I'm having trouble with the following question:
- $X(A) \rightarrow B:(A,N_X)$
- $B \rightarrow X(S):(B,((A,N_X,T_B),K_{BS}),N_B)$
- $X(A) \rightarrow B:(((A,N_X,T_B),K_{BS}),(N_B,N_X))$
Give two very good reasons why this attack works, in terms of the properties of the messages being exchanged and their content.
$X$ is the attacker in this case.
$A$ and $B$ are the names of two agents, $S$ is the name of a trusted server, $N_X$ denotes a nonce created by entity $X$, $T_X$ denotes a timestamp created by entity $X$, $K_{XY}$ denotes a key shared between entities $X$ and $Y$
If anyone can help at all, I would greatly appreciate someone going through this question with me step by step.
From this I have understood that $B$ relays the encrypted message back and thinks everything is okay. The attacker doesn’t care about verifying the message. It gets the key and communicates with $B$ where $B$ thinks it is $A$ who has got the key through the server.
I just want to make sure that i have understood it correctly.