Doug Bolden's Super-Simple, Super-Easy Autokey Tool!
The Whosiwhasits
What follows (in the next section) is my super-easy, super-simple autokey cipher tool. An autokey cipher is one in which the message itself is used as part of the encryption. The method used below works like this: you take the letters a to z and give them the values of 0 to 25. You discard all the other bits (punctuation, spaces) as flak. You then take your initial phrase, plus a keyphrase. You start out adding the keyphrase to the initial phrase, and when the keyphrase runs out, you then start adding the phrase back to itself. This whole time, you use a modulus of 26 so if you add, say, "P" (with it's value of 15) and "T" (with it's value of 19) you get "I" (with it's value of 8, since it is 19 + 15 = 34 - 26 = 8). It is perfectly acceptable to use a keyphrase longer than the phrase (and is technically more secure in most situations) but it doesn't really work if your keyphrase is of 0 characters.
To give a brief example, let's say your initial phrase is "Hello, how are you" and your keyphrase is "fine". The script below will add "finehellohowareyou" to "hellohowareyou" and generate an outputted, keyed response. According to the program, it is "MMYPVL ZHOYS UOL". The groups of 5 letters is a crypto-classic, and is used in a lot of old ciphers. I retain it here for the fun of it. If it bothers you to read it in such a way, the text box that the result displays in allows you to add and subtract spaces to break the words up.
The value of the autokey system is that you can remember a relatively short keyphrase or keyword, and then still generate a fairly secure message. Not secure in the sense of "If your life depended on it", but secure enough that it takes more time and patience to crack than the vast majority of the kind of day to day stuff you would ever write. Short keys mean you don't have to trade any sort of legend. This means it is less likely that you have to transport two pieces to the code (letting the recipient have both the key and cipher). As long as you can agree on some keys before hand, there you go.
Since there is nothing but characters, you have to spell out quite a bit (numbers, punctuation that is required, and so on), but it's entirely possible.
Anyhow, did this for funsies, mostly, and so that I can use them some on my site.
So, What Are My Keyphrases, Then?
I will use some autokeyed stuff on this site. What are my keyphrases then?
WORK AND SCHOOL RANTS use a single keyphrase, but this is on a need to know basis.
CONTACT INFO uses the keyphrase "contact info". Easily guessed, sure, but not to any sort of random bots.
SPOILER TEXT uses the keyphrase "spoiler text".
PERVERTED THOUGHTS uses the keyphrase "He made love to the fishes". What counts as a PT. I don't know. But I'll let you know when I think it up.
Written by W Doug Bolden
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This work is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License.
The longer, fuller version of this text can be found on my FAQ: "Can I Use Something I Found on the Site?".
"The hidden is greater than the seen."
