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A lot of modern cryptography is based on some mathematical assumptions and aims to achieve what is called Computational Security. That means that the adversary (Eve) could get some information about the plaintext with a negligible probability and the adversary is modeled as someone with bounded computational power, storage and bounded time. So all the ...


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Well, as it says in your link the problem is authentication. So somehow Alice and Bob must set up an authenticated channel. One way of implementing such a channel is by Alice and Bob holding each others public verification key for a signature scheme. A CA would probably not hold a secret key for Alice and Bob. However, using a CA to get an authentic copy ...


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Firstly, PKI makes use of a private key and a public key. The private key is known only to the user, while the public key is communicated securely via the use of certificates. To provide authentication and non-repudiation, users may sign a message with their private keys and obtain a digital signature. Any other users can verify that the signed signature is ...


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Guess the catch in the video is in how the participants exchange details 'publicly'. If the Man-In-The-Middle can intercept and manipulate what is being 'publicly' shared, then the attempt to eavesdrop would still be successful.


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The question Alex linked in comments explains why authentication works to prevent a man-in-the-middle attack on Diffie–Hellman. So, whenever you can do the key exchange in an authenticated channel, you can be sure there is no MitM attack. (Assuming DH problem remains unbroken, of course.) Now, your questions: Is one solution for both Alice and Bob ...


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The problem about Man-in-the-Middle attack on Diffie-Hellman is that both sides are not confident about other side's public key (g^a and g^b). If they were sure that they have correct public key of their's friend Man-in-the-Middle attack wouldn't be possible, because MITM attack is based on the forgery of public keys by adversary! If for instance Bob and ...


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DrLecter is right. It all boils down to making sure to use the right public key. In fact this is the same for any public key cryptosystem be it RSA elGamal or ECC variants thereof. A MAC or whatever other construction local to your system won't do the job. The MAC e.g. can only make sure the last "editor" of the message knew the symmetric key the message ...


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No, because Bob cannot know for sure who send the public key in the first place. So impersonation may still be an issue, even if man-in-the-middle attacks are not possible. If the communication is over a channel that can only be eavesdropped by Eve (i.e. Even cannot send anything to Bob within Bob knowing it is not from Alice), then this is secure. But ...


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…what if I only verify the signature of one end? Bob would not be able to know if he is looking at a signature by Eve, or if it’s a valid signature coming from Alice. In case if Eve is messing with the exchange, Eve would be able to inject her own (as it is handled non-authenticated) and Eve would be able to verify that it’s Bob on the other end (which ...



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