Reminds me of how Bletchley Park broke some of the Enigma ciphers. The operators were supposed to abide by certain rules when making the 3-letter "keys" -- but

Reminds me of how Bletchley Park broke some of the Enigma ciphers. The operators were supposed to abide by certain rules when making the 3-letter "keys" -- but they inevitably picked letters next to each other on the keyboard, used the same letters repeatedly ("AAA"), used the same key "pairs", used words, names, etc.