I was going through the older episodes of Skeptoid, one of my favorite podcasts, when I listened to one on Numbers Stations. These are mysterious shortwave radio transmissions that usually consist of an automated voice reading off sequences of apparently random numbers. The most rational explanation for these stations is that they are secret government communications to spies or saboteurs using something called a one-time pad, something else I hadn't heard much about before.
It's a method of encryption so good that it's thought that no one can break it without the key, even if you had infinite computing power. The reason for that is the numbers in the broadcast give no information (or clues) that can be used to decipher it--the only real vulnerability is that someone finds the key. This explains the "one-time pad" part of it--like in so many spy movies, the key is destroyed after its one-time use. I still have to wonder, though--COME ON! Maybe I'm just a hopeless child of 80s optimism and faith in human ingenuity or whatever, but I'm sure a true genius could learn how to crack these codes. What do you think?
My dad has always been a fan of shortwave radio, and I had a great time playing with them when I was a kid. I'd usually tune it to hear propaganda broadcasts from China and such (this was at a time when our relations with them was much worse than they are now). I even mailed Radio Beijing once and asked for some info about the country; they sent me a small white booklet called "Human Rights in China" that I wish I had kept. I remember it had a chapter about the allegations that Chinese parents murdered their daughters if they preferred a son, since they were only allowed to have a single child. Anyway, the booklet first stated that no such infanticides had ever happened and was just a lie made up by hostile governments. Later on in the booklet, though, it said the Chinese government had gotten much better at cracking down on it, and gave some statistics to show how much it had decreased. Even back then I was able to spot the inconsistency.
But anyway, I digress. I also heard many of these number stations, as well as plenty of others that were obviously radio modems. I was always fascinated by them and would have loved to find some way to figure out what they were saying. It's pretty amazing to think that we're right now surrounded by all kinds of top secret signals that none of us will ever be able to decipher.
On a related note, I also enjoyed Brian's episode on The Missing Cosmonauts, which concerns two hobbyists who made extensive records of Soviet satellite and other transmissions from space during the Cold War. They made some recordings that are, by the way, extremely creepy and disturbing, of what sounds like doomed cosmonauts dying in space. However, there are no official records to confirm that these missions ever took place, but of course the infamous Soviet secrecy and misinformation campaigns cast everything into doubt. Brian is skeptical that the recordings prove what they claim, but it's not clear in any case what the recordings are actually recordings of, if that makes any sense.
At any rate, give a listen to both of them! They have sound samples of the material in question and are quite fascinating.