May 01, 2005 in Tech
Numbers stations are a phenomena unique to shortwave radio. These stations are generally found outside the normal AM and shortwave bands, although they occasionally interfere with commonly used shortwave frequencies. They generally consist of an automated female (or male) voice reading sets of numbers or phonetic letters, punctuated by morse code, audio tones, and even bits of music.
Shortwave radio hobbyists have long speculated that numbers stations are used by spy agencies to communicate with agents out in the field. The numbers, generally in groups of four or five, use a strong form of cryptography called a one-time pad. The person receiving the message transcribes the message by hand using the one-time pad, a dissolveable sheet of paper listing the numbers required to decrypt the transmission. Afterwards the pad is destroyed. This method of transmission offers total anonymity, and as long as the pad is not reused or intercepted, it is totally secure.
A number of musical groups have used recordings of numbers stations in their music, most famously Wilco on the album Yankee Hotel Foxtrot. Numerous media outlets in recent months have run pieces on numbers stations, including the Washington Post, NPR and the BBC.