| Basics of the One-Time-Pad |
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| Tuesday, 29 May 2007 | |
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Introduction: Cryptography and Stenography are used in many more places that you may realize, yet is not used as much as it should be in some places. Wether you use these methods in your business, or your home, be sure to use good encryption. Not only does it ward off any onlookers, it will develop good habits in you. The one time pad method was invented by the Russians, er, Soviet Union during the Cold War. It is simple in method, but UNBREAKABLE if used RIGHT. First out, I will start off with what is used in this method: - The one time pad itself. This is a pad of random numbers that has to be at least as long as your message text or longer. If you plan on sending many messages, the best way is to make a longer pad, even if the messages will not be sent often. See, in order for this method to work, BOTH PEOPLE have to have the same exact one time pad. And if you make short pads, the more you will have to trade pads with the message receiver/sender and therefore the more possible ways someone may find the pad (i.e. in a dead drop) or discover that that is the method of encryption you are using. Also, all the numbers MUST be completely random. DO NOT use a computer to generate these number, because computers still tend to follow paths and are not as random as the human mind. -Your message to be encrypted. Remember the message cannot be longer than your pad. The Soviets had pads, all with hundreds of numbers on a sheet, with hundreds of sheets in a pad. -Pencil and paper First, we must change all periods to and "x" In example, "Hello." becomes "Hellox" Also all signs like "$", "&" "@" and such must be also changed to their respective word forms. Also spell out ALL numbers, i.e. ONE THREE SIX NINE, etc. Now for the method. Lets say the following is my Pad of random numbers: 3243 8532 1978 3576 2884 0582 1024 7249 0184 2467 4824 0572 4397 Your one time pad would be longer, but this is all we will need for our first message. One good way to make a one time pad is to take a series of random letters, like "ADHIWURTQMCKOKEZPLWIEUCNAOURSF" and use the key below to convert them into numbers. Split them into groups of four for simplicity. Now we must convert out letters to numbers. And type of key here can be used, but for simplicity lets go with this: A=01 B=02 C=03 D=04 E=05 F=6 G=07 H=08 I=09 J=10 K=11 L=12 M=13 N=14 O=15 P=16 Q=17 R=18 S=19 T=20 U=21 V=22 W=23 X=24 Y=25 Z=26 Simple enough, but it will still be an unbreakable code. Remember to use "01" instead of "1" and so on or your math will not come out right. Now lets create our message, say: "Meet me at Eleven." This message must be formatted like so: "MEET ME AT ELEVENX" When coding the message, end the message with "XX" to signal termination of the message. If needed, add additional X's to 'pad-out', or run out the current 4 digit number string. Now to encrypt the message. First, change the letters to numbers: 13050520 1305 0120 05120522051424 Then format into 4 digit phrases: 1305 0520 1305 0120 0512 0522 0514 2424 Notice I added two X's at the end to signal termination. If this would not have come out even, I would have just added more. Now to encode the message. The numbers are added with Fibonacci Addition. Numbers ARE NOT carried over to the next column. I.E. 92+71=63. You add left to right this way. Notice the first group of four numbers is not used to encode the message. This is the start key, and when the message is received the person can tell by this un- changed number where in his pad the message starts. So lets encode our string. First is the pad numbers, then the message numbers. (I chopped off the un-needed numbers from our pad example.) One time pad: 3243 8532 1978 3576 2884 0582 1024 7249 0184 Message: ---- 1305 0520 1305 0120 0512 0522 0514 2424 Result: 3243 9837 1498 4871 2904 0094 1546 7753 2598 Tada! You know have your encrypted message. Now the Soviets went a step further, and changed the above numbers to letters again with a old radio number code at the time I believe (correct me if I am wrong). That is not needed but again adds a bit of security. To decrypt the message, do the same method but BACKWARD, using Fibonacci Subtraction. If you come upon two numbers which would equal a negative, add ten to the first number, i.e. 4-9 = (10+4)-9 = 14-9 = 5. : 3243 9837 1498 4871 2904 0094 1546 7753 2598 3243 8532 1978 3576 2884 0582 1024 7249 0184 ------ 1305 0520 1305 0120 0512 0522 0514 2424
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