| Polybius Square |
Article Index for Polybius |
Website Links For Polybius |
Information AboutPolybius Square |
| CATEGORIES ABOUT POLYBIUS SQUARE | |
| classical ciphers | |
| early telecommunications | |
| steganography | |
|
Basic form In typical form, it appears thus:
Each letter is then represented by its co-ordinates in the grid. Thus "BAT" becomes "12 11 44", for example. Because 26 characters do not quite fit in a nice square, we round down to the next lowest square number by combining two letters - I and J, usually. (Polybius had no such problem because the Greek Alphabet he was using had 24 letters). Alternatively, we could add digits as well and get a 6 × 6 grid. Such a larger grid might also be used for the Cyrillic Alphabet , which has 33 letters. Telegraphy and steganography Polybius did not originally conceive of his device as a cipher so much as an aid to Telegraphy ; he suggested the symbols could be signalled by holding up pairs of sets of Torch es. It has also been used, in the form of the " Knock Code ", to signal messages between cells in Prison s by tapping the numbers on pipes or walls. In this form it is said to have been used by Nihilist prisoners of the Russia n Czar s, and also by America n Prisoners Of War in the Vietnam War . Indeed it can be signalled in many simple ways (flashing lamps, blasts of sound, Drums , Smoke Signal s) and is much easier to learn than more sophisticated codes like the Morse Code . However, it is also somewhat less efficient than the more complex codes. The simple representation also lends itself to Steganography . The figures from one to five can be indicated by Knot s in a string, stitches on a quilt, letters squashed together before a wider space, or many other simple ways. Cryptography 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! 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 Cipher s such as the ADFGVX Cipher , the Nihilist Cipher and the Bifid Cipher . |
|
|