In §21.4.5 DASS Delegation we describe how Alice manages to simultaneously establish a session key with Bob, pass along her login private key to Bob, and authenticate to Bob. Analyze the protocol as described. Why can’t an eavesdropper discover Alice’s login private key? Why can Bob discover Alice’s login private key? How can Bob be sure that the authenticator came from Alice? In the non-delegation case, he knows that only Alice knows the session key (that encrypted the authenticator) because the session key, when passed to Bob, was signed with Alice’s private key. But the signing step is omitted in the delegation case.
