We were given this exercise, which asks us to identify the types of keys used on this diagram:
The solution was
Kxa -> A's private key
Kya -> A's public key
KxB -> B's private key
My question is, how is it possible that B knows the contents the first message coming from A since it was encrypted with A's private key ? Also, B replies back to A encrypting the message with A's public key which is encrypting a message using B's private key.. I thought private keys were meant to be used to decrypt messages ecrypted by public keys.
I dont understand how come they know each other's private keys.