ASN.1/DER processing

SET messages are described using ASN.1 and encoded using DER. ASN.1, which stands for Abstract Syntax Notation One, is a syntax for describing datatypes. DER, which stands for Distinguished Encoding Rules, is a set of rules describing an external data format for canonically representing ASN.1 datatypes as byte streams.

SETREF provides an ASN.1/DER processing runtime (a2c) which is used by most of SETREF. This runtime may also be used by the application programmer, for instance for decoding X.509 Distinguished Names.

The data structures used by a2c will become familiar to the application programmer because they are used throughout SETREF. The section on SETREF Datatypes provides an example of the mapping between the ASN.1 types defined in the SET specification and the data structures used by a2c.

There are important reasons for using the native types of the ASN.1/DER processing runtime. First, most datatypes used by SETREF are defined in the SET specification using ASN.1. Second, since nearly all data processed by SETREF is at one time or another DER encoded using the ASN.1/DER runtime, it is most convenient to use a2c's native data structures.