Homework #1
                              (CS685-02, Sp'02)
                              (Due date: 3/21/02)

Encryption/ General Security
        1)Using the secret key, public key methods which you learnt, design
        a protocol (Sequence of messages exchanged between two entities) which
        can provide
 
        a)Privacy
        b)Authentication
        c)Message Integrity
        d)Non- repudiation
                Explain each step of your protocol and also explain how these
steps
        provide the above-mentioned characteristics. State explicitly all the
        assumption made, if any.
 
        2)List and Explain the attacks on authentication protocols
                a)Is your protocol immune to these attacks? Explain.
                b)Modify your protocol to make it immune to "Man in the Middle
                attack" and "Replay attack".