Computer Science / / Cryptology Consider the following mutual authentication and

Question

Computer Science / / Cryptology

Consider the following mutual authentication and key establishment protocol, which uses a timestamp T and public key cryptography. For each of the following cases, explain whether or not the resulting protocol provides an effective means for secure mutual authentication and a secure session key K. Ignore replay attacks based solely on the clock skew. (a) Message 1: t[T, K]_Alice}Bob (b) Message 1: "Alice", {[T, K]^Alice}Bob (c) Message 1: "Alice", {[T, K]_Alice}Bob (d) Message 1: T, "Alice", {[T, K]_Alice}Bob (e) Message 1: "Alice", {[T, K]_Alice}Bob and let K = h(T)

Explanation / Answer

Part a is secure .it provides effective mean for secure mutual authentication and secure session key. It having Timestamp and session key K encrypted with Alice private key and encrypted with Bob public key .

b) message 1 is secured because the complete message is encrypted with Bob public key.

c) message 1 is not secured because content of message is changed by any interceptor .

d) message 1 is not secured because intruder gives new timestamp to message and also change the content of message.

e) this message is secure because session key is calculated on the basis of function on timestamp values. This function is known mutually so nobody knows session key.

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