## Cryptography

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

On Elonka’s website, there is an explanation and solution to the Smithy Code. The Smithy Code was embedded in the ruling for a plagiarism trial concerning Dan Brown’s The Da Vinci Code. Justice Peter Smith italicized several letters which spelled out “S m i t h y c o d e J a e i e x t o s t g p s a c g r e a m q w f k a d p m q z v -” — “Smithy code” is in English, and the rest is ciphertext which evidently involves a polyalphabetic substitution cipher. According to the explanation, Smith used a series of Caesar shifts based on the letters that correspond to the numbers of the Fibonacci sequence. Usually, this would be 1-1-2-3-…, which would correspond to A-A-B-C-…. However, Smith added a twist and replaced the letter B with the letter Y. He then used a grid of the Caesar shifts and found the plaintext letter in the grid, then traced it up to the letter at the top of the column to encipher it, similar to the way one would decode a Vigenère cipher.

In class, we have discussed Caesar ciphers, polyalphabetic substitution ciphers, and the Vigenère cipher (a type of polyalphabetic cipher). The Smithy Code was an intricate interweaving of all of these methods and a method inspired by The Da Vinci Code (the Fibonacci Sequence), because of the novel’s relevance to the trial. It was a fascinating look into a method by which several ciphers can be used, and how far common knowledge and research about cryptography has come in order for these methods to be implemented.

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## 1 Comment

1. #### Derek

I appreciate that Judge Smith approached his work with this much enthusiasm! The encryption method is a Vigenere variant–another polyalphabetic substitution cipher (which is fun to say). I wonder how long it would have taken someone (the Kryptos group, maybe) to crack it without the judge’s hints. There’s precious little ciphertext to work with!