Computer Security lecture 3

Computer security- authentication protocols

Reference: Modelling and analysis of security protocols by Peter Ryan and co

3 types of authentication

Aliveness

Mutual communication

Message agreement

This is a set up- can see bob and alice communicate through server

So, what is the live aliveness?

Simply requires that only that an agent is detected to be alive and running in some protocol session

Mutual is same but goes through server first

Entity authentication- 2 agents agree on top of mutual communication that some communicated data

Message origin

Authentication directionality

One way- only 1 agent authenticates the other

2 way- authenticate each other

So can see A is telling it is A and sending data with k straight to be

B sends that back with the key to server

As well as the data given by A

Nonce of A is being sent from A encrypted with public key of B
B then sends this back but with nonce of b, signed with public key of A
A then sends Nonce of B back to B
this shows they are communicating with each other

2 way- easier to understand