(1) A -> S : A, B

(2.1) S -> A : {Ts, Kab, B}Kas

(2.2) S -> A : {Ts, Kab, A}Kbs

(3.1) A -> B : {Ts, Kab, A}Kbs

(3.2) A -> B : {A, Ta} Kab

(4) B -> A : {Ta}Kab

The model of the above protocol could be composed of several variables and processes (or agents). The protocol shall ensure authentication and secrecy. Such properties shall be verified against an intruder J with the following capabilities: J is a known agent, it can act either as initiator or as responder of a protocol session; J can eavesdrop and store any message sent by any agent; J can exploit its knowledge to generate new messages or use previously stored messages as they are.

Task 2.1: (25%) Model the security protocols authentication and secrecy in Casper. You should produce a Casper file (*.spl), convert it into a FDR script in Casper and finally model check the two properties in FDR.

Task 2.2: (5%) Produce a mini report to analyse the result from FDR. For example, if FDR can find an attack, you should simply talk about how the attack can be implemented. If no attack is found, you should conclude that the protocol holds the properties. The report should be 500 words maximum