Editing ASN.1 (section)

{{merge from|X.690|discuss=Talk:ASN.1#Merge proposal|date=May 2025}}
{{Short description|Data interface description language}}
{{External links|date=July 2024}}
{{Infobox technology standard
| title             = ASN.1
| long_name         = Abstract Syntax Notation One  
| image             = 
| caption           = 
| status            = In force; supersedes X.208 and X.209 (1988)
| year_started      = 1984
| version           = (02/21)
| version_date      = February 2021
| preview           = 
| preview_date      = 
| organization      = [[ITU-T]]
| committee         = [[ITU-T Study Group 17|Study Group 17]]
| base_standards    = ASN.1
| related_standards = [[X.208]], [[X.209]], [[X.409]], [[X.509]], [[X.680]], [[X.681]], [[X.682]], [[X.683]]
| abbreviation      = 
| domain            = [[cryptography]], [[telecommunications]]
| license           = 
| website           = https://www.itu.int/rec/T-REC-X.680/
}}

'''Abstract Syntax Notation One''' ('''ASN.1''') is a standard [[interface description language]] (IDL) for defining [[data structures]] that can be [[serialization|serialized and deserialized]] in a cross-platform way. It is broadly used in [[telecommunications]] and [[computer networking]], and especially in [[cryptography]].<ref>{{Cite web|title=Introduction to ASN.1|url=https://www.itu.int:443/en/ITU-T/asn1/Pages/introduction.aspx|url-status=live|archive-url=https://web.archive.org/web/20210409122557/https://www.itu.int/en/ITU-T/asn1/Pages/introduction.aspx|archive-date=2021-04-09|access-date=2021-04-09|website=ITU|language=en-US}}</ref>

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, [[codec]]s, that decode or encode the data structures. Some ASN.1 compilers can produce code to encode or decode several encodings, e.g. packed, [[X.690#BER encoding|BER]] or [[XML]].

ASN.1 is a joint standard of the [[International Telecommunication Union Telecommunication Standardization Sector]] (ITU-T) in [[ITU-T Study Group 17]] and [[International Organization for Standardization]]/[[International Electrotechnical Commission]] (ISO/IEC), originally defined in 1984 as part of CCITT [[X.409]]:1984.<ref>{{Cite web|url=https://www.itu.int/ITU-T/recommendations/rec.aspx?rec=6947|title=ITU-T Recommendation database|website=ITU|access-date=2017-03-06}}</ref> In 1988, ASN.1 moved to its own standard, '''X.208''', due to wide applicability. The substantially revised 1995 version is covered by the '''X.680''' series.<ref>[https://www.itu.int/rec/T-REC-X.680-201508-I/en ITU-T X.680 - Specification of basic notation ]</ref> The latest revision of the X.680 series of recommendations is the 6.0 Edition, published in 2021.<ref>{{FOLDOC|ASN.1}}</ref>