ISO/IEC 8825-1:2021(EN) Information technology — ASN.1 encoding rules — 

Part 1: Specification of Basic Encoding Rules (BER), Canonical Encoding Rules (CER) and Distinguished Encoding Rules (DER)
ISO/IEC 8825-1:2021 specifies a set of basic encoding rules that can 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, relative referred to as Abstract Syntax Notation One or ASN.1. These common encoding rules are also to be applied for decoding such transfer syntax in order to identify the data values being transferred. It also shares 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.
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