0

Below is an informal protocol narration of a simple authentication protocol. A sends to B a signed hash of message M, B's name and a nonce N. B knows that the message M is intended for him, that it originates from A and that it was sent as part of the same run.

A -> B: (M, A)
B -> A: N
A -> B: {| #(M,B,N) |}sA

But what will happen if we omit B's name?

A -> B: (M, A)
B -> A: N
A -> B: {| #(M,N) |}sA

I cannot think of a concrete scenario with a harmful attack. What attack could cause harm? A possible scenario is listed below:

A -> B: (M, A)
B -> A: N
A -> I: {| #(M,N) |}sA
I -> B: {| #(M,N) |}sA

There is no proof that the message was intended for B. So, intruder I can intercept the message signed by A and redirect it to B, authenticating I as A. But what is a harmful attack? For example in a bank-client interaction scenario?

Thank you.

1

There is no proof that the message was intended for B. So, intruder I can intercept the message signed by A and redirect it to B, authenticating I as A. But what is a harmful attack? For example in a bank-client interaction scenario?

If I understand you correctly, you've just described the first part of a Man In The Middle (MITM) attack.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.