Problem based on a pub$/$priv key based authentication set$-$up in SSH$.$ A passphrase was set during the set$-$up$.$ Now conduct a cryptoanalysis for this authentication process. After the authentication set$-$up completed, a user starts to log into a remote server by SSH$.$ If there is a Man$-$in$-$the$-$middle, what can he hear during this remote log$-$in authentication process?

A plain random number

An encrypted msg by the client's public key

A password

An encrypted msg by the client's private key

An encrypted public key

A passphrase