Codes and Ciphers :: Keyword Cipher

The Keyword cipher is identical to the Caesar Cipher with the exception that the substitution alphabet used can be represented with a keyword.

To create a substitution alphabet from a keyword, you first write down the alphabet. Below this you write down the keyword (omitting duplicate letters) followed by the remaining unused letters of the alphabet.

ABCDEFGHIJKLMNOPQRSTUVWXYZ
KEYWORDABCFGHIJLMNPQSTUVXZ

To encipher a plaintext message, you convert all letters from the top row to their correspondng letter on the bottom row (A to K, B to E, etc).

These types of simple substitution ciphers can be easily cracked by using frequency analysis and some educated guessing.

• Monoalphabetic Cipher
• Caesar Cipher
• Atbash Cipher
• Keyword Cipher
• Pigpen / Masonic Cipher
• Polybius Square
• Polyalphabetic Cipher
• Vigenère Cipher
• Beaufort Cipher
• Autokey Cipher
• Running Key Cipher

• Transposition Ciphers
• Rail Fence
• Route Cipher
• Columnar Transposition
• Polygraphic Substitution
• Playfair Cipher
• Bifid Cipher
• Trifid Cipher
• Four-square cipher

• Other Ciphers and Codes
• Book Cipher
• Beale Cipher
• Morse Code
• Tap Code
• One-time Pad
• Scytale
• Semaphore
• ASCII
• Steganography
• Techniques
• Frequency Analysis