basic Encoding Rules (BER)

This Recommendation | International Standard makes use of the following terms defined in Rec. ITU-T X.690 |

ISO/IEC 8825-1:
a) data value;
b) dynamic conformance;
c) encoding (of a data value);
d) receiver;
e) sender;
f) static conformance.
3.6 Packed Encoding Rules (PER)

This Recommendation | International Standard makes use of the following terms defined in Rec. ITU-T X.691 |

ISO/IEC 8825-2:
a) composite type;
b) composite value;
c) outermost type;
d) relay-safe encoding;
e) simple type;
f) textually dependent.
3.7 Additional definitions

3.7.1 abstract syntax value: A value of an abstract syntax (defined as a set of values of a single ASN.1 type)

which is to be encoded by JER or which is generated by JER decoding.

3.7.2 associated encoding instruction (for a type): A set of JER encoding instructions associated with a type.

3.7.3 effective value constraint (of an integer type): The smallest integer range that includes all the values of the

integer type that are permitted by the JER-visible constraints (see clause 7.2.7).

3.7.4 effective size constraint (of a bitstring type): The smallest integer range that includes the lengths of all the

values of the string type that are permitted by the JER-visible constraints (see clause 7.2.8).

2 Rec. ITU-T X.697 (10/2017)
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3.7.5 final encoding instructions (for a type): The set of JER encoding instructions associated with a type as a

result of the complete ASN.1 specification, and which are applied in producing encodings of that type.

3.7.6 inherited encoding instructions: A set of JER encoding instructions that are associated with the type

identified by a type reference.

3.7.7 JSON array: A series of JSON tokens that constitute an array structure as specified in ECMA 404, clause 7.

3.7.8 JSON member name string (of a component of a sequence, set, or choice type that is encoded as a JSON

object): The Unicode character string denoted by the name of the member of the JSON object identifying the

component in the JER encoding.

3.7.9 JSON number: A JSON token that is a number as specified in ECMA 404, clause 8.

3.7.10 JSON object: A series of JSON tokens that constitute an object structure as specified in ECMA 404, clause 6.

3.7.11 JSON string: A JSON token that is a string as specified in ECMA 404, clause 9.

NOTE – A JSON string is part of a JER encoding, it begins and ends with a quotation mark, may contain escapes, and is distinct

from the Unicode character string that it denotes.

3.7.12 JSON token: A Unicode character string that is one of the several kinds of tokens specified in ECMA 404,

clause 4.

3.7.13 JER encoding instruction: Notation used to change the JER encoding of a type.

3.7.14 JER-visible constraint: An instance of use of the ASN.1 constraint notation that affects the JER encoding of

a value.

3.7.15 octet: A group of eight consecutive bits, numbered from bit 8 (the most significant bit) to bit 1 (the least

significant bit).

3.7.16 prefixed encoding instruction: A JER encoding instruction that is assigned to a type using a type prefix.

NOTE – Prefixed encoding instructions can delete, replace, or add to the associated encoding instructions of a type.

3.7.17 targeted encoding instruction: A JER encoding instruction that is assigned to multiple types using a target

list in a JER encoding control section.

NOTE – Targeted encoding instructions can delete, replace, or add to the associated encoding instructions of multiple types.

4 Abbreviations

For the purposes of this Recommendation | International Standard, the following abbreviations apply:

ASN.1 Abstract Syntax Notation One
BER Basic Encoding Rules of ASN.1
JER JavaScript Object Notation Encoding Rules of ASN.1
PER Packed Encoding Rules of ASN.1
PDU Protocol Data Unit
5 Encodings specified by this Recommendation | International Standard

5.1 This Recommendation | International Standard specifies a set of encoding rules which can be used to encode

and decode the values of an abstract syntax defined as the values of a single (known) ASN.1 type. This clause describes

their applicability and properties.

5.2 JER encodings are always relay-safe provided the abstract values of the types EXTERNAL, EMBEDDED PDV,

and CHARACTER STRING are constrained to prevent the carriage of OSI presentation context identifiers.

5.3 If a type encoded
...