Can you please explain me what is the reason of using nonces in the Needham-Schroeder and in the Kerberos protocols for Key Transport.
In particular :
- Can you explain me the use of $N_A$?
And also, I suppose $N_B$ is used for the scope of letting $B$ know that $A$ shares the same key $K_{AB}$ and was able to decipher the value of $N_B$, alter it and encrypt it back by using $K_{AB}$.
- Is this assumption correct?
And finally:
- How does the use of the nonces provide more security to the protocol?
Here you can find more details about the two protocols.