Consider the following protocol a Explain the protocol b Can

Consider the following protocol:

a. Explain the protocol.

b. Can you think of a possible attack on this protocol? Explain how it can be done.

c. Mention a possible technique to get around the attack – not a detailed mechanism, just the basics of the idea.

A KDC: ID De N KDC A: E(Ka, [Ks]IIIDBIIN E(Kb, [Ks A B E(Ko, [Ks DA]) B A: E(Ks, N2)A. B: E(Ks, f(N2)) DA]))

Solution

Answer:

a) In this protocol , A requests a session key which it can use between A and B for the KDC as : A ---> KDC : IDa || IDB || N 1.

b) Yes this protocol is vulnerable to attacks . Like if an intruder somehow get an old key K, he/she can replay the message to B by pretending to be sender A.

c) As this is the vulnerability of this protocol , we can attach Timestamps with the message being sent over the channel which can encounter the attack.