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(Solved): Assume the cipher system is the permutation cipher on 4 letters. The following is the probability ...
Assume the cipher system is the permutation cipher on 4 letters. The following is the probability distribution of {A, B, C, D} in the message space. P[A] = 0.1, P[B] = 0.2, P[C] = 0.3, P[D] = 0.4 The following is the list of relative frequencies in the ciphertext. P[A] = 0.35, P[B] = 0.45, P[C] = 0.05, P[D] = 0.15 Find the key that minimizes the Euclidean distance between the probability distri- bution in the message space and that in the ciphertext, and write the key in the form of permutation matrix.
Expert Answer
Sol:- Substitution Ciphers Substitution ciphers replace units of plaintext with units of ciphertext. A simple example is the Caesar cipher, which specifies the substitution of each plaintext letter with the letter which is found some fixed number of