Make a pattern of alphabets. In addition, you need a code word which should be preserved only in your memory. It should be as long as possible and be kept strictly secret. You should also change it from time to time.
For example, take a code word like ACCOMPLICE. If the message you want to send is MEET ME AT JOE'S CAVE, then write the code word under the message again and again: MEET ME AT JOE'S CAVE ACCO MP LI CEA C COMP From every vertical pair of letters in the original message and the code word, make a single letter by using the pattern. The first pair is MA. Find the text letter "M" in the left column, and follow this horizontal row until you arrive at the vertical column under the code word letter "A". In this case, you find the letter N in the horizontal column. EC gives you H, and so on. The coded message will read: Nhhi zu me mtfv cpoyz.
Without knowing the code word, it is almost impossible to decipher this code, for it conceals the frequency with which certain letters are repeated. To decode the message, write the code word under the coded message. Look up the letter of the code word in the left-hand column, then follow the horizontal row to the letter of the coded message. The letter above this vertical column will be the letter of the original message.
Writing with a Stencil
With the help of a stencil you can encode a message which can be written and read very quickly. Cut a stencil of thin cardboard exactly according to the design shown in the illustration below. Lay the stencil on a piece of paper so that the figure 1 is in the upper left-hand corner. Then start writing your message in the openings, one letter per hole. When all the holes are filled, turn the stencil so that 2 are at the top. Continue the same way with 3 and 4. Fill all the remaining holes at the end of the message with some meaningless letter such as X to make it harder for an outsider to decode.
Shifting alphabets the secret of this code is in shifting two alphabets.
1. ABCDEFGHIJKLMNOPQRSTUVWXYZ message letters
2. BCDEFGHIJKLMNOPQRSTUVWXYZA code letters
Take the code letter under the message letter in the first alphabet. For example, HURRY UP becomes IVSSZ VQ. The code can be varied by shifting the second alphabet a different number of letters.
Code Box
Divide the alphabet into nine groups and number them, starting in the upper left-hand corner. ABC=1, MNO=5, VWX=8, etc. In each group the letters are numbered 1 to 3. In this way, each letter of the alphabet is designated with two numbers. In the empty spot in box 9 you can add an 'e' the letter which occurs most frequently in English. Thus, you can use either 22 or 93 for e, thereby making it more difficult for outsiders to break the code. O, for example, is the third letter in box 5. Therefore 53=0. In this code, BEWITCHED becomes: 12,22,82,33,72,13,32,93,21, or, more simply, 1222823372133293-21. For a variation, instead of numbering each group of letters in a box from 1 to 3, number them continuously. In this code, s is 7,19, for the 7th box and the 19th letter. Then SALT would be 7,19-1,1-4,12-7,20.
