A Straight Dope Classic from Cecil's Storehouse of Human Knowledge

Who operates those weird "numbers stations" on shortwave radio?

August 18, 1989

Dear Cecil:

While scanning the shortwave radio bands recently, I discovered a station broadcasting five-digit numbers in Spanish. Each number was repeated twice before a new one was broadcast. It was a little strange, but I figured I had stumbled onto the Cuban Lotto numbers station.

Then last night I picked up a similar broadcast in English. It lasted about 25 minutes, then ended abruptly. A fellow shortwave enthusiast says these "numbers stations" are a big mystery and may somehow be tied into the CIA or drug smuggling!

The FCC and CIA were no help, so I turn to you.

Cecil replies:

It's spies, likely.

There are dozens of "numbers stations," some of which have been in business for decades. Yet no government or private agency has ever acknowledged them.

The stations broadcast in a variety of formats (three, four, and five digits, etc.) in languages ranging from English and Spanish to Czech, Korean, and Serbo-Croatian. The voice is often female and its unchanging inflection suggests that it may be machine-generated, like those wrong-number recordings used by the phone company.

At least some of the numbers stations are broadcasting coded messages. The messages have a definite beginning and end, start with an indication of how many number groups the message will contain, repeat each group carefully, and use standard-sized code groups (i.e., four or five digits), a universal feature of modern cryptography.

David Wise's book The Spy Who Got Away (1988), about a CIA defector, offers the following insight into how the codes (or at least some of them) work:

"A former CIA case officer with long experience in Moscow explained that … 'a transmitter is set up in Germany or even at [CIA] headquarters in Langley [Virginia]. The agent knows that at certain times on certain nights you will transmit to him, normally in five digit code groups. He is given a [one- time pad, or OTP], of which only one other copy exists, which the sender has.'

"The pages of a one-time pad consist of different, random five- digit groups of numbers that are used to encipher messages with the aid of a matrix, or number grid, that can be read much like the coordinates of a road map.

"Each page is destroyed after use. Since only one other copy of the pad exists, the code is unbreakable. The agent uses his copy of the one-time pad to decipher the message.

"The old Moscow hand explained what happens next. 'The OTP is on edible paper. Once he deciphers the message, he tears the pages out, burns them, flushes them down the toilet, or eats them — however he's been instructed. You can use [this] voice link to confirm or change a meeting.'

"He paused and smiled. 'Sometimes we would broadcast code groups just to make the Soviets think we had a lot of assets even if we didn't.'"

Interestingly, the volume of coded message traffic doesn't seem to have dropped appreciably with the end of the Cold War. I suppose that only makes sense. Even if you were running fewer spies than you used to, you'd keep the code numbers booming out at the same rate so as not to clue the bad guys should you have the need to expand your agent roster in the future.

It's reasonable to assume other folks besides the CIA are broadcasting code groups, too. But nobody will say publicly:

(1) exactly who's doing it;

(2) whether private parties are involved (some suspect drug traffickers because so many messages are in Spanish);

(3) where the stations are located (because of atmospheric reflection, direction-finding is difficult);

(4) how many of the messages are real and how many are dummies intended to lull eavesdroppers;

(5) who the intended recipients are (they can't ALL be Cuban agents in the U.S.); and, of course,

(6) what the messages say.

Clearly the time has come for a courageous subset of the Teeming Millions to get jobs with the world's national security agencies, find out the whole story, and then clue us in. (I'd do it, but I'm tied up this week.)

If they catch you, of course, you'll probably get the chair, but hey, can't make an omelet without breaking some eggs. For more details on number stations, see Big Secrets by William Poundstone (1983).

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