The most interesting passage from Cryptonomicon that relates to a discussion earlier in the course is found on page 89. Here, Lawrence describes the most intriguing machine found at Station Hypo: at machine built by Commander Schoen and designed to break Japan’s INDIGO cipher. According to the book’s description, INDIGO was similar to ENIGMA, in that it was enciphered using a machine. However, unlike ENIGMA, none of the cryptanalysts had seen the INDIGO machine, so they had no idea how to tackle it. Amazingly, Schoen was able to reverse-engineer the cipher machine simply by analyzing the encoded messages and finding patterns in the numbers.
Of course, this section directly relates to our discussion of ENIGMA and its downfall. The main difference between the two, though, seems to be where the bulk of the security was. With ENIGMA, cryptanalysts struggled to break the code, even with the machine in front of them. According to the book, the major breakthrough with INDIGO was creating a copy of the machine.
After reading the passage, I was convinced that Stephenson had fabricated this part of the story. I found it highly unlikely that any person could reverse-engineer an elaborate mechanism by simply searching for patterns in encrypted knowledge. However, after a quick Wikipedia search, I found that this instance was actually based off of a real-life occurrence.
The actual cipher was named PURPLE (INDIGO was a great name for Stephenson to pick) and the main storyline remains the same: a machine was being used to encipher messages and no one knew what it looked like. The biggest difference between reality and the fictionalized story is that multiple people worked together to create the PURPLE machine, compared to the lone Commander Schoen in Cryptonomicon. Nevertheless, creating a complex machine by analyzing the numbers it output is still genius.
Image: "COBOL Rube Goldberg" by Phil Manker