Date: 1914–Present
Location: Worldwide
The Conspirators: Government intelligence agencies
The Victims: Governments who get spied on
Ever since World War I, but most especially during the Cold War when the United States and the Soviet Union were engaged in an arms race and all its accompanying espionage, the airwaves have carried dozens of mysterious radio broadcasts. These broadcasts come over shortwave, a radio frequency band notable for its extreme long distance capability. Each of these mysterious radio programs has certain specific days and times on which it broadcasts. Typically, the broadcasts consist of a spoken voice reading long strings of nonsense letters and numbers. Conspiracy theory hypotheses have abounded for years about what these mysterious radio stations might be, but the leading theory is that they are governments transmitting information to spies located in foreign countries.
In this case, the conspiracy theory is spot on. In at least some cases, stations have been proven to be encrypted communications to spies.
Encrypted transmissions via Morse code began to be widely used during World War I, allowing militaries to communicate over long distances without their broadcasts being understood by the enemy. Over the decades, these encrypted Morse code broadcasts gradually evolved into what we now call a numbers station. It’s now a spoken voice reading off numbers instead of those characters being sent as Morse code, but all work the same way: Important information is encrypted into nonsensical letters or numbers, then transmitted via shortwave radio, and received and decrypted on the other end back into readable text.
During the Cold War, amateur shortwave operators began finding and cataloging these encrypted broadcasts, which they called numbers stations because most of them broadcast long strings of numbers, in groups of five at a time. Nobody knew what they meant, and all of these broadcasts were on unlicensed stations. Amateur investigators used direction-finding technology to try and locate the sources of the numbers stations. Many of them turned out to be broadcast from inside secure military bases.
One popular alternate hypothesis has been that numbers stations are utility broadcasts, which typically include info like weatherfax data (a system for sending satellite pictures of storm fronts) and ice warnings to ships at sea, fishery fax data, oceanographic buoy data, and other such things. But most utility stations send data signals consisting of dots or blanks that come out as visual images on the receiving end, not encrypted strings of spoken numbers. So this hypothesis never seemed to fit very well.
Eventually, a series of high-profile arrests proved the true explanation for number stations:
• In 1989, a Czech spy was arrested in the UK, caught receiving and decoding numbers stations broadcasts from Romania.
• In 1998, five spies called the Cuban Five were arrested in Miami, having received communications for years from a Cuban numbers station nicknamed Atención.
• Nine days after September 11, 2001, in an event that might have been overshadowed by other news, the US Defense Intelligence Agency arrested one of its own senior analysts, who was also found to have been decrypting messages from the Cuban station, Atención.
• In 2009, a retired US State Department official and his wife were arrested in Washington, DC. For years, they had been spying for Cuba, and had received instructions via a Cuban numbers station using a shortwave radio given to them by the Cubans.
• A ring of ten Russian spies headquartered in New York City were arrested by the FBI in 2010, having been caught listening to a numbers station and writing down all the numbers.
• In 2011, a Russian couple was arrested for espionage in Germany, having received information via a Russian numbers station for more than twenty years. Interestingly, they were caught only after upgrading to more modern encrypted satellite communication gear.
So it does appear, after all, that the conspiracy-theory version of numbers stations turns out to be the true one: governments communicating worldwide with spy networks.
Shortwave is used for numbers stations and other services that require a signal to be carried over very great distances, even all the way around the world. While most radio bands have ranges limited to line of sight, shortwave can reflect and refract from the ionosphere, allowing them to propagate as far as needed. If the transmitter is powerful enough, you can rest assured a shortwave signal will get there.
Shortwave also has a number of other important and unique benefits. First, it’s virtually impossible to determine who might be listening to a radio station, and there is no practical way to find an active receiver because they don’t transmit anything back. Compare this to Internet signals, which go through routers and servers and get logged.
This radio band is also immune to massive infrastructure failure, since it doesn’t depend on the Internet, or physical wires, or satellite communications. All you need is a transmitter and a receiver, and a shortwave radio will work very well anywhere in the world. The receivers are widely available worldwide. Anyone can buy one at a thrift or surplus store for very little money, even in underdeveloped nations, and they can even be built relatively easily. They are the ultimate untraceable receiver.
Most numbers stations transmit numbers in blocks of five digits, and the voice usually repeats each block of five once. There can be any number of five-digit blocks, depending on the length of the message. The use of five-digit blocks is simply a convention in encryption. There are any number of encryption schemes out there, but a transmission in groups of five characters is the standard. It makes it easy for the recipient to write them down or type them into a computer. Each block is repeated to minimize transcription errors, and it also helps for times when the signal strength isn’t great. Seeing that the numbers stations transmit in this form gave a very big clue that they were sending some encrypted message.
Some encryption schemes can be decrypted with pen and paper by a recipient who has the key, typically a single-use key called a one-time pad. This is a long string of random text for which the number value of each letter is added to the number value of each letter in the message to be encoded. It is only ever used once, making it impossible for a cracker to find common patterns. While low-tech, a code encrypted with a one-time pad is essentially unbreakable. The downside is that the recipient will need to have some kind of book or list of one-time pads, and that’s evidence that could be used against him. On the other side of things, it’s very easy for the intended recipient who has the correct keys to use computer software to decrypt a message from a numbers station, but again, the presence of this program on a computer is evidence that can be used against the spy. However, such a program can use more advanced encryption like RSA, the modern standard used today that powers web browser encryption and financial transactions.
The question of whether numbers stations are a conspiracy theory that was proven true is a sticky one. While even the most conspiratorial interpretation of them has been proven true, what’s not clear is that a conspiracy theory ever existed before the first spies who used these numbers stations were arrested. Yes, the use of these stations in espionage has been documented since World War I, but this hasn’t always been public information. Newspaper reports of arrests, on the other hand, have freely discussed how the numbers station was employed by the spy and how it constituted evidence against him. So, while it isn’t really appropriate to credit conspiracy theorists for having uncovered this one, we can certainly give them credit for their interpretation being the correct one.