(Solution Download) a) Given are two protocols in which the sender?s party performs the following operation: Protocol A:


a) Given are two protocols in which the sender?s party performs the following operation: Protocol A: y = ek1 (x||H(k2||x)), where x is the message, H is a hash function such as SHA-1, e is a symmetric-key encryption algorithm, ?||? denotes simple concatenation, and k1, k2 are secret keys which are only known to the sender and the receiver. Protocol B: y = ek(x||sigkpr (H(x))), where k is a shared secret key, and kpr is a private key of the sender (not shared with the receiver). Provide a step-by-step description (e.g., with an itemized list) of what the receiver does upon reception of y. b) State whether the following security services: ? confidentiality ? integrity 8 ? non-repudiation (preventing an entity from denying previous commitments or actions) is given for each of the two protocols given in the previous problem.

 







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