The Polybius Cipher ------------------- The Polybius Cipher is another type of substitution cipher. It involves using a 5x5 matrix holding all the letters of the alphabet. Yes, so, there are 26 letters in the alphabet and a 5x5 matrix can only hold 25 letters. This is a trivial problem. The least used letters are simply paired up. The best options would probably be x and z, so let's put them together. This will give us the following matrix: | 1 | 2 | 3 | 4 | 5 | -|---|---|---|---|---| 1| a | b | c | d | e | -|---|---|---|---|---| 2| f | g | h | i | j | -|---|---|---|---|---| 3| k | l | m | n | o | -|---|---|---|---|---| 4| p | q | r | s | t | -|---|---|---|---|---| 5| u | v | w | y |x/z| ---------------------- Ok, now that we have our simple 5x5 matrix, we can start the substitution process. For example, the letter 'a' is 1x1 or x=1,y=1. This can be simplified by 11. Another example, let's take the letter 'n'. This is in the position 4x3 or x=4,y=3. This can be simplified to 43. So, now, let's encrypt a simple message. I HATE MY WIFE 42-32-11-54-51-33-45-35-42-12-51 As you can see, I separated the numbers by the symbol '-'. This could be any other symbol or even just a space. Perhaps to confuse and mislead someone, you could use random symbols, just as long as the numbers stay in the correct order or else the message will be misinterpretted. Deciphering the message is as easy as as substituting the numbers into the grid. This will give you the corresponding letter. This is the most simple version. If you wish to secure your messages with someone, jumble up the letters in the grid. As long as the receipient has the exact matrix, they will be able to decipher it. I hope this has been helpful and interesting. invas10n -------- [Ask The Experienced, Not The Learned]