Codes and Ciphers :: Caesar Cipher

A Caesar cipher is one of the simplest (and easiest cracked) encryption methods. It is a Substitution Cipher that involves replacing each letter of the secret message with a different letter of the alphabet which is a fixed number of positions further in the alphabet.

Because each letter in the message has a direct translation to another letter, frequency analysis can be used to decipher the message. For example, the letter E is the most commonly used letter in the English language. Thus, if the most common letter in a secret message is K, it is likely that K represents E. Additionally, common word endings such as ING, LY, and ES also give clues.

A brute-force approach of trying all 25 possible combinations would also work to decipher the message.

In this example, each letter in the plaintext message has been shifted 3 letters down in the alphabet.

• 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