. The following is a key exchange protocol used by two clients,A and B, to obtain a symmetric key???, using a trusted server, S.Assume that A and B had previously obtained the symmetric keys ???and ??? securely with the server. Also assume that anyone cansecurely obtain a secret symmetric key with the server. I. A → S :A, B II. S → A : (???) ??? ,( ???) ??? III. A → B : (???) ??? , A •Identify the attack that can be executed against this protocol,assuming that an attacker C can eavesdrop, block, or modify allmessages. The attacker also has access to old (expired) keys.
Note: Show me the answer with mathematical way andexplanation
