Numbers Stations

Numbers in the Air

Numbers stations are mysterious shortwave radio stations, broadcasting streams of numbers or letters using the phonetic alphabet, by voice, Morse or digital tones. The messages are usually groups of four or five numbers or letters and are typically repeated by reading each group twice or repeating the entire message. These stations are unlicensed high power HF transmitters, broadcasting worldwide in various formats and languages.

They do this day and night on a wide range of frequencies, and it's been going on for decades, yet no single private, commercial or government agency ever stepped forward to officially confirm that they are responsible for these strange broadcasts of numbers. However, today there is enough evidence that intelligence agencies use these numbers stations, also called one-way voice link or OWVL, to send encrypted operational messages and instructions to their agents in covert operations abroad.

The messages are broadcast on very powerful shortwave transmitters with frequencies ranging from 3,000 to 30,000 KHz. The numbers or letters are spoken in many different languages, usually a female voice, but sometimes male or those of children. Many of the broadcasts are mysterious mechanically or electronically generated voices. The stations often use introduction signals as a beacon, prior to an actual message. These repeating phrases, electronic sounds or music enable the receiver to adjust his radio to the desired frequency. In recent years, many numbers stations switched from voice or Morse to digital tones.

Radio amateurs monitor these broadcasts and sometimes give nicknames to a station, according to its typical introduction phrase (e.g. the Cuban "Atención" station), prelude music (Swedish rhapsody) or language of the voice (Bulgarian Betty). Some stations are called counting stations, because of their introduction signal. An example is the Cuban "Atención 1234567890".

The Cold War era, from the 1950s until the end of the 1980s, is known for its numerous and very active numbers stations, not by coincidence the heydays of espionage. Many of the broadcasts came from the Eastern-bloc countries, China and Cuba, but also from several Western countries.

After the 1989 fall of the Berlin Wall, the number of stations significantly decreased from countries like East and West Germany, Yugoslavia, Hungary or Bulgaria. The voices of those stations were mostly Russian or German. However, several decades after the end of the Cold War, stations remain active in the former Soviet-Union, Europe, and in North and South America, and new stations continue to appear all over the world.

Most numbers stations use a basic format to send the streams of numbers or letters. Some stations broadcast every day at a fixed hour and disappear after a few days or weeks. Other stations have an irregular time schedules and appear and disappear over time. One of the most regular numbers stations ever was the Lincolnshire Poacher (E3 Voice), named after the English folk song that was used as its interval signal. After transmitting the very recognizable melody and a call-sign for about ten minutes, the message was sent by an electronic English-accented female voice in groups of five figures.

The station aired every day from the 1970s until 2008. A simple small shortwave radio was sufficient to capture the Lincolnshire Poacher. It is believed that the station broadcast from the RAF Akrotiri basis in Cyprus and operated by the British Secret Intelligence Service. Unfortunately, the world of radio waves lost a true Cold War icon when the station went off-air in 2008. Its Asian sister station Cherry Ripe however is still active.

Why Numbers Stations Top

Although no government or legal broadcaster ever acknowledged any involvement in these broadcasts, it is obvious that the costs and organization of such large-scale illegal broadcasts can only be supported and approved by government agencies. Countries like Russia, China and the United States exploit large shortwave antenna parks in their own country and at their embassies abroad.

The content of the messages appears to be a random series of numbers without any logical order or meaning. It is confirmed in several uncovered spy cases that these seemingly random numbers are actually one-time-pad encrypted messages. Numbers messages were used extensively during the Second World War. The British Special Operations Executive (SOE), the American Office of Strategic Services (OSS) and many other wartime intelligence agencies used them to communicate with their espionage and sabotage teams, operating behind enemy lines.

History has proven this to be a most secure method. One-time pads are sheets or booklets with keys that consist of series of truly random numbers or letters. Enciphering and deciphering a message only requires pencil and paper and some basic calculations. Each message is enciphered with a unique one-time pad which is destroyed after one-time use. If properly applied, one-time pad is the only system that is proven to be mathematically unbreakable. More information is found at the one-time pad page.

The one-way shortwave broadcast has many advantages for intelligence agencies. Powerful shortwave transmitters reflect their signal many times between the earth's surface and the ionosphere, carrying them over very long distances. This enables intelligence agencies to send messages to agents located in faraway countries. The many reflections also make it difficult to accurately locate the transmitter and find out who is broadcasting. The enormous, almost global range of shortwave makes it impossible to identify the country of destination, let alone the person who receives the message.

Therefore, there is little risk of exposing the secret agent who receives a message. A simple commercial shortwave world-receiver can pick up a message and the agent doesn't need a compromising special receiver or crypto equipment. He can easily carry and hide a large number of one-time pads in small booklets or on microfilm, and the manual one-time pad system, although slow and elaborate, requires nothing more than a pencil and paper. Therefore, numbers stations are an ideal method of covert one-way communication to illegal agents abroad.

Evidence for use as Spy Stations Top

Over time, declassified documents from court trials and intelligence agencies revealed the truth about these mysterious numbers stations. They also show that the era of spy stations and espionage is far from over. This information enables us to discard all stories about numbers stations being so-called weather buoys, shipping reports or other fairy tales. Several spies have been caught in possession of shortwave radios and one time pads. Given the widespread and frequent use of numbers stations, the published cases are undoubtedly only the tip of the iceberg.

In 1962, Soviet GRU Colonel Oleg Penkovsky was arrested by the KGB and charged with espionage. During a search of his Moscow apartment, the KGB found one-time pads, instructions on how to receive and decipher encrypted radio messages, including a letter-to-digit checkerboard and a Morse cut numbers table, a shortwave radio, a Minox camera and other spy equipment, cleverly hidden inside a secret compartment in his desk.

Soviet diplomat Aleksandr Dmitrievich Ogorodnik (codename TRIGON and TRIANON) was recruited by the CIA in 1970. The one-time pad, shown on the right, was used by Ogorodnik to decrypt messages, broadcast by the CIA from West Germany. More information on Penkovski and Ogorodnik at the webpage of Andrei Sinelnikov (translation), on and on our SIGINT Chatter blogs about TRIGON and his CIA case officer Martha Peterson.

Documents of the Ministerium fur Staatssicherheit (Stasi) of the former German Democratic Republic (East Germany) show intercepted packets, destined for West German CIA agents, operating in East Germany. They contain one-time pads and instructions on how to receive and decipher messages on shortwave radio. These are published on the SAS und Chiffrierdienst website.

The Stasi's foreign intelligence service Hauptverwaltung Aufklärung (HVA) called their own numbers stations Einseitiger operativer Kurzwellenfunk or Welle 1 (lit. single-side operational shortwave radio or wave 1). They also used a speech and Morse generator to automate the transmission of their messages. You can watch an authentic speech generator running and see how it is operated or listen to the voice output (mp3). This is the machine behind the infamous East German lady. The machine was labeled in English due to the exported to many other Eastern Bloc countries. More at the Crypto Museum

Jack Barsky, born as Albrecht Dittrich in East Germany, was scouted by the Stasi, recruited by the KGB and sent to the United States under the false identity of Jack Barsky. His spying career lasted from 1978 until 1988. Every Thursday at 21:15 Hrs Barsky tuned his shortwave radio to a predetermined frequency and listened for a so-called radiogram from the KGB. These radiograms contained operational instructions that were encrypted into digits and sent in groups of five. A radiogram could take an hour to receive and write down and three hours to decrypt. Barsky’s KGB radiograms were transmitted from Cuba towards the United States. Watch Jack Barsky's interview where he talks about the radiograms.

In 1988 Vaclav Jelinek, a Czech StB spy who operated under the false identity of Erwin van Haarlem, was arrested by British Special Branch detectives while receiving a numbers message on a shortwave radio in his London apartment. One-time pads were found on microfilm, hidden in bars of soap. The pads enabled the detectives to decipher some of the received messages, which were later used in court. Jelinek was sentenced to ten years of imprisonment.

More recently, there were several spy cases in the United States, related to Cuban numbers stations. In the 1998, the so-called Cuban Five from the Wasp Network spy ring, agents of the Cuban DGI (Dirección General de Inteligencia), received instructions by encrypted messages that were sent each day by the Cuban HF numbers station "Atención". Another one was the Ana Belen Montes case, a senior US Defense Intelligence Agency analyst, spying for Cuba. She was arrested in 2001 and the federal prosecutors stated: "Montes communicated with the Cuban Intelligence Service through encrypted messages and received her instructions through encrypted shortwave transmissions from Cuba". More on the Belen Montes case in this FBI affidavit PDF Format.

In 2006, Florida International University professor Carlos Alvarez PDF Format and his wife Elsa Alvarez were charged with espionage and acting as agents for Cuba. The US District Court Florida stated: "Defendants would receive assignments via shortwave radio transmissions. These messages were encoded in five-digit groupings. Once received, Defendants would input these coded messages into their home computer, which was equipped with decryption technology contained on a diskette" More in the Alvarez sentencing.PDF Format

US State Department official Walter Kendall Myers PDF Format and his wife Gwendolyn Steingraber Myers were arrested in 2009 on charges of serving as illegal agents of the Cuban government for nearly 30 years. They acknowledged having received encrypted messages from the Cuban Intelligence via a shortwave radio they possessed. The Columbia State District Court indictment stated that "Cuban intelligence broadcasts encrypted shortwave radio messages in Morse Code or by a voice reading numbers" and also that "It was part of the conspiracy that Cuban Intelligence would and did broadcast shortwave messages in Morse code which were receive by Kendall Myers". More on this case in the Myers court indictment PDF Format and more about Cuban numbers stations in my article Cuban Agent Communications PDF Format.

Speech and Morse Generator © Detlev Vreisleben

Stasi Speech and Morse Generator "Stimme".
© Detlev Vreisleben.
Watch machine in action

Shortwave agent receiver  © Detlev Vreisleben

Specially designed interference-radiation free shortwave agent receiver type 32310.
© Detlev Vreisleben

SW-MW Convertor © Detlev Vreisleben

A 1950s SW to MW converter to receive messages from BND (West-German intelligence) on a normal MW radio. In those days, commercial SW radios were not available in East Germany. Unfortunately, the converter was notorious for its unwanted and strong interference radiation. © Detlev Vreisleben

A standard commercial shortwave receiver, ideal to covertly receive numbers messages. If discovered, this radio will not arouse any suspicion.

© Canadian Security Intelligence Service

A seemingly innocent AA type battery, cleverly crafted to contain clandestine items such as one-time pads or microfilm. This item was used by a foreign intelligence service.
© Canadian Security Intelligence Service

CIA one-time pad, used by Aleksandr Ogorodnik.
Source: KGB Archives

From Cold War to Cold Peace Top

Are numbers stations still useful in this age of global communications, Internet and satellite links? Yes! The so-called end of the Cold War did not bring a significant decrease in espionage activities. In the contrary, the Cold War is merely replaced by a Cold Peace where espionage is booming. In today's world, with the globalization of economics, politics and conflicts without borders, covert and illegal agents of Eastern, Western, Asian and Far East countries still operate extensively in each other's countries to gather intelligence and run operations. They still need a secure way to receive their operational instructions and messages. However, today, all modern communication systems are controlled by computers and are therefore by definition insecure.

Telephone, Internet and even satellite transmissions can be monitored. E-mails can be intercepted and read. Some government agencies have the money and resources to monitor communications and trace both sender and receiver. An example is the huge ECHELON project which globally intercepts and identifies all kinds of communications. In times of conflict, countries can simply block the Internet or other communications, or even simply switch off satellites. There have been successful tests to destroy satellites with missiles, making satellite communications unreliable during a serious conflict. Or did you really believe to continue using telephone or Internet between, let's say, Russia and the United States, if they were at war with each other?

Imagine a war broke out and intelligence personnel are operating behind enemy lines. The only secure and reliable way to communicate with them would be the good old-fashion long distance shortwave radio. But even in times of peace, some covert operations are so sensitive that discovering them would bring governments big problems or embarrassment. It is believed that some numbers stations continuously send fake messages, just to keep the lines open, ready for use. Those who monitor these stations are unable to notice when a station suddenly changes from sending random numbers to operational encrypted traffic. A good example is the Lincolnshire Poacher, sending messages of 200 groups, each and every day, for almost 40 years. Reasons enough why numbers stations are still active and useful. With their long and outstanding career of more than 70 years, the numbers stations have become an icon of espionage.

And still, every single day, numbers messages are transmitted all over the world, spoken in English, Russian, Spanish, Chinese and many other languages. Who's broadcasting and, even more intriguing, who's listening...?

Some recordings Top

Lincolnshire Poacher British foreign intelligence service MI6, a.k.a. SIS, with transmitter in Cyprus. and easily recognized by its introduction signal, the English folk tune The Lincolnshire Poacher.

Swedish Rhapsody Child This eerie mechanical child voice was a station of the Polish secret services SB and UOP.

Atención Station The well-known Cuban transmitter Atención, broadcasts for Cuban agents in the U.S. and South America.

Yankee Bravo German female voice, probably of KGB origin, introduced by the call sign Yankee Bravo.

Russian Male Station with unknown location, Soviet secret service KGB.

East German 'Stimme' Synthesized voice output from the East German 'Stimme' Generator .

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