#notesandletters

         Letter Relative frequency as the first letter of an English word:

        The Playfair Cipher is not a cipher I would regularly use, mostly because I don't know it well. I also find it cumbersome and not really worth the work compared to other, more useful ciphers. 

Below are the instructions on how to do it. I didn't write them as this site here does a better job of explaining it than I could.

Table:

                     K E Y W O         R D A B C         F G H  I  J         L M N P S         T U V  X Z

                    If both letters are the same, add an X between them. Encrypt the new pair, re-pair the remining letters and continue.

If the letters appear on the same row of your table, replace them with the letters to their immediate right respectively, wrapping around to the left side of the row if necessary. For example, using the table above, the letter pair GJ would be encoded as HF.

If the letters appear on the same column of your table, replace them with the letters immediately below, wrapping around to the top if necessary. For example, using the table above, the letter pair MD would be encoded as UG.

If the letters are on different rows and columns, replace them with the letters on the same row respectively but at the other pair of corners of the rectangle defined by the original pair. The order is important - the first letter of the pair should be replaced first. For example, using the table above, the letter pair EB would be encoded as WD.

        The Railfence Cipher is a simple scramble code that is fairly easy to break, as even when it's encoded there is still a fairly obvious pattern. But it would be negligent and silly not to know it, so here's how:

 First, write out your message, no spaces.

HELLOWORLD 

Next, arrange these letters so that you can read them as columns, from up to down, left to right.

        H  L  O  O  L

E  L  W  R  D

You can do as many rows as you want, but I just used two. Also, if there are any spaces left by not enough letters, you can either leave blank or substitute X for the emptiness.

Next, you simply read it off as rows, left to right, up to down, to that it looks like this:

HLOOL | ELWRD

                Directions:

Using a code word, write it over the message.

Code word: APPLES

Message: HELLOWORLD

         A|P|P|L|E|S|A|P|P|L

H|E|L|L|O|W|O|R|L|D

Use the two letters you get and encode them with the table, so that:

A+H = H, P+E = T, P+L = A ...

The coded message: "HTAWSOOGAZ" and so on.

To decode, simply put the code word over the coded message, and reverse the process.