where NA and NB are nonces, and #$($NA$,$ NB$)$ is a symmetric key based on the hash

of NA and NB$,$ and pk$($A$)$ is the public key of A$.$ Is it possible for the attacker to

learn M without knowing the private key of A$?$ If so$,$ give an attack in Alice$-$Bob

Notation. If not, explain why.