I'm trying to implement the authentication system explains in this article Hmac User Authentication.
I don't understand the following part :
Server sends back: let MESSAGE = (USERNAME,REALM,SALT,SESSIONID,ENCRYPTED_SESSION_KEY) in auth:(MESSAGE,HMAC(SHA1,PASSHASH,MESSAGE)).
I don't know how to generate the SESSIONID and the ENCRYPTED_SESSION_KEY. And what is the "auth" ?