Question :
Suppose alice, bob and carol want to use secret key technology to authenticate each other.
If they all use the same key, K, then bob would impersonate carol to alice. suppose instead that each had their own secret key to that alice uses KA, bob uses BA and carol uses KC.
This means that each one to prove their identity, responds to a challenge with a function of his or her secret key. is this more secure than having them all use the same secret key?