Suppose that someone suggests the following way to confirm that the two of you a

Question

Suppose that someone suggests the following way to confirm that the two of you are both in possession of the same secret key. You create a random bit string the length of the key, XOR it with the key, and send the result over the channel. Your partner XORs the incoming block with the key (which should be the same as your key) and sends it back. You check and if what you receive is your original random string, you have verified that your partner has the same secret key, yet neither of you has ever transmitted the key. Is there a flaw in this scheme?

*Please dont only give me the answer but also explain WHY, maybe use "//" or "*" Important homework assignment

Explanation / Answer

Yes, an attacker can listen the communication and find the key in following way,- Let A and B are the partners, and K is the key of size N. 1> A generates random string R 2> Calculates S : = K XOR R 3> send S to B 4> B calculates S1:= S XOR K 5> sends S1 to A 6> A validates whether R is equal to S1 or not? So an attacker listening the conversation will have both S and S1. So, he will compute the key as follows, K:= S1 XOR S

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