Polybius Square - Cryptography

Cryptography

The Polybius cipher can be used with a keyword like the Playfair cipher. By itself the Polybius square is not terribly secure, even if used with a mixed alphabet. The pairs of digits, taken together, just form a simple substitution in which the symbols happen to be pairs of digits. In this sense it is just another encoding which can be cracked with simple frequency analysis. However a Polybius square offers the possibility of fractionation, leading toward Claude E. Shannon's confusion and diffusion. As such, it is a useful component in several ciphers such as the ADFGVX cipher, the Nihilist cipher, and the bifid cipher.

Polybius was responsible for a useful tool in telegraphy which allowed letters to be easily signaled using a numerical system. This idea also lends itself to cryptographic manipulation and steganography.