Numbers Stations: A bad day to be a Cuban spy

SWLingPost-Spy-Numbers-Station

While band scanning last Sunday (September 8, 2014) I stumbled upon the Cuban numbers station HM01 on 11,530 kHz at 17:30 UTC.

It’s always intriguing to hear shortwave numbers stations, but I prefer those that stick to pure vocal number strings; HM01 has numbers with digital bursts between number sets, which is a more fatiguing listening experience.  Nonetheless, I kept it playing in the background as I tooled around the radio room Sunday afternoon, putting away supplies from my recent three week road trip.

WFL_015Several times during the HM01 broadcast, I heard the audio (not the AM carrier) drop in the middle of numbers sets and digital bursts. This isn’t the first time I’ve heard hiccups on HM01 (see this post from last year, for example), so I wasn’t terribly surprised. Then, close to the top of the hour, HM01 audio dropped for a minute or so, then switched back to five-number sets with no digital bursts between; though I wasn’t copying the message, I suspected that someone in the studio intentionally, perhaps in frustration–or else accidentally–started the broadcast from the beginning again.

At this point, I started recording. The five-number sets continue for about a minute, then the carrier unexpectedly drops:

Since it was near the top of the hour, and HM01 broadcasts only tend to last one hour, I didn’t expect to hear the broadcast repeat–and it didn’t, at least on 11,530.

Via a little band scanning, I discovered that HM01 had unexpectedly migrated 105 kHz higher, to 11,635 kHz. This broadcast audio also begins a little awkwardly. You’ll hear the audio drop; I scan for a few seconds,  then return to 11,635, and HM01 comes back. And this time, the numbers set sounds cleaner, with fewer problems. Here’s the recording:

I couldn’t help but chuckle over this…

Evidently, this message had some important content–otherwise they wouldn’t have re-broadcast the entire set the following hour, 105 kHz up from the original frequency (most likely protocol after technical difficulties). I imagine spies huddled around their radios, cursing at the interruptions and frustrated they had to listen for an additional hour; and I imagine the confusion at the broadcast site as they tried to diagnose the problem in a live broadcast. It’s during these little mistakes that numbers stations inadvertently tell us who they are (Radio Havana Cuba content has accidentally been played before on Cuban numbers stations).

Miami Herald: Cuban spies and shortwave numbers

towersI should note that we have several recordings and frequencies for the numbers station HM01, which is mentioned in this article. Very happy to see that they interviewed Chris Smolinski:

(Source: Miami Herald)

Even if you’re not a Cuban spy, you too can receive secret messages sent by Havana to its spooks in Miami, Washington and around the world.

Every week, one short wave radio station in Cuba broadcasts 97 messages coded in fax-like tones. A computer program easily available to the public changes the tones into numbers, and the Cuban spies then decode the numbers into words.

A second Cuban spy station transmits 16 messages per week in the dots and dashes of the 175-year-old Morse code – secret messages to Havana spies who may be older or less technologically savvy.

[…]The busiest Cuban station these days, and the only spy station in the world that uses the fax-like tones, has been baptized as HM01 by amateur eavesdroppers who run Web pages like Spooks List, Spynumbers, ShortwaveSchedule and Enigma2000.

It transmits 11 to 14 messages per day, a total of 96 per week, on the same schedule each week but using a dozen different short wave frequencies, said Chris Smolinski, 41, a Maryland software engineer who monitors the spy stations as a hobby.

Each message almost always has 150 five-digit groups, so that eavesdroppers cannot measure the true length of the text. And some of the 10-minute transmissions are phonies, designed to mask the real number of spies receiving them.

Anyone can hook up a radio receiver to a computer, where the DIGTRX program – widely used by ham radio aficionados to send and receive lengthy texts, turns the tones into numbers. Spies then use secret computer programs to turn numbers into text.

“HM01 is an ideal system because you don’t have to teach any to anybody. The computer does all the work,” said Smolinski.

For the less computer-savvy spooks there’s the M08a station, which broadcasts 16 messages in Morse code, developed for the telegraph in 1836, on a set weekly schedule and on many of the same frequencies as Hm01.

Read the full article on The Miami Herald website…

Cuban Numbers Station HM01: serving up a little confusion

WFL_015On occasion, I hear the Cuban numbers station HM01 on 5,855 kHz on weekday mornings.

It seems that many of the mornings as I listen, I hear HM01 making mistakes or at least experiencing “technical difficulties” (click here for a recent case in point).

Though I don’t often record HM01, I did record it on the morning of September 20, 2013––and, yet again, I heard what seemed to be HM01 tripping over its own tongue.

Instead of the broadcast starting with numbers to identify the transmission, then implementing intermittent RDFT data bursts as per usual, this broadcast begins in the middle of a data burst, then shuffles awkwardly into a “normal” broadcast.  I imagine an operative in the field scratching his or her head…

But hear this for yourself.  Either click here to download an MP3 of the recording, or simply listen via the embedded player below:

Rijmenants’ paper sheds light on Cuban numbers stations

WFL_015I’m always amazed by the remarkable talents and extraordinary knowledge of SWLing Post readers. Dirk Rijmenants recently commented on one of our Cuban spy numbers station postings:

[T]hanks for your work on this fascinating blog.

I have additional information on how and who used these Cuban numbers stations. I composed a paper based on FBI and court documents. “Cuban Agent Communications” can by found in the Papers section of my website.

Here’s the direct link (pdf):
http://users.telenet.be/d.rijmenants/papers/cuban_agent_communications.pdf

Have fun reading!

Dirk Rijmenants
Cipher Machines & Cryptology

I’ve read Dirk’s paper, which does, indeed, shed light on the process of receiving and decoding numbers. Most of all, it exposes the vulnerability and fallacy of using anything other than one-time decryption keys and single-use pads. Why? Most of what the FBI has learned about Cuban numbers came from laptops that were used to help decrypt coded messages–an unnecessary procedure when numbers can simply be decoded on note pads that can then be burnt or destroyed.

But don’t take my word for it–download and read Dirk’s paper Cuban Agent Communications” by clicking here. Also, be sure to check out Dirk’s blog and cryptology website; I’ve bookmarked both.

Thanks for sharing your findings, Dirk!

Even numbers stations make mistakes

WFL_015On February 5th, 2013, the Cuban numbers station widely known as HM01 struggled to maintain its composure following an awkward studio error.

In this particular case, I started recording a few seconds prior to the carrier, at which point you’ll hear a couple of minutes of “dead air” (silence). The broadcast starts around 2:25, cutting into the middle of a data burst; the station then goes silent before it comes back on at 5:15 with numbers, then abruptly stops. At 6:15 the station restarts the numbers broadcast in earnest.

Download the MP3 of the full recording by clicking here, or listen via the embedded player below:

Click here to view the Archive.org with original audio files.

Shortwave Radio Recordings: Listen to Cuban Spy Numbers Station HM01

WFL_015Numbers stations have always been a dark oddity that pop up from time-to-time in the course of shortwave radio listening. There is unquestionably an air of mystery and intrigue which surrounds them. With the release of the movie The Numbers Station, many non-SWLers may be enticed to explore the HF bands.  A good thing, as it may draw fresh interest to this classic radio hobby.

I have heard numbers stations since I first started listening to shortwave radio broadcasts some thirty years ago, and I find that I often pause to listen (and to wonder) when I come across one on the bands.  The numbers station I hear most often, though the country of origin cannot be confirmed, is in Cuba–well, at least, we’re pretty certain of that. The same female voice, reading numbers in Spanish, has been Cuba’s calling card in the spy numbers world for some time.

Two weeks ago, on a Sunday morning between 10:00-11:00 UTC, I captured the Cuban spy numbers station widely recognized as HM01 (Hybrid Mode Number 01) on 5,855 kHz. HM01 broadcasts a mixture of AM voice and digital file transfer modes intermixed within the same transmission. The voice heard is the familiar Spanish female voice described above; the digital portion of the broadcast uses a mode called RDFT, a differential phase shift keying mode that has never become popular or standard in the ham radio world. If you’re feeling adventurous, the Windows software DIGTRX (download here) can decode RDFT.  Let us know what, if anything, you discover…

You can click here to download the entire HM01 broadcast as an MP3, or simply listen via the embedded player below: