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ASN.1
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<p>Abstract Syntax Notation One (ASN.1) is a standard <a href="/facts/Interface_description_language/FpByLf4X">interface description language</a> (IDL) for defining <a href="/facts/Data_structures/yNsNvL1I">data structures</a> that can be <a href="/facts/Serialization/T00auFvv">serialized and deserialized</a> in a cross-platform way. It is broadly used in <a href="/facts/Telecommunications/vxoj1cxR">telecommunications</a> and <a href="/facts/Computer_networking/3w5RM99p">computer networking</a>, and especially in <a href="/facts/Cryptography/e94PEVau">cryptography</a>. </p><p>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 <a href="/facts/Human-readable/GDE1fpHT">human-readable</a> and <a href="/facts/Machine-readable/YA2qAshK">machine-readable</a>, an ASN.1 compiler can compile modules into libraries of code, <a href="/facts/Codec/C7b7Am8t">codecs</a>, that decode or encode the data structures. Some ASN.1 compilers can produce code to encode or decode several encodings, e.g. packed, <a href="/facts/X.690/sNL76pTs">BER</a> or <a href="/facts/XML/clNgUfWk">XML</a>. </p><p>ASN.1 is a joint standard of the <a href="/facts/International_Telecommunication_Union_Telecommunication_Standardization_Sector/9nJwkPYx">International Telecommunication Union Telecommunication Standardization Sector</a> (ITU-T) in <a href="/facts/ITU-T_Study_Group_17/I8DNd2B2">ITU-T Study Group 17</a> and <a href="/facts/International_Organization_for_Standardization/IacYR7Yg">International Organization for Standardization</a>/<a href="/facts/International_Electrotechnical_Commission/hSK0kjwI">International Electrotechnical Commission</a> (ISO/IEC), originally defined in 1984 as part of CCITT X.409:1984. 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–X.683 series. The latest revision of the X.680 series of recommendations is the 6.0 Edition, published in 2021. </p>