The History and Mathematics of Codes and Code Breaking

Expository Essay - The M-209 Cipher Machine

Here's Rob's paper on the M-209 cipher machine [PDF].


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  1. Rachel Lundberg

    The major strength of this paper is its clarity. Your descriptions are succint and easy to understand. The M-209 was clearly a complex machine, but your method of explaining it was simple and effective. The example encryption and the table were particularly helpful.

    You did a great job of explaining the advantages of the M-209 (its light weight, its ease of use, etc.) and how these advantages made it so effective. This was further strengthened by your comparisons to other cipher machines such as Enigma and SIGABA. I especially like the point you made about the M-209 being more effective in situations where communications only needed temporary security.

    I would have liked to see more of the cryptanalysis angle in this paper. You mention that the machine "yielded patterns that could be analyzed" but do not really go in depth. You also bring up that the patterns appeared especially in messages of more than 150 characters, but I'm left wondering why that is.

    This is a strong paper overall. The process was easy to follow, the connections give weight to your points, and it wraps up nicely. I hadn't heard of the M-209 cipher machine before, and I feel that your paper has done a good job of informing me.

  2. Preston Boyden

    Overall, this is a very good paper. I thoroughly enjoyed reading it and learning about the M-209. The history of its creation and use is full yet concise, and connections to material we have studied in class are abundant.
    The explanation of how the M-209 works is clear, and the table that shows the translation of HAGELIN to ERQNYJY is very helpful.
    I like all of the connections Rob makes to other topics/ciphers from the course. He compares its speed to the Navajo Code, relates its size and weight to the Enigma machine, and explains the advantages it has over differing systems.
    He also talks about the weaknesses of M-209, and explains why it was still such a popular mechanism in the military.

    Though Rob was clearly able to relate much of this material to topics we have discussed, nearly all of his paper is clearly based on independent research. I didn't know anything about the M-209 before reading this paper, and yet I feel that I understand very clearly how it works. This makes a great supplement to our readings in Singh. Nice job, Rob!

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