Cryptanalysis of the Enigma immense problem and it gave a great deal of trouble. Work on a high speed machine had been started by Wynn-Williams of the TRE late in 1941 and some nine months later Harold Keen of BTM started work independently. Early in 1942, Bletchley Park were a long way from possessing a high speed machine of any sort. Eventually, after a long period of being unable to decipher U-boat messages, a source of cribs was found. This was the Kurzsignale (short signals), a code which the German navy used to minimize the duration of transmissions, thereby reducing the risk of being
Cryptanalysis of the Enigma defined somewhat differently in that era than in modern cryptography. First, there is the "identification" of the system in use, in this case Enigma; second, "breaking" the system by establishing exactly how encryption takes place, and third, "solving", which involves finding the way that the machine was set up for an individual message, "i.e." the "message key". Today, it is often assumed that an attacker knows how the encipherment process works (see Kerckhoffs's principle) and "breaking" is often used for "solving" a key. Enigma machines, however, had so many potential internal wiring states that reconstructing the machine, independent of particular