To understand how DES credentials are created and how they work, you need to distinguish between the credential itself and the information that is used to create and verify it.
Credential information: The data that is used to generate a DES credential and by the server to verify that credential.
DES credential: The bundle of numbers that is sent by the principal to the server to authenticate the principal. A principal's credential is generated and verified each time the principal makes an NIS+ request. See DES Credential in NIS+ for a detailed description of the DES credential.