______ ciphers move letters around within a message but characters are not substituted.

• A. Transposition
• B. Substitution
• C. Both A and B
• D. Neither A nor B

Answer: (A)

Transposition ciphers rearrange the order of characters in the plaintext without changing the characters themselves. In these ciphers, letters are moved around so the ciphertext contains the same letters, merely in a different sequence. Substitution ciphers, on the other hand, replace each letter with a different one, so the characters themselves change. Since the question emphasizes moving letters but not substituting them, it describes a transposition. Classic examples include rail fence and columnar transposition methods. Some systems mix both techniques, but the essential action here is rearrangement, not substitution.