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How many combinations of keys can be constructed from a 72 ciphertext stream cipher?(a) 4271(b) 7345(c) 3291(d) 2556The question was asked at a job interview.Asked question is from Cryptography in chapter Number Theory and Cryptography of Discrete Mathematics |
Answer» CORRECT answer is (d) 2556 For EXPLANATION: For stream cipher, if there are N ciphertexts then there are n*(n−1)/2 combination of KEYS to be made. = \(72*\frac{72-1}{2}\) = 72*35.5 = 2556. |
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