Challenge M-209

M-209 homepage
Cipher Machine Challenges


This challenge tries to measure your ability to solve ciphered messages created by the cipher machine M-209.
There are twelve problems. You can solve any of them. However, if you want to win the Challenge, you must solve all of them. I hope you will have as much pleasure solving these as I had when I solved the problems of Dirk's Challenge.

You can use my C446 simulator or any other correct Hagelin program, to decipher the messages. You can also use, a genuine M-209 cipher machine.

How to participate

It is very simple. You send me your solution for each problem by email . Please, put the following text in the subject line: "M-209 CHALLENGE: Solution to the Problem" .

But before sending any solution, you need to register. To do that, send me an email with the solution to the Registration Problem. It is easy, because the key is known. In the subject line, put:
"M-209 CHALLENGE: Registration : <your name (or nickname)> : <your country>".

Good Luck!

Why did I create this challenge?

Firstly, to provide fun cryptologic puzzles to solve.

Secondly, to prove that the M-209 is an encryption machine that offers serious security if properly used. In the Cryptologic literature, it is often seen as a cryptographic means offering very little security. A specialist in history of cryptology will not have failed to notice that the last issue of my challenge (the 12th) is modeled on the challenge that was proposed to W.F. Friedman to test the security of the Hebern's machine: 10 messages, in all about 4,000 letters and several probable words were given. If Mr. Friedman would have tried to solve my challenge, it would have failed and the US military would have used as a means of encrypting high-level the M-209. On the other hand, American cryptanalysts would notice the shortcomings of the regular stepping of the wheels and they would have proposed improvements. Thus Sigaba machine would have looked like a CX-52 (or German C-41). Of course, all of this is science fiction.

Errata and remarks

The plain text of the problems gives you some facts about the history of WWII and the Korean War. Sometimes these texts (or the introductory texts) aren't absolutely correct or the way in which the M-209 device is used is not correct either. The Errata page will contain any interesting remarks you send me.

When sending me your remarks, in the subject line only put: "M-209 CHALLENGE".

Other cryptographic challenges or cryptographic puzzles

Dirk Rijmenants
Torbjörn "Toby" Andersson
Didier Muller
Challenges (in French) centered around secret agent Tamara.
Tony Sale
Anoraks Corner, Can you break Enigma? Scenari
Breaking genuine War messages