You have the message sequence below.

Msg1. AS :{A, N1, Message1, h(A, N1, Message1)}{PKS}

Msg2. SB :{A, N1,Ks, Message1, h(A, N1, Message1)}{PKB}

Msg3. BA : B, N1, Ks, Message2, h(B, N1, Message2)

Msg4: AB : {Data}{Ks}

Whereas:

h(m) represents the digest of the message (m).

{m}{K} represents the encryption of message (m) using the key (K)

PK is public key

N1 is a random number.

Based on your understanding of the protocol above; explain the followings:

1. What are the main problems in Msg3?
2. The reason why N1 is included in Msg3.
3. The reason why "A" is included in the digest calculation in messages 1 and 2.