Canonical Encoding Rules

protocol, standard (CER) A restricted variant of BER for

producing unequivocal transfer syntax for data structures

described by ASN.1.

Whereas BER gives choices as to how data values may be

encoded, CER and DER select just one encoding from those

allowed by the basic encoding rules, eliminating all of the

options. They are useful when the encodings must be

preserved, e.g. in security exchanges.

CER and DER differ in the set of restrictions that they

place on the encoder. The basic difference between CER and

DER is that DER uses definitive length form and CER uses

indefinite length form.

Documents: ITU-T X.690, ISO 8825-1.

See also PER.

(1998-05-19)