This will be long, but hope it provides more insight about the notorious numbers stations. I won't get into some of why or how I know about the (in)famous "numbers" stations. Suffice it that I routinely listened to them during the Cold War on the MF and HF bands (i.e. 300 kHz - 30 MHz). Frequency selection was based upon MF and HF radio wave propagation for smoothed sunspot number, geographic location of transmitter and the intended recipient(s), and time of day at the Great Circle midpoint between transmitter and receiver. Frequencies that would work from East to West Germany would not work from Moscow to North America,, and frequencies that would work during mid-day would not work at night. One could direction find the transmitter easily. Knowing the other data above you could get an idea of possible general geographic regions for the intended recipient, but it was far from definitive. It would have to be combined with a host of other information about the probable recipient to begin to narrow it down. At best it could be used alone to make a suspect location less likely. The intended recipient would have to know the times and frequencies on which to listen for their numbers station. Your general description of them is excellent. Some additional notes about them. Every one I encountered or was aware of, including historic, defunct stations, used a One Time Pad. Plaintext was converted to numeric plaintext using a straddling checkerboard. These varied by language being encrypted. For a specific language, there were variants. Code books were frequently used to reduce common words within the kinds of communications taking place to two, three and sometimes four digit numbers. The combination of straddling checkerboard and code book could make the ciphertext quite compact, reducing transmission time. For the morse code stations, they usually used reduced versions of the numbers. In International Morse Code, the numbers are all five dot/dash characters. Unambiguous letters similar to them with only two or three dot/dash combination were used instead. As an example, the numeral "1" is normally "* - - - -" and the cut down version used would be the letter "A", "* -", and so on with "2" = "U", "6" = "N", etc. There are examples of these online (Google for them) with some variants. The first code group transmitted usually (but not always) identifies the one time pad page being used. The pad page ID is no different from the rest of the ciphertext; it's just another code group. One of the most notorious uses of a numbers stations was the communication between Cuba and a mole within the CIA, Ana Montes. She was arrested in 2001, plead guilty in 2002 to avoid a death penalty trial, and was sentenced to 25 years. She's due to be released some time in 2023. The evidence photo of her straddling checkerboard is in the Wikipedia article about her, which they call an "encryption/decryption cheat sheet". In addition, a documentary about her also showed the shortwave receiver she used and the information they found about the Cuban numbers station schedule and frequencies for their transmissions to her. The imperative of using a one time pad once, and only once is demonstrated with the VENONA project, which ultimately decrypted a little over 2000 Soviet messages spanning 1942-1945. It resulted from the Soviets inadvertently printing duplicates of 35,000 one time pad pages during the war. Their urgent need resulted in a decision to use them, and distribute them to widely separated units/organizations in different, unrelated commands. A clear testament to the tenacity of the OSS and later CIA at the time, a few of their brightest suspected pad page reuse and an extremely arduous undertaking ensued to find the duplicate usages . . . which made decrypting both messages using the same pad page relatively trivial, in spite of a straddling checkerboard and using code book numerals. The VENONA Project unmasked Julian and Ethel Rosenberg with their co-conspirators in the early 1950's. Effort to find dupe page usage during WWII and decrypt the communication continued into the 1980's. Had the Soviets destroyed the dupe pages and replaced them, none of those intercepted one time pad messages would have been decrypted. Those that claim it can be broken don't understand one time pad and its underlying math. The two most important rules are truly random number or letter generation for the pad, and never, ever, using the same pad key twice.

Much appreciated sir. I'm a year 2 student of Criminology and Security Studies and I came across "Number Stations" while reading about 'means of intelligence collection'. I decided to learn more about it and fortunately, I found this well-explained video of yours about it. I hope you can also make another video on "One-way Voice Link (OWVL)" Thank you once again! Much love from Nigeria 🇳🇬 ❤️

This is amazing Nils! It is getting very hard to think of a cipher topic that CrypToll2 doesn't cover.

Your digit voice data, may be an interesting sample set to expand your steganography vid(s) demonstrating beyond the 👂 while below the static noise for the possible existence of subliminal 'burst' message transmissions.

I was waiting on this

As of March of 2021: G06 fully Retired from Service. There is no more German Stations Active.

I have a feature request: keyboard shortcuts for those big starting and stopping execution buttons. What fascinates me is how the secret agent recipients of these number station messages might have received the key to the encryption. There's so much risk involved with key distribution.

Great stuff! Just one comment: the visualization of the Morse Code running from right to left is quite counter-intuitive given that oscilloscopes, etc, scan from left to right, and most of us also write from left to right.

Thank you! I created a "cipher" for my animation, Blue Angel Series, but letters from the Phonetic Alphabet are used. The main character, Angel, tunes in a "letters station" in order to get a code. I would like to develop an algorithm for this cipher.

Hat die Minustaste bei der Eingabe der URL geklemmt? ;-) www.numbers-stations.com/e03/