# Tag Info

3

I'm answering this based on the TLS v1.2 certificate based client authentication feature. Other protocols may vary in the details. Can anybody tell me what is being sent from the user's side for getting authentication from the server? The overhead to a normal handshake consists only of the user's certificate (+ intermediate certificates eventually, ...

3

That doesn't hide Bob's identity from eavesdroppers. (The OP mentioned in chat that the OP isn't trying to do that.) I can no longer spot any other problems with the key exchange part. The encryption/decryption of application level data is vulnerable to arbitrary replays and reflection and dropping. ​ The public MAC input should indicate direction and ...

1

Can anyone suggest an example of an application where we need to know who sent the data but it doesn't really matter if they later deny that they sent it? I would argue that most situations where you need authentication are like this. You very rarely need to be able to prove anything to third parties. For example, if you have a TLS connection to a ...

0

When you are talking to yourself. In some applications, two processes running as the same user communicate via TCP sockets on localhost. It is important to verify the identity of one's peer here to avoid local exploits, but non-repudiation is irrelevant.

3

To answer your first question, the incrementation is required in order to prevent spoofing of that message. An attacker could send back the same encrypted nonce claiming to be Bob. However, if Bob incriments the nonce and sends it back encrypted, Alice would know for sure that Bob has received the nonce and has incremented it. Now, Alice encrypting the ...

6

My only idea is that B authenticates himself to A, because if A later decrypts it, A will see whether B was able to decrypt it. But why would you need to increment the nonce? Correct, that's the idea. If B didn't need to increment the nonce and just encrypted the same value, the message sent back would be the same that A sent, so an attacker would be ...

3

I'll give you a hint, and you can work out the details yourself. Take any $m_1,m_2,m_3$ of length $n$ (where $n$ is the block length), with $m_1\neq m_2$. Query the oracle with $m_1$, then query the oracle with $m_2$, and finally query the oracle with $m_1\|n\|m_3$. Work through this, and you can find a message and its forgery.

1

Simply put, there are two key-pairs for DHE_RSA instead one key-pair of RSA_RSA. For example, for AES128_CBC_SHA(long name is RSA_RSA_AES128_CBC_SHA), you have one key-pair for both key-exchange and authentication. for ECDHE_RSA_AES_CBC_SHA, you have two key-pairs. The ECC key-pair is temporary for key-exchange. The RSA key-pair from cert is used for ...

Top 50 recent answers are included