Consider the following protocol that involves both public$-$key operations and symmetric$-$key operations. Suppose that A has a private key prv$($A$)$ and a public key pub$($A$).$ Suppose that B has a private key prv$($B$)$ and a public key pub$($B$).$ Assume both A and B know each other$$s public key. A wants to send B some message M$.$ A selects a random symmetric key K and sends B the following two messages:

$--$ Epub$($B$)($K$)|$Sigprv$($A$)($Epub$($B$)($K$))$

$--$ EK$($M$)$

where EX$($Y$)$ denotes encryption of message Y using key X$,$ SigX$($Y$)$ denotes signature on message Y using key X$,$ and $|$ denotes concatenation.

Which of the following statements are true and which are false? Answer the following questions from $1-3.$

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$1.$ Only A and B can decipher to obtain the message M$.$