Authentication protocols assume the availability of a data encryption mechanism, parameterized by a so-called crypto-variable or key. In fact, it is the knowledge of such a key that is the concrete manifestation of the abstract notion of authentication. One mechanism that is frequently used is the Data Encryption Standard (DES), though the DCE security architecture supports other cryptographic algorithms. Your version of DCE security may use DES for data privacy or for principal authentication and data-integrity checking; or it may use another encryption mechanism, or no encryption at all. Consult the documentation supplied by your DCE vendor for specific information.