Ans Doc381


Secure Data Exchange
SupposeAlice and Bob want to exchange data securely. They want confidentiality (encryption), integrity and authentication (MAC), and non-repudiation (Digital Signatures).
They want the bulk encryption to be done using symmetric cipher “X”, with MAC function “H”.
Both have signed and certified RSA keys. You may assume both parties have already exchanged and verified the validity of the public RSA keys of the other party.
1. Detail the series of steps involved in the initial key exchange, and the steps involved in sending a message M from Alice to Bob, both at Alice’s and at Bob’s end.
Your answer should be in the format of messages sent between Alice and Bob,
e.g.: Alice: Ek(M) -> Bob
“Alice encrypts message M using symmetric key K and cipher X, and sends the result to Bob”
With descriptive text to make sure all the steps taken are clear.
All parts are not to be solved programmatically, but instead by hand following the processes shown during lectures. The level of detail required to be shown in the workings is the same as in the lecture examples.