This is something some of you might find familiar because it is shown in the movie: National treasure
I choose Playfair as my keyword, but Playfair has two a's in it, and I can only use each letter one time. So I remove the last a. So it says "PlayFir"
Now I write the rest of the alphabet without repeating myself. So my keyword is playfir, so I can't use the letters p, l, a, y, f, i, r anymore. For understanding see next page
So as you can see I wrote the rest of the alphabet, but didn't use the same letters again, so basically you write the whole alphabet but without using the same letters.
Now I want to encode a sentence or a "word".. I'll encode "Cipher"
I need to split the word "Cipher" into pairs. So CI - PH - ER.
Now I need to find CI in the matrix.
So now I've found CI. Now I need to encode CI. To encode CI I need to find out which letters are in their right side.
So the right side of C is D and the right side of I is R. So we've encoded CI to DR.
Now we need to encode PH.
You need to make a box around two letters if they have ONE row or more separating the two letters. As in the next example
You now have a box around PH and not a row like CI. So now you need to take the letters you want to encode and swap it with the ones in the opposite end og the rectangle.
So P becomes A and H becomes E. You can only choose the corners inside the your box.
So far we have: DRAE. Now we need to encode ER
To encode ER. We do the same as previous. We create a box around them, and choose the letter in the right/left corner. Opposite from the letter we want to encode.
So basically we have ER encoded to GI. So e becomes G and R becomes I.
So now we have DRAEKGI! And if we want to decode it, it becomes Cipher. To decode you do the opposite.
There is still some basic rules I haven't covered yet, so if you think you understand this fully, you don't need to read the rest.
Now I want to encode two random letters, just to show you guys the rest of the rules. I want to encode B and D. But there is no column to encode D.
So we need to wrap it around
So we copied the first column and pasted it so it also becomes the last, so we can decode D.
So now we move the letter to the right so B and D becomes C and I
Now if we have two letters in the same column, we swap the letter with the one DOWN below it.
So we want to encode GO. To encode we need to go DOWN. So G becomes O even though it is one of the letters we want to encode. So O becomes V.
So GO becomes OV.
NOTE: when you encode and decode you need to ignore all spaces and figure out the sentence yourself. Separate all duplicated letters with X. Like hello world becomes: helxo world
I hope you understood my long guide. I made a encoded sentence on the next page, so feel free to solve it. The keyword is still playfir. - twitter:@neklasd
DECODE THIS! To decode just do the opposite!