BER and DER of ASN.1

BER: basic encoding rules
DER: distinguished  encoding rules
ASN: abstract syntax notation

DER is a subset of BER, and BER is a subset of ASN.1

DER encoding for each ASN.1 value is unique
BER encoding for an ASN.1 value may be multiple.



[ref]
http://www.rsa.com/products/bsafe/documentation/certj212html/certj/dev_guide/group__CERTJ__STDS__ENCODING.html