Transposition Cipher
A transposition cipher is a cipher which reorders elements of a plaintext in the ciphertext without adding or removing elements.
- aka permutation cipher
Types
A rail fence cipher is a transposition cipher in which a plaintext’s letters are written diagonally downwards on successive rails of an imaginary fence.
- After reaching the bottom rail, a plaintext’s letters are written diagonally upwards on successive rails until reaching the top rail
- process continues until all of a plaintext’s letters are written on the rails
- The ciphertext is read rail-by-rail from the top rail to the bottom rail
- The key is the number of rails
- aka zigzag cipher
A columnar cipher is a transposition cipher in which a plaintext’s letters are placed in rows of length equal to the cipher’s keyword length and then read in columns to generate the ciphertext.
- alphabetical order of the letters in the cipher’s keyword is the order in which the columns are read