IPSEC

Internet Key Exchange $($IKE$)$ Protocol Phase $1$ in Encryption mode looks like the diagram below:where $\}\_($K$1)$:$\}$ indicates public key encryption using Key $"$K$1"$ and E$($Msg$1,$ K$2)$ indicates symmetric key encryption of $"$Msg$1"$ sing key $"$K$2"$ and h$($Msg$2)$ indicates "hash" of $"$Msg$2".$Note that R$\_$A and R$\_$B are used interchangeably with R$\_($A$)$ and R$\_($B$)$ respectively in the multiple choices below.

Q: How is a shared secret established between Alice and Bob

It is established ahead of any message exchange

It is established by hashing $R_A$ and $R_B$

It is established by hashing IC and RC

It is established using Diffie Hellman method