Codes and Ciphers :: Running Key Cipher

To encrypt a plaintext message using the Vigenère Cipher, one locates the row with the first letter to be encrypted, and the column with the first letter of the keyword. The ciphertext letter is located at the intersection of the row and column. This continues for the entire length of the message.

In a Running Key cipher, the keyword is the text of a predetermined book or passage. For example, if the chossed book was "A Tale of Two Cities" by Charles Dickens, then the keyword would be

It was the best of times, it was the worst of times...

Enciphering and deciphering the message is performed using the exact same method as the Vigenère Cipher.

If the predetermined passage is a string of random letters that is only used once and then discarded, this is similar to a One-time Pad.

• 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