The Enigma machine was the notorious German decoding apparatus, whose seizure and use by the Allied forces has enabled a detailed knowledge on many strategic and tactic German plans.
The philosophy and working principles of the machine were the base for all modern encryption systems.
The machine that was exhibited in the Bletchley Park Museum since the end of WWII was reported stolen on April 1st 2000. It was mailed back to a BBC reporter on October 2000 and it is reported that the 3 cylinders of the machine were missing. The existence of a ransom note of £2,.000 for the return of the cylinders was not confirmed.
It is believed that the thieves after not being able to sell the machine to a collector, chose this method to "compensate" themselves. The machine is one of three, known to be in existence till today.