The GP-7 was originally powered by a model 800-1 rotary inverter. Those are a bit hard to find, and they can easily be mistaken for mechanical sirens. There are lots of possible ways for a collector to power 800 Hz Navy radios:

• Use an original 800-1 inverter. Their cooling fans are very loud, though.

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KSM + MRCG Joint Crypto Operation

This year, we conducted a joint crypto operation with radio station KSM. KSM transmitted two different messages, one by CW and one by RTTY, both enciphered with an M-209 cipher machine. KSM is licensed under commercial rules, and thus is not limited by the no-ciphers restriction of ham radio stations.

Tim Sammons N6CC and Tom Horsfall WA6OPE copied the CW message despite less than favorable signal conditions. After they copied it, I successfully deciphered it with my M-209-B. Tim used his GRC-109, but I don’t know what rig Tom used. The original message is one that was received by Merrill’s Marauders in Burma around 1944.

I received an email from Steve Hobensack N8YE, who reported that he received the message at his home station and successfully deciphered it.

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http://www.nf6x.net/m209group

It can also be reached from the “Groups” menu under my web page banner.

Please check it out if you are interested in exchanging M-209 cipher messages with other crypto enthusiasts.

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I’ve never seen examples of real WW-2 era key lists, so I’ve come up with my own interpretation of what they might have looked like. I’ve also taken some creative license by adding an additional indicator to the normal M-209 message format, which I call the “Net Indicator”. Just for good measure, I also added a letter group count. The new format would look like this 33-group example with a net indicator of “SAMPLE”:

SAMPLE GR 33
KKETJ RNOYL YAOFG MRVMF VNAXD
UWDAR RIRBZ NARKN MOJFN NQSOY
IGIOC RWTNA RBSBU HVVKO NEHTG
RGLHL FIAXX YFOYU EKSAE FPAMG
QJSFJ OGRLP SWLPF IACGD WBWAJ
OYZAF JKTNZ SGSBL KQUCW QFCFQ
SKLCX KKETJ RNOYL

My idea of adding this net indicator was motivated by the desire to create more “lifelike” key lists for M-209 enthusiasts to use, without causing confusion when collectors inevitably publish their own key lists with conflicting key lists indicators.

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As a commercially-licensed station, KSM is not bound by the restrictions on use of cryptography that ham radio operators are. They’ll be transmitting two different messages, both enciphered with a WW-2 era M-209 Converter. MRCG participants will, in turn, attempt to receive those messages and decipher them.

From the MRHS announcement, here’s the broadcast schedule:

KSM will broadcast a prepared message consisting of 26 groups encrypted with the M-209 at 15wpm on all its CW frequencies beginning at 1100 Pacific time (1800Z) on Saturday 4 May.

These frequencies are (in kc):

426 (after an announcement on 500)
4350.5
6474.0
8438.3
12993.0
16914.0
22445.8

The message will be sent twice.

The usual KSM press transmission will begin at 1000 Pacific time (1700Z) at 25wpm and continue until the announcement for the crypto broadcast to give listeners a chance to tune to the strongest signal in their area.

Upon completion of the CW transmissions a longer message will be sent on all KSM RTTY frequencies, also encrypted with the M-209.

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Now, the big problem is that I’ve never seen actual M-209 key lists. I’ve come up with a plain text format for individual key tables, which I think I picked up from one of the M-209 technical manuals. I know that individual keys were identified by two-letter sequences called “key list indicators”. I know that keys were intended to be changed periodically, possibly daily (or possibly more or less often depending on activity level, but I’m sticking with daily for my purposes). I’ve seen a training film in which an M-209 key list is consulted, but the video transfer of the film is too blurry to make out useful details.

From these details, I’ve inferred what I think a key list might have looked like. I’m hoping to get some input from other crypto enthusiasts about the formatting, wording, etc.

I started working on this in preparation for a future announcement of an M-209 operator’s group similar to the Enigma World Code Group.

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This chapter covers recognition and deciphering of messages.

The M-209 is a cipher machine designed by Boris Hagelin, and used by U.S. forces during World War 2 for encryption of lower level traffic. It was known to be breakable by German forces, but it was still useful for low-level, high-volume traffic that only needed to be protected for a matter of hours. More details about the machine’s functioning and history can be found online at many places including Wikipedia and my own web page. M-209 machines are available on the surplus market, but they are somewhat rare and expensive (despite being among the least expensive cipher machines available). If you do not have access to a real one, you can use a simulator such as this excellent graphical simulator for Windows computers or the command-line simulator I wrote to help me understand the machine better.

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This chapter covers composition, encipherment and formatting of messages.

The M-209 is a cipher machine designed by Boris Hagelin, and used by U.S. forces during World War 2 for encryption of lower level traffic. It was known to be breakable by German forces, but it was still useful for low-level, high-volume traffic that only needed to be protected for a matter of hours. More details about the machine’s functioning and history can be found online at many places including Wikipedia and my own web page. M-209 machines are available on the surplus market, but they are somewhat rare and expensive (despite being among the least expensive cipher machines available). If you do not have access to a real one, you can use a simulator such as this excellent graphical simulator for Windows computers or the command-line simulator I wrote to help me understand the machine better.

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This chapter covers internal key settings of the M-209.

The M-209 is a cipher machine designed by Boris Hagelin, and used by U.S. forces during World War 2 for encryption of lower level traffic. It was known to be breakable by German forces, but it was still useful for low-level, high-volume traffic that only needed to be protected for a matter of hours. More details about the machine’s functioning and history can be found online at many places including Wikipedia and my own web page. M-209 machines are available on the surplus market, but they are somewhat rare and expensive (despite being among the least expensive cipher machines available). If you do not have access to a real one, you can use a simulator such as this excellent graphical simulator for Windows computers or the command-line simulator I wrote to help me understand the machine better.

…  Read More!

This chapter covers basic operation of the M-209.

The M-209 is a cipher machine designed by Boris Hagelin, and used by U.S. forces during World War 2 for encryption of lower level traffic. It was known to be breakable by German forces, but it was still useful for low-level, high-volume traffic that only needed to be protected for a matter of hours. More details about the machine’s functioning and history can be found online at many places including Wikipedia and my own web page. M-209 machines are available on the surplus market, but they are somewhat rare and expensive (despite being among the least expensive cipher machines available). If you do not have access to a real one, you can use a simulator such as this excellent graphical simulator for Windows computers or the command-line simulator I wrote to help me understand the machine better.

…  Read More!