transposition cipher

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transposition cipher A cipher, or a component of a more complicated cipher, that involves the symbol at each place in the plaintext being moved to a newly decided (and often different) place, i.e. within each block of plaintext the positional indices of the symbol places are changed according to some plan. Since a cipher must be invertible (for decryption), the plan must be a permutation of the range of positional indices. Compare substitution cipher.

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