cilly

Any predictable facet of the Enigma Machine cipher due to operator error or laziness, whose existence helped the Allies to break the code.

Noun

  1. Any predictable facet of the Enigma Machine cipher due to operator error or laziness, whose existence helped the Allies to break the code.
    • Another type of cilly was the repeated use of the same message key, perhaps the initials of the operator's girlfriend […] - 2000, Simon Singh, The Code Book:
    • Answer c is a reference to a cilly, which was a three-character message key used in the German Enigma machine. - 2002, Ronald L Krutz, Russell Dean Vines, The CISSP Prep Guide: Gold Edition:
    • Taunt describes the work involved in breaking Enigma messages, cribs, cillies, the Herivel tip, help from Bombes and more. - 2005, Brian J Winkel, Cipher A Deavours, David Kahn, Louis Kruh, The German Enigma cipher...

Origin

Uncertain; possibly a pun on silly and the letters CIL used as a cryptographic key.

Forms

cillies