When used to create DES credential information, nisaddcred goes through a two-part process:
Forming the principal's Secure RPC netname. A Secure RPC netname is formed by taking the principal's user ID number from the password record and combining it with the domain name (firstname.lastname@example.org, for example).
Generating the principal's private and public keys.
To encrypt the private key, nisaddcred needs the principal's Secure RPC password. When the nisaddcred command is invoked with the -des argument, it prompts the principal for a Secure RPC password. Normally, this password is the same as the principal's login password. (If it is different, the user will have to perform additional steps when logging in, as described in Secure RPC Passwords and the Login Password Problem in NIS+.)
The nisaddcred command generates a pair of random, but mathematically related 192-bit authentication keys using the Diffie-Hellman cryptography scheme. These keys are called the Diffie-Hellman key-pair, or simply key-pair for short.
One of these is the private key, and the other is the public key. The public key is placed in the public data field of the cred table. The private key is placed in the private data field, but only after being encrypted with the principal's Secure RPC password.
The principal's private key is encrypted as a security precaution because the cred table, by default, is readable by all NIS+ principals, even unauthenticated ones.