Abstract Syntax Notation One

Also known as ASN.1

Abstract Syntax Notation One (ASN.1) is a standard interface description language (IDL) for defining data structures that can be serialized and deserialized in a cross-platform way. It is broadly used in telecommunications and computer networking, and especially in cryptography.

Key facts

Technology standard.title: ASN.1
Technology standard.long_name: Abstract Syntax Notation One
Technology standard.status: In force; supersedes X.208 and X.209 (1988)
Technology standard.year_started: 1984
Technology standard.version: (02/21)
Technology standard.version_date: February 2021
Technology standard.organization: ITU-T
Technology standard.committee: Study Group 17
Technology standard.base_standards: ASN.1
Technology standard.related_standards: X.208, X.209, X.409, X.509, X.680, X.681, X.682, X.683
Technology standard.domain: cryptography, telecommunications
Technology standard.website

~29 min read

Article

22 sections

Contents

Structure
Language support
Applications
Encodings
Encoding Control Notation
Relation to Privacy-Enhanced Mail (PEM) Encoding
As computer files
Example
Module and constraint
Example PDU
Example encoded in DER
Example encoded in XER
Example encoded in PER, either aligned or unaligned
Tools
Online tools
Comparison to similar schemes
Schema translation
Schema-optional formats
Protocol definitions on different levels
See also
References
External links

Protocol developers define data structures in ASN.1 modules, which are generally a section of a broader standards document written in the ASN.1 language. The advantage is that the ASN.1 description of the data encoding is independent of a particular computer or programming language. Because ASN.1 is both human-readable and machine-readable, an ASN.1 compiler can compile modules into libraries of code, codecs, that decode or encode the data structures. Some ASN.1 compilers can produce code to encode or decode several encodings, e.g. packed, BER or XML.