Bletchley Park Codebreaker Honored

Rambo Tribble writes "England has awarded Raymond Roberts, one of the nine cryptanalysts responsible for breaking the Nazi Tunny code machine, (also known by the German designation Lorenz cipher machine) the MBE. Roberts is the last surviving member of the team which cracked the German army's cipher machine functionality, much like others at Bletchley broke the better-known Enigma machine."

Comments

Breaking Tunny

[mbone]

Tunny was broken because of a test message that had to be resent, and was re-encoded with the same key. The cryptographer was bored, and he made some abbreviations in the second encoding (which was manually typed). That put them out of phase, which meant that the message could be broken in crab-fashion. (Guess a word in the cipher text. If you are correct that gives you a little of the key and thus the decryption of the same block of characters in the other text. That, if you are lucky, will reveal another word, which gives more characters in the second text, which yields more in the first, making the entire decrypt fairly straightforward once you get going.) Breaking that message was enough to reveal how the machine worked, it was reverse engineered, and in operational use it was broken by computer basically from the start.

All of this because one operator got sloppy on one test message that wasn't even intrinsically important anyway. But, i think it is fair to say that more crypto is broken by sloppiness than by advanced math (not that the math might not be useful in exploiting the break).