Grill (cryptology)

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The grill (Polish: ruszt), in cryptology, was a method used chiefly early on, before the advent of the cyclometer, by the mathematician-cryptologists of the Polish Cipher Bureau (Biuro Szyfrów) in decrypting German Enigma-machine ciphers.[1]


The grill method is described by Marian Rejewski as being "manual and tedious"[1] and, like the later cryptologic bomb, as being "based... on the fact that the plug connections [in the Enigma's commutator, or "plugboard"] did not change all the letters." Unlike the bomb, however, "the grill method required unchanged pairs of letters [rather than] only unchanged letters."[2]

The grill method found application as late as December 1938 in working out the wiring in two Enigma rotors newly introduced by the Germans. (This was made possible by the fact that a Sicherheitsdienst net, while it had introduced the new drums IV and V, continued using the old system for enciphering the individual message keys.)[3]


  1. ^ a b Rejewski 1984e, p. 290
  2. ^ Rejewski 1984c, p. 242
  3. ^ Rejewski 1984d, p. 268