When I was growing up, my father was into cryptography – codes and codebreaking. I’m not an expert, but I picked up a lot of minor crap that’s occasionally been useful.
The other day a friend of mine tried to use what I call a keyboard shift. It’s a simple letter substitution code, but it trips a surprising number of people. If you’re a touch typist it’s easy – move your fingers off the home keys. For example, by moving my fingers right one space, my name becomes Lotl D[rmvrt. That can be made a bit less obvious by wrapping when you do a symbol. So: Lotl Dqomvrt.
Substitution codes work fine for easy encryption. And when the message is very short it’s difficult to break. For longer use, however, they’re just not very good.
The best encryption (outside computer encryption – I’m going to skip them for this post) is a one time pad. That’s a booklet with a bunch of code words replacing words you use frequently plus some other bits and pieces. You’ve got one, your code recipient has one. The big thing is once you’ve used it, you destroy it. One time, done. A lot of militaries use something similar, except there are a lot of copies and they get used for a period of time rather than one time only.
The second best I’ve found is the Massive Tome. (Not the right phrase, but it works very well.) You and the other person use a book – same edition, preferably HUGE, and ideally something that simultaneously isn’t likely to be in many hands but for which your possession isn’t odd enough to cause questions. A Bible has been a frequent choice – while Bibles are everywhere, the odds they have one Exactly Like Yours is surprisingly unlikely. This is especially true if you go out of your way to have a different one.
The way it works is every word you send is three numbers. The numbers are page, line, and word on that line. It’s pretty obviously a code, but cracking it is surprisingly challenging. And yes, that includes using computers. That’s because if you use it wisely you try very hard not to use the same page/line/word number combination more than once. Thus it comes close to being a one time pad. Of course, if you’re using it around Bad Guys, they’re eventually going to look through your possessions to see what books you have. Then it’s just a matter of matching the intercepted message till they find your book. Still, in the matter of encryption it’s nearly brilliant.
The secret message type that always fascinated me was steganography. Though often thought of as a type of encryption, it isn’t. It’s instead a means of hiding the actual message. It can be combined with encryption, of course. One of the earliest types known was to scratch the message into a backer board before pouring wax over it. That’s when wax tablets were used as temporary writing slates. (Done from early Greek/Roman times, still in use in the late medieval times. In fact some places it’s still in use.) Some other things you may happen to recognize are to make a pattern of words in a letter – say, every tenth word, or the third word after (or before) a period. (No, there’s no steganography in this message. Don’t bother looking.) “Paul is Dead” is a classic – the message is there, but you have to play the record backward to hear it.
No, there’s not really a point to this post. I just had a couple of things happen recently that reminded me of the fact my dad and I used to write, detect and break secret messages just for the fun of it, and I thought I’d share some of the ones that aren’t ‘only usable with massive computer cycles’.