ISO/IEC 8825-1:2021 PDF

Information technology — ASN.1 encoding rules — Part 1: Specification of Basic Encoding Rules (BER), Canonical Encoding Rules (CER) and Distinguished Encoding Rules (DER)

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Title (English):

ISO/IEC 8825-1:2021

Information technology — ASN.1 encoding rules — Part 1: Specification of Basic Encoding Rules (BER), Canonical Encoding Rules (CER) and Distinguished Encoding Rules (DER)

Document status:: Active
Format:: Electronic (PDF)
Number of pages:: 28
Publication date:: June 30, 2021
Edition:: ISO/IEC IS 8825 edition 6 version 1
ICS:: 35.100.60

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Description (English):

This document specifies a set of basic encoding rules that may be used to derive the specification of a transfer syntax for values of types defined using the notation specified 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, and Rec. ITU-T X.683 | ISO/IEC 8824-4, collectively referred to as Abstract Syntax Notation One or ASN.1. These basic encoding rules are also to be applied for decoding such a transfer syntax in order to identify the data values being transferred. It also specifies a set of canonical and distinguished encoding rules that restrict the encoding of values to just one of the alternatives provided by the basic encoding rules.

Technical details

Technical committee: ISO/IEC JTC 1/SC 6 - Telecommunications and information exchange between systems
SKU: ISO/IEC 8825-1:2021

Abstract

Overview

ISO/IEC 8825-1:2021 specifies encoding rules for Abstract Syntax Notation One (ASN.1). It defines the Basic Encoding Rules (BER) used to produce a transfer syntax for ASN.1 types and the two restricted variants - Canonical Encoding Rules (CER) and Distinguished Encoding Rules (DER) - that remove sender choices to produce a unique representation. The standard is aligned with ITU‑T X.690 (02/2021) and is the authoritative reference for encoding/decoding ASN.1 defined data values.

Key Topics

Scope & conformance: Rules for encoding and decoding values of ASN.1 types defined in ISO/IEC 8824‑1..4 (ITU‑T X.680–X.683).
Structure of an encoding: Identifier octets, length octets, contents octets and end‑of‑contents markers.
Primitive and constructed types: Encoding rules for boolean, integer, real, bit string, octet string, null, sequence, set, choice, object identifier and character string types.
BER vs CER vs DER:
- BER: Flexible; offers multiple valid encodings for the same value.
- CER/DER: Restrict BER alternatives to enforce a single canonical encoding. CER is optimized for streaming/large values; DER is optimized for compactness and rapid parsing of small values.
Restrictions and examples: Specific constraints on boolean, real, string, time types and set/sequence ordering; annexes provide encoding examples and real number illustrations.
Identification & registration: Annex summarizing object identifier assignments and encoding rule identification.

Applications

ISO/IEC 8825-1:2021 is essential for systems that need standardized binary representation of structured data:

Security & certificates: Interoperable encoding of cryptographic objects and certificates.
Network protocols & telecommunications: Encoding of protocol PDUs and management data.
Messaging & data interchange: S/MIME, LDAP, and other standards that rely on ASN.1 transfer syntaxes.
Implementers and tool vendors: Developers of ASN.1 compilers, parsers, libraries, protocol stacks, and conformance test suites.

Who should use it:

Protocol designers specifying transfer syntaxes
Software engineers implementing ASN.1 encoders/decoders
Security engineers ensuring canonical encodings for digital signatures
Standards authors and test labs validating interoperability

Related Standards

ISO/IEC 8824‑1..4 (ITU‑T X.680–X.683) - ASN.1 notation and type definitions
ITU‑T X.690 - Equivalent text for BER/CER/DER in the ITU series

ISO/IEC 8825-1:2021 is the definitive resource for anyone who must encode, decode or validate ASN.1 data reliably across systems.

Related standards

Mentioned in the description and other ISO standards

Abstract

Overview

Key Topics

Scope & conformance: Rules for encoding and decoding values of ASN.1 types defined in ISO/IEC 8824‑1..4 (ITU‑T X.680–X.683).
Structure of an encoding: Identifier octets, length octets, contents octets and end‑of‑contents markers.
Primitive and constructed types: Encoding rules for boolean, integer, real, bit string, octet string, null, sequence, set, choice, object identifier and character string types.
BER vs CER vs DER:
- BER: Flexible; offers multiple valid encodings for the same value.
- CER/DER: Restrict BER alternatives to enforce a single canonical encoding. CER is optimized for streaming/large values; DER is optimized for compactness and rapid parsing of small values.
Restrictions and examples: Specific constraints on boolean, real, string, time types and set/sequence ordering; annexes provide encoding examples and real number illustrations.
Identification & registration: Annex summarizing object identifier assignments and encoding rule identification.

Applications

ISO/IEC 8825-1:2021 is essential for systems that need standardized binary representation of structured data:

Security & certificates: Interoperable encoding of cryptographic objects and certificates.
Network protocols & telecommunications: Encoding of protocol PDUs and management data.
Messaging & data interchange: S/MIME, LDAP, and other standards that rely on ASN.1 transfer syntaxes.
Implementers and tool vendors: Developers of ASN.1 compilers, parsers, libraries, protocol stacks, and conformance test suites.

Who should use it:

Protocol designers specifying transfer syntaxes
Software engineers implementing ASN.1 encoders/decoders
Security engineers ensuring canonical encodings for digital signatures
Standards authors and test labs validating interoperability

Related Standards

ISO/IEC 8824‑1..4 (ITU‑T X.680–X.683) - ASN.1 notation and type definitions
ITU‑T X.690 - Equivalent text for BER/CER/DER in the ITU series

ISO/IEC 8825-1:2021 is the definitive resource for anyone who must encode, decode or validate ASN.1 data reliably across systems.

ISO/IEC 8825-1:2021 PDF

Technical details

Abstract

Overview

Key Topics

Applications

Related Standards

Related standards

Abstract

Overview

Key Topics

Applications

Related Standards

Related standards

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