Codes and Ciphers

Caesar Code/Cipher

The Caesar Cipher:

also known as a shift cipher, Caesar's code, or Caesar shift is one of the oldest and most famous ciphers in history. While being deceptively simple, it has been used historically for important secrets and is still popular among puzzlers.

Cipher Description:
The Caesar cipher is named after the legendary Roman emperor Julius Caesar, who used it to protect his military communications. It is a simple substitution cipher, where each letter corresponds to another letter a certain number of positions forward or backward in the alphabet. For example, a shift right of 5 would encode the word Caesar as “hfjxfw”. Due to this simplicity, the Caesar cipher offers little security against those with even a passing knowledge of cryptography.

Example

The easiest way to understand the Caesar cipher is to think of cycling the position of the letters. In a Caesar cipher with a shift of 3, A becomes D, B becomes E, C becomes F, etc. When reaching the end of the alphabet it cycles around, so X becomes A, Y becomes B and Z becomes C.

In this example the phrase “I came, I saw, I conquered” becomes “L FDPH, L VDZ, L FRQTXHUHG” once encoded with a shift of 3.

If you assign numbers to the letter so that A=0, B=1, C=2, etc, the cipher’s encryption and decryption can also be modeled mathematically with the formula: