Obscure "Numbers Stations" Relay Cryptic Messages

It was just after Christmas, 1990 as I tuned around the shortwave dial of my new radio; I heard a few interesting things...a Chinese-to-English language course, a British newscast, The National Institute of Standards and Technology's "tick-tock" of the clock, and a few doomsday prophets who were screaming demands for souls and money. But, with a few turns of the dial I heard something else -- a succession of numbers/letters, recited by a female automated voice. It sounded like something you'd hear if you dialed a wrong phone number, or maybe even something out of a sci-fi flick. It was my introduction to the strange and mysterious world of "numbers stations".

Between the approximate range of 2.3 MHz to 30.0 MHz of the shortwave band, a plethora of signals and transmissions can be heard. As opposed to ground-based radio transmissions, shortwave's high-frequency radio waves are bounced off the ionosphere and follow the curvature of the Earth, allowing for signals to reach extremely long distances, especially at night. Browse around a while and you may be surprised what you encounter.

Numbers stations are said to have been around as early as World War II, reaching their height during the Cold War and leveling off since the late 1990s to a lesser, yet steady stream of broadcasts ever since, with the most recent and noteworthy activity in the former Soviet-Union, Europe, Cuba and North/South America. Very few have ever been explained, leaving speculation open to a range of conspiracy theories, from drug trafficking to terrorist agendas. Most evidence about the utility of the stations, however, pointed to government-sponsored intelligence agencies who were sending encrypted messages and operational instructions to their agents on covert assiginments abroad, or "spies", to put it simply.

While countless inquiries and investigations have been conducted by government agencies and radio aficionados alike, only two such entities have confirmed such operations: the Polish Institute of National Remembrance and Czech Foreign Intelligence. No rhyme or reason has been cited as to why the stations exist, and 70 years later we're no closer to any definitive answers. Who has made it priority to run these broadcasts for so long, and why? Are all of these encrypted messages transmitting sensitive government intelligence or are they smokescreens for more nefarious intentions? How are these stations allowed to interfere with legitimate radio broadcasts, air traffic control and marine radio with impunity? Most people however are probably asking this question: What exactly are "numbers stations"?

In the arena of encrypted broadcasts, there are three different types of transmissions: digital station transmissions, which employ various types of digital tones to convey encrypted messages; the more widely known method of Morse code transmissions' and numbers stations.

Numbers stations transmit in various different languages and voices. These voices are male, female (sometimes children) and can either be recording samples of live reads or electronicially generated. Some recitals are monotonous and grim, while others are playful and enthusiastic. ENIGMA 2000, a UK based online group who monitor and gather information on numbers stations, catagorize the broadcasts by their language and given nicknames. Some station's names are coined after their signature introduction phrases, as the Cuban "Atencion" station. Other station's names are derived from pieces of music that are featured during their broadcasts like the (English folk song) "Lincolnshire Poacher" or "Swedish rhapsody" which features a young girl reciting numbers over a glockenspiel tune. Many stations are simply named for the respective language (e.g. "Bulgarian Betty"). The audio oddities and erie sound effects in these broadcasts run the gamut from buzzers and church bells, to simulated horse gallops and slide-whistles. Recordings such as these can be heard on the Irdial Discs release The Conet Project.[[{"fid":"8473","view_mode":"default","fields":{"format":"default"},"type":"media","attributes":{}}]]

The radio transmissions often broadcast at the top or bottom of any given hour, usually beginning with digital tones or distinctive musical recordings to alert the recipient and allow them to prepare to begin encoding. An announcing start will then inform the recipient of the amount of 4-5 digit number groups or letters contained within the message, followed by the message itself (sometimes repeated), which then concludes with a sign-off in the station's native language and/or signature tones or music. While many stations often use similar broadcast structures as the aforementioned, there is, at times a multitude of distinguishing characteristics which make each station unique.

Some broadcasts occur every day at a fixed time, then disappear soon after, while other stations have irregular schedules and transmit sporadically over a period of time.

What makes these broadcasts so difficult to understand or decipher? The first factor is that the messages are composed using cryptographic algorithms where plaintext is combined with a random key, in effect creating a mathematically unbreakable encryption. The groups appear to be totally random and without any logical order or meaning. These numbers or letters (in the phonetic alphabet) are actually "one-time-pad" encrypted messages. Two keys are constructed -- one for the broadcaster, one for the recipient. This key is generated with the intention of being used once and then discarted. With some basic calculations and a pen and paper, the message is deciphered and comes to fruition. If this sounds confusing, just imagine a more elaborate version of the Little Orphan Annie decoder rings from the movie A Christmas Story.

The second layer of security lies in the fact that these broadcasts are anonymous, untraceable one-way communications. The intended recipient could be anywhere in the world and needs nothing more than a shortwave radio, the frequency and time of the broadcast and his or her one-time pad. There is no IP address to spoof, no traceable phonecalls or emails. The method is foolproof and your secrets are safe -- short of being caught in the act...

In 1998, the US government arrested five intelligence officers from the Cuban Wasp Network, who later became known as the Cuban Five, for conspiracy to commit espionage, conspiracy to commit murder and acting as agents of a foreign government. Among the FBI's evidence against them was their decryption program used to recieve messages via shortwave radio.

Ana Belan Montes, a Cuban spy who had been passing secrets to Cuba for more than 20 years and worked for the U.S. Defense Intelligence Agency was ultimately convicted of espionage in 2002. A small shortwave radio and a deciphering pad were among the incriminating items. 

In the 2010 court papers alleged the Russian spy ring, which included the infamous "sexy spy" Anna Chapman, used "coded radio transmissions and encrypted data", and most recently in 2011, a couple from west Germany were actually caught decoding encrypted shortwave transmissions as Special Forces executed a raid on their home.

While no confirmation of the utilization of numbers stations by U.S. government agencies (domestic or abroad) has been made, there have been reports of stations allegedly operating out of Virgina and foreign embassies in Washington, D.C. A former naval intelligence officer reportedly discovered transmissions broadcasting out of Florida’s West Palm Beach airport just over a decade ago. On an NPR segment entitled Lost And Found Sound, John Winston, the FCC's assistant chief of the enforcement bureau was asked about these findings and responded, "We don't intend to discuss these stations, if any exist at all. I'm not saying there are, even if your scientists say there are stations that are transmitting in this country."

Routinely scanning the shortwave dial, one will more than likely run into a numbers station transmission. Whether you'll be hearing the encrypted orders for a military strike or the coordinates of a rendezvous point for a criminal enterprise, it's anyone's guess. It's the allure of the unknown, the unseen which has kept many shortwave hobbyists tuning in for the past few decades. As long as human nature compels some to hide, so too will it move others to seek. 

...end of message.