(How big?) What is the unicity point of a one-time pad? (Chessboard unicity) A transposition code is devised that permutes the letters in each block of 64 letters according to a key that is a fixed permutation used for each of the blocks.
(Perhaps the transposition is constructed by randomly assigning the numbers 1-64 onto the squares of a chessboard, and then reading them out by row.) This transposition cipher will of course not change the frequency distribution of the letters. Find the unicity point for this cipher. Use the data below to the extent that it is helpful. (Entropy values are per-letter values.)
(a) Zero-th order entropy of English = log 26 = 4.7.
(b) First-order (frequency) entropy of English = 4.2.
(c) Entropy of English = 1.2.
(d) Log 26! ≈ 88.
(e) Log 64! ≈ 300.