Every principal has an entry in the registry database that specifies a secret key. In the case of an interactive principal (that is, a user), the secret key is derived from the principal's password. Just as users need to keep their passwords secure by memorizing them (rather than writing them down, for example), a noninteractive principal also needs to be able to store and retrieve its secret key in a secure manner. The key management API provides simple key management functions for noninteractive principals.
While the key management routines themselves are relatively secure, it is up to the application to ensure the security of the file or other device used to store the key. By default, server principals that run on the same computer share a local key file; however, the key management API also allows principals to specify an alternative local file.
When users change their passwords, they are free to forget their old passwords. When a noninteractive principal changes its secret key, however, there may be clients with valid tickets to that principal that are encoded with the old key. To save clients the trouble of having to request new tickets to a noninteractive principal when the principal's key has changed, every key is flagged with a version number, and old key versions are retained until all tickets that could have been encoded with that key have expired.
Finally, if a noninteractive principal's key has been compromised, it may be invalidated (along with all the corresponding tickets held by any clients) by simply deleting it from the local key storage.
Note: The key management API is for use only by applications using the DCE shared-secret authentication protocol and the key-type DES.