Number Stations

by Radio Officer Sandro VIALE

NUMBERS STATIONS

A numbers station is a radio station that transmits only sequences of numbers through short waves. Due to the intrinsic shortwave features, the origin of these radio transmissions is unknown, as  the meaning and the purpose of the broadcasts themselves.

The format of messages transmitted by the numbers station varies from station to station, and this has allowed fans to rate them and attribute names to them.
The most popular number stations communicate in English, Spanish, German and Russian, but also French and Oriental languages such as Chinese and Korean.
Most often it is a sequence of numbers, but it is not unusual to hear letters or morse code messages, as well as seemingly random noises and tones.
Often such communications are preceded and / or followed by identifiers indicating the beginning and / or the end of the transmission and other more or less known data. For example, some numbers stations start  with the word “Attention” or similar words, while others precede the number sequence from a music.
In some cases, the transmission starts with the number of numeric groups that will contain the actual message, while in other cases these numbers and letters appear without any significance.

The voices that send these code messages are often synthesized, but there are known cases of live microphone communications.
There is even a radio, called “The Swedish Rhapsody,” which uses the voice of a little girl.

THE BUZZER STATION (UVB-76)

An emblematic example of live voice is the number station called “The Buzzer”. Activated since 1982, it has never interrupted the broadcast unless on three occasions and for short periods. However, the actual communications occur very rarely, with the latest communication dating back to 2010, preceded by another in 2006, for a total of 7 communications or little more in 20 years, according to most of the listeners. For the rest of the time, the station is not switched off, but continues to transmit an annoying electronic noise, which is the source of the station name (“The Buzzer”).
The peculiarity of this number station is that messages are transmitted from the voice of a real person speaking trough a  microphone. It seems that during the long periods of silent activity (or it would be better to say noisy) the microphone is always on, so much so that it has heard noises and conversations in the background.
When transmitted, messages consist of a series of personally identifiable names and apparently random numbers, pronounced in Russian.

Old site of BUZZER UVB-76

Another example is the station called “Backward Music Station” because of the noise it transmits, similar to a disc played in the opposite. The apparent signal is similar to a random noise, but in reality this hides a second signal visible through a spectrograph, similar to an encrypted morse code.

The The Conet Project site collects 150 entries of different number stations, which you can hear through the player at the top right of the web page. The site also collects various information about number stations  which I strongly recommend to read.

WHAT ARE THESE NUMBERS AND WHAT IS THE PURPOSE OF NUMBERS STATION?

The most credited theory is that behind the numbers station there are secret government organizations that use the short waves  band to communicate with agents deployed in various parts of the world.
If this theory were true, the use of short waves would be justified by their ability to reach very distant places, in addition to the difficulty of accurately locating the source signal.
The greatest advantage of such an old technology compared to the most modern communication systems such as the Internet and mobile phones is that radio communication does not contain any reference to the recipient of the message, so it is true that anyone can receive and listen to it without any special problems.
Indeed, the most modern and cutting-edge technologies would in itself bring suspicions to the spy that carries these equipment. If we add that the most common media such as cell phones and e-mails are under governments control, even if these messages were never deciphered by enemies, the only way of receiving them could mean the torture or death of the spy. Moreover, internet and cellular phones and similar technologies are not always available in remote places such as forests and desert areas.
On the contrary  a radio broadcast can be captured by any radios, and the undercover agent can receive the communication in a secure way a radio while is in reception cannot be intercepted or it is very difficult to do so. And even if that were true, a public communication, there will be hundreds if not thousands of people who will receive it. How can an enemy government understand which of these individuals are simple curious radio amateurs, and who are the undercover agents to which the encrypted message is addressed?
The fact that the number stations do not  diminish suggests that some of these stations may be run by terrorist groups and traffickers of various kinds.

If in some cases there have been events that have confirmed the presence of secret government agencies behind the numbers station, this fact does not say it is true for all number stations.

The only case certainly concerns the Cuban station “Atencion!”,  so named because the beginning of each communication was preceded by this word. On some occasions the Havana official station interfered with the signal from the above-mentioned station, revealing its location.
In addition, in a process in which U.S. accused the Cubans of espionage, the United States brought to evidence that they had stolen to a Cuban spy the software to decrypt some of the messages transmitted by the Atencion radio which allowed them to get clear communications. The Americans, to try what has just been  said, led to the process some of these sentences, which were decrypted as an example. On the internet, all you can find are the three phrases in English, and there is no mention of the original encrypted message, or whether these phrases were already in English or translated by the Cuban to make them understandable to the jury. As if it were not enough, we talk about a stolen computer that allowed Americans to decipher those messages, but it is not specified whether this computer was brought up as proof to prove the truthfulness of what they claimed. However, there is no access to the official papers of the process, probably the secret cards  contain relevant details, but without being able to consult, we can at least have some doubts about the affidability of this affair.

THE CIFRARY OF VERNAM

But how would the Americans decipher the messages from the Cuban station “Atencion!”? If communications are made through ether and can be heard by anyone with equipment of a few tens of euros, how is that the only documented case of a presumed success in decrypting these series of seemingly random numbers?

In fact, the first thing that comes to mind is the lack of security in transmitting encrypted messages that everyone can receive. If it is true that the Americans would be able to decipher the Cuban messages through a key stolen from an enemy spy, if you are taken by enthusiasm, might think of buying a radio that receives short waves, transcribes numbers, and, conversely of the CIA you have no decryption key in your hands, take advantage of the computing power of modern computers to try a brute-force attack through random keys generated by the PC  so that the right key will not come out that will allow you to decode the message.
After all, all encryption systems can be decrypted, you continue to tell yourself, in the worst case you try all the available key combinations until you find the right one. Often then an encrypted message contains suggestions about the decryption key: repeating digits or letters, similar pattern messages, patterns repeated in the various encrypted messages.

Well,  sorry to drop you but the encryption system used by the numbers station is no exception. Nowadays it is the only encryption algorithm that cannot be decrypted, as it was mathematically proof.

Detailed clip about a number station reception well masked before going on the air