Mono-Alphabetic

Use a single substitution alphabet

• With #a elements.

Examples:

• Additive (translation)

  • crypto-symbol = (symbol + key) mod #a.

  • symbol = (crypto-symbol - key) mod #a.

  • Possible keys = #a.

  • Ceasar Cipher (ROT-x).

• With sentence key.

  • Possible keys = #a! -> 26! = 2⁸⁸

Problems

• Reproduce plaintext pattern.

  • Individual characters, diagrams, triagrams, etc.

• Statistical analysis facilities cryptanalysis.

  • "The Gold Bug" by Edgar Alan Poe.