CER

Canonical Encoding Rules

CER (Canonical Encoding Rules) is 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 (together with DER) selects just one encoding from those allowed by the basic encoding rules, eliminating rest of the options. CER is useful when the encodings must be preserved; e.g., in security exchanges.