A classification scheme for ciphers* Gary Knight - Cryptanalysts Corner, Cryptologia 1 (January 1978):68--74.

• Substitution

  • Polyalphabetic
    • Periodic
      • Non-Interrelated Alphabets
      • Interrelated Alphabets
      • Pseudorandom Key
    • Non-periodic
    • Non-Random Key / Random Key*
  • Polygraphic
    • Digraphic, Algebraic
  • Monoalphabetic
    • Standard, Mixed Alphabet, Homomorphic,
    • Incomplete Mixed Alphabet, Multiplex, Double
  • Fractionating
  • Bifid, Trifid, Fractionated Morse, Morbit

• Transposition

  • Geometrical - Rail-fence, Route, Grille
  • Columnar
    • Complete - Cadenus, Nihilist
    • Incomplete - Myskowski, Amsco
  • Double - U.S. Army Transposition Cipher

• *=unbreakable

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