February - August 1942.
On February 1st SHARK went onto an entirely separate key using 4 wheels
instead of 3 and a new reflector.
pictiure of 4 wheel Enigma.
The 4 Wheel Enigma.
1. Two fourth wheels, Beta and Gamma.
2. Two "thin" reflectors, Bruno and Ceasar.
3. Any combination could be used.
4. A combination stayed in force for one month.
5. Beta and Gamma ring setting always at Z.
6. The fourth wheel could be set to any of 26 positions but did not turn
during message entry.
7. With the fourth wheel set to A, with Beta/Bruno or Gamma/Ceasar,
the machine was equivalent to a three wheel Enigma.
8. The number of start positions now:. (26)^4 = 456,976.
The wiring of wheel and reflector had been given away by German security
"Time 14.47 date 17/12/41 From W/T Station Adm. Comm. U-Boats. E bar 551,
Service No 166 wrongly enciphered. Contents: U.131 reports: Am able to dive.
Have been hunted by 4 destroyers". "Time 16.30 date 17/12/41. From Mueller. E
bar 551 decyphers with setting B.".
A reencipherement from DOLPHIN of Admiral Doenitz's message to the Fleet on
suceeding Admiral Raeder.
This page was originally created by the late Tony Sale the
original curator of the Bletchley Park Museum