Illustrate maninthemiddle attack when Alice and Bob employ D

Illustrate man-in-the-middle attack when Alice and Bob employ Diffie-Hellman key exchange.

Solution

when Alice and Bob employ Diffie-Hellman key is in the man-in-the-middle attack of the exchange in a potentially fatal protocol attack on the Diffie-Hellman key exchange protocol becomes possible. The idea is based on forcing the parties to agree on a shared key that resides in a subgroup of the cyclic group Zq. If the order of the subgroup is small enough, an adversary can exhaustively search the subgroup, retrieve the secret key, and eavesdrop on the communication of Alice and Bob.The protocol depicted in is insecure against a man-in-the-middle attack. Suppose Alice and Bob wish to exchange keys, and Darth is the adversary. The attack proceeds as follows:

but instead Bob and Darth share secret key K1 and Alice and Darth share secret key K2. All future communication between Bob and Alice is compromised in the following is the Alice sends an encrypted message M: E (K2, M).

Darth sends Bob E (K1, M) or E (K1, M\'), where M\' is any message. In the first case, Darth simply wants to eavesdrop on the communication without altering it. In the second case, Darth wants to modify the message going to Bob.

The key exchange protocol is vulnerable to such an attack because it does not authenticate the participants. This vulnerability can be overcome with the use of digital signatures.