## Cryptography

#### The History and Mathematics of Codes and Code Breaking

Here’s Aubrey’s paper on the wheel cipher [PDF].

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1. #### Preston Boyden

This paper is informative and concise. Aubrey does a good job of explaining the necessary background, which isn’t much, and then diving right into a description of what the wheel cipher is and how it works. Although the paper wouldn’t have suffered from a little more detail, it certainly works.
The explanation of the cipher’s use is practical, giving an example walkthrough of how one would encipher and decipher a message. I particularly liked the math demonstrating how many disk combinations there were and how long it would take the Germans to “brute force” the cipher.
Several weaknesses of the cipher are discussed and countered, but I couldn’t help but wonder why frequency analysis wasn’t one of them. It seems that the disks simply create a substitution cipher, that could be solved by FA, but maybe I’m missing something.
Other than that, I enjoyed reading this paper, especially since we haven’t covered it at all in the course, it was all interesting and new material. Good job!

2. #### Preston Boyden

Nevermind that penultimate paragraph in my comment, I wasn’t thinking clearly. Of course you couldn’t use frequency analysis. My bad.

3. #### Tyler Merrill

This exploration of the Wheel Cipher achieves clarity of history through the explanation of both instances of invention. By presenting the use of Jefferson and Bazeries ciphers, the complete history is understood. The history section is complete and thorough.

From this explanation, the cipher seems simple. This may be because the explanation was clear or because the cipher was indeed simple. Either way, this section conveys concisely how to encipher a message using the Wheel cipher. It also shows how decryption is impossible. The inclusion of the inconvenient nature of using a Wheel cipher helps to explain the lack of use during Jefferson’s time. However, there is not much about the impact of the cipher in World War One. This may however, be a result of the cipher having little effect on the war.

The demonstration of the inability to use brute force to solve a problem added to the discussion of the impenetrability of the cipher. The explanation of the kappa method is vague. It only describes the method very generally, which can create confusion. A deeper discussion of one potential decryption method could be better than an overview of a few. I also did not find any connection to other ciphers.

The discussion of the history and the method of encryption dominate this paper, while decryption falls behind. This is understandable because the cipher was unbreakable unless there was some pattern used in the discs. Because the history is more useful, it is important to focus on this. This was a good paper that focused on the interesting points of the Wheel cipher.