JASN is a runtime library of Java Classes used to encode and decode ASN.1 values according to different encoding rules.

ASN.1 is a specification language used by many protocols to define a variety of data types, from simple types to structured types. Some Encoding Rules are defined to transform the ASN.1 values to an octet string.

A very good introduction on ASN.1 and its encoding rules may be found in A Layman's Guide to a Subset of ASN.1.

JASN currently supports the following encoding rules:

• BER: Basic Encoding Rules
that give one or more ways to represent any ASN.1 value as an octet string.
• DER: Distinguished Encoding Rules
that give exactly one way to represent any ASN.1 value as an octet string.