I'm studying a one-pass key establishment protocol. Let be A client and B the Server.
A sends to B:
t is a timestamp requested for freshness,
k is the ephemeral key that will be used for the communication.
My question is, what is b? I think an Identifier of the Server, but what is the utility?
I attach the image of the page of the book on which I'm studying. Maybe the problem is that My English is not well, so I don't understand fully the text.
The book states: "and a target identifier to prevent undetectable message replay back on A immediately."
Can you explain this sentence?