Consider the following encryption scheme to provide confidentiality. A wants to

Question

Consider the following encryption scheme to provide confidentiality. A wants to send a message M, a 64-bit message, to B, and wants to make sure BG can't read M. B generates a random 64-bit number R and the step (1) communication from B to A is R. AXORs M with R to get the ciphertext C and the step (2) communication from A to B is C. When B receives C, he XORs C with R to get M. Is this a good scheme? Give a YES/NO answer. If you said NO, explain your answer i.e. explain what you think is the single biggest weakness of the scheme

Explanation / Answer

Ans - According to me in this scheme there is a big mistake of man in middle attack .

In this b generates a random number R and sends it to A . Suppose a person sitting between a and b can read all the conversations between A and B . so he will get the random number R and when A xor the message M with R and sends it to B B decodes it by using the Random number R by xoring it. The man in middle can also capture the cipher text and easily decode this message as he also has the same random number that B sent to A so in this technique there is no garuantee of sending the message confidentially .

so according to me it is not a good scheme .

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