The grill (Polish: ruszt), in cryptology, was a method used, chiefly early on, by the mathematician-cryptologists of the Polish Cipher Bureau in decrypting German Enigma machine ciphers. Cryptography (from Greek kryptós, hidden, and gráphein, to write) is, traditionally, the study of means of converting information from its normal, comprehensible form into an incomprehensible format, rendering it unreadable without secret knowledge — the art of encryption. ... The Biuro Szyfrów ( (?), Polish for Cipher Bureau) was the Polish agency concerned with cryptology between World Wars I and II. The Bureau enjoyed notable successes against Soviet cryptography during the Polish-Soviet War, helping to preserve Polands independence. ... This article is about algorithms for encryption and decryption. ... In the history of cryptography, the Enigma was a portable cipher machine used to encrypt and decrypt secret messages. ... This article is about algorithms for encryption and decryption. ...

The grill method was described by Marian Rejewski as being "manual and tedious" 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." Marian Rejewski (probably 1932, the year he broke Enigma). ... The bomba (plural bomby) was a special-purpose codebreaking machine designed by Polish cryptanalysts and used to crack the German Enigma machine prior to World War II. A bomba was designed to exploit an obscure but fatal weakness in the Enigma cipher. ...

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.) Look up December in Wiktionary, the free dictionary December is the twelfth and last month of the year in the Gregorian Calendar and one of seven Gregorian months with the length of 31 days. ... 1938 (MCMXXXVIII) was a common year starting on Saturday (link will take you to calendar). ... SD Insignia Patch The Sicherheitsdienst (SD, Security Service) was the intelligence service of the SS. The organization was the first Nazi Party intelligence organization to be established and was considered a sister organization with the Gestapo. ...

References

• Władysław Kozaczuk, Enigma: How the German Machine Cipher Was Broken, and How It Was Read by the Allies in World War Two, edited and translated by Christopher Kasparek, Frederick, MD, University Publications of America, 1984, pp. 242, 268, 290.