Choose the correct answer. One of the ways to compromise Lamport's one time authentication
scheme is as follows.
(a) Capture an authentication message for one round; do not allow this message to proceed to the
verifier. Use this message for authentication before the cot user has another opportunity for
authenticating.
(b) Launch a denial-of-service attack against the authentication server.
(c) Make sure that system clocks at the claimant and the verifier are never synchronized.
(d) Simply copy an authentication message in one round and replay it in the next round.
(e) All of the above
(f) None of (a), (b) or (c)



Answer :

The correct answer to the question regarding compromising Lamport's one-time authentication scheme is option (d) Simply copy an authentication message in one round and replay it in the next round. Here's a step-by-step explanation of why this is the correct choice: 1. Lamport's one-time authentication scheme relies on using unique, one-time authentication messages for each round of authentication. 2. If an attacker copies an authentication message in one round and replays it in the next round, it compromises the uniqueness of the authentication message. 3. By replaying the same authentication message, the attacker can impersonate the legitimate user and gain unauthorized access, as the verifier will mistakenly accept the repeated message as a valid authentication. 4. This type of attack violates the fundamental principle of using one-time authentication messages to ensure security in Lamport's scheme. Therefore, choosing option (d) as the correct answer highlights a significant vulnerability in Lamport's one-time authentication scheme, demonstrating how an attacker can compromise the system by replaying copied authentication messages.