Cryptographic Protocols & Key Management

Question 1

what is a cryptographic protocol?

Answer 1

a specification of how to apply cryptographic primitives and in what precise sequence of message-passing and actions between entities so that a specific set of security goals are met

Question 2

what does a cryptographic protocol need to specify? (4)

Answer 2

1. protocol assumptions - what needs to have happened before the protocol is run?
2. protocol flow - who sends a message to whom and in what order?
3. protocol messages - what information is exchanged at each step?
4. protocol actions - what needs to be done between steps?

Question 3

what is freshness of reply?

Answer 3

the timeliness or currentness of a response

Question 4

what can be used to ensure freshness of reply? (2)

Answer 4

Nonce (number only used once) & timestamps

Question 5

what are the objectives of authentication and key establishment protocols? (2)

Answer 5

1. Mutual entity authentication
2. Establishment of common symmetric key

Question 6

what is the Diffe-Hellman key aggrement protocol?

Answer 6

a method used to establish a shared secret key between two parties over an insecure communication channel