Today I Learned, Part 2

Some of this I didn’t technically learn today, but here goes:

  • Bazeries was a bit stubborn, to put it politely. His last book was filled with contempt and vitriol, although on the plus side, Kahn said that made it among the most interesting reads in an otherwise dry field. Even so, he denied a perfectly valid breaking of his wheel cipher.
  • Speaking of wheel ciphers, I had no idea that Jefferson’s system was in use by the Army into the 20th century!
  • French cryptanalysis was leaps and bounds ahead of any other European country at that time, perhaps with the exception of Austria-Hungary.
  • The English, on the other hand, relied on pure dumb luck to decipher enemy messages during WWI. They happened to capture German code books — no cryptanalysis required.
  • The English were not exactly helpful towards the French, either. Insisting that the French share their cryptanalytic findings, the French replied with something to the effect of “one of our ships was torpedoed by the Germans not long ago — why didn’t you warn us?” The English replied with something like “well, it would be dangerous to our intelligence efforts if that information fell into the wrong hands”, to which the French said “would you feel the same if it were an English ship?” That pretty much killed the conversation about cooperation on intelligence operations.
  • England wasn’t totally incompetent, though: by the end of the war, they used what David Kahn called the best cipher of that era, “Cypher SA”.
  • This cipher included polyphones, or code groups that have multiple meanings. The method for deciphering the messages essentially uses the character from the last code group as part of the “key” to decipher the current code group, giving you the proper meaning while confounding cryptanalysis. It’s remarkably similar to cipher block chaining (CBC) mode in modern block ciphers, where the previous block “feeds” into the next, and if one gets scrambled, the remainder of the message is scrambled as well.
  • England wasn’t alone in their cryptographic floundering — Germany flat-out refused to use ciphers that weren’t Teutonic in origin, and their cryptanalysis division was nonexistent for most of the war.
  • England’s first offensive move of the war? Cutting Germany’s transatlantic cables!

I’ve been sick the past week, and haven’t devoted any time to the Cryptopals challenges, but I have a goal of at least looking at the current problem at least once a day. This, combined with reading Codebreakers, will make up my daily routine (after work, that is). As for blogging, I’ll write at least one post per week. Any less and I’ll lose steam — any more and the quality is likely to suffer, unless I have something I absolutely have to write about. With that, I’m signing off. More to come!

1 Comment Today I Learned, Part 2

  1. Pingback: Today I Learned #4 | Crypto Padawan

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