Question

The conditions for perfect secrecy are

(a) Only one key transforming message should exist

(b) All keys should be equally likely

(c) One key transforming message to each cipher text & all keys should be equally likely

(d) None of the mentioned

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I'm obligated to ask this question of Cipher Systems and Secrecy of Cipher Systems in portion Spread Spectrum Techniques of Digital Communications

Answer 1

Correct answer is (c) One key transforming message to each cipher text & all keys should be equally likely

Easy explanation: The conditions for perfect secrecy are, there is only one key transforming message to each cipher text and all keys should be equally likely.