I have to give more credit to The Reverend for telling me about numbers stations[wiki] some months ago, but recently they have been moving from the airwaves to VoIP telephone numbers.
For decades, intelligence agencies have been sending secret messages to their agents in the field using shortwave numbers stations broadcasting encrypted messages for all to hear and puzzle over. Now someone is putting numbers stations on VoIP telephone numbers for anyone to call, and posting messages to Craigslist to alert the recipients to the existence of their messages. One of them went up last month and now a second one has appeared. Will there be a third? Who’s behind them? And can you crack the code? [slashdot]
They’re very strange to listen to, and this method of sending secret messages is as old as wireless communication has been in existance. I plan on using this as a topic in an upcoming episode of the podcast. You’ll be able to hear examples of numbers stations there.
For quality numbers station stuff, be sure to check out Seism. http://www.archive.org/details/seism He’s been grabbing numbers stations broadcasts off shortwave and posting them on the Internet Archive. There’s also the Conet Project (sampled in Wilco’s Yankee Hotel Foxtrot) http://www.archive.org/details/ird059
The article you initially sent me seemed to miscommunicate the way number station codes work. It starts with a basic message, let’s say “Hi.” In alphanumerics (A=1, B=2…) this message would be “8 9.” Converting it back and forth is cake (especially for longer messages since patterns emerge & etc.) Now you want to send it in such a way that nothing can stop the recipient from receiving the message (short of the capture and murder of the recipient). So you broadcast it via shortwave (or now phone). Anyone with a radio can hear it and there’s no way to stop the message from getting out. However, anyone can hear it so you need to disguise it. You need a random element that only you and the recipient know. And this is where the genius of numbers stations lies.
Our message is “Hi,” “8 9.” Now we’ll take an infinitely long, non-repeating string of numbers-Pi-3.14… We’ll start after the decimal point. Here’s how numbers stations work:
original: 8 9
randomizer: 3.1 4 . . . . . .
sent message: 9 13 . . . . . .
So the message that gets broadcast would be “9 13” or “I M” oddly enough. The key (no pun intended) to the whole process is the randomizer. It doesn’t make every H=9 instead of 8, it only makes that first H=9 instead of 8. The next time a 9 comes up in the message it could mean anything. And anything could be used to create the random string-a math formula, a specially arranged deck of cards, a specific passage from a book. As long as the sender and recipient are agreed on what the randomizer will be, they can send messages back and forth without anyone ever hoping to crack it.
And the reason it’s uncrackable (no number station’s been cracked, ever, though there is an ongoing project to break one) is because it has two random elements-the randomizer and the initial message. Yes, language does tend to fall into certain patterns over a long enough span, but it is also faily chaotic. So you have an initial message that you don’t know altered by a random string of characters that you also don’t know and each character in the message you have is independent of every other character in the message.
It’s really neat stuff. And if you want a dramatic depiction of it, check out the movie Enigma. It’s all about the code breakers at Bletchy Park in WWII and is really good. There’s also Neal Stephenson’s Cryptonomicon of which a portion focuses on code breaking and making, but I didn’t really like the book even though it’s well-loved and highly-esteemed by the geek community.
So, yeah, I’m a geek. Here’s weird for you. A topic that arose on the Jandek discussion list was all about whether Jandek’s music might be a strange form of military communication a la numbers stations. The argument went that his lyrics and syncopation were actually communicating something else.