An anonymous reader writes: A rare 1944 four-rotor M4 Enigma cipher machine, considered one of the hardest challenges for the Allies to decrypt, has sold at a Christie’s auction for $437,955. As noted by Christie’s, the M4 Enigma has a special place in computing history as the Allied efforts to break its encryption led to the development of the first programmable computer, the one developed at Bletchley Park that was used to secretly break the M4, giving Allied forces visibility into German naval planning during the Battle of the Atlantic until its surrender in mid-1945.

The M4 Enigmas are considered rare because they were made in smaller numbers than three-rotor machines. After Germany capitulated, the country ordered troops to destroy remaining Enigmas in order to keep them from Allied forces. After the war Winston Churchill also ordered all remaining Enigmas destroyed to help preserve the secret of Allied decoding successes at Bletchley. The M4 Enigmas were made on the order of Admiral Karl Donitz, the commander of the German U-boat fleet, who had concerns over repeated Allied successes against his submarines. The M4 became available to the U-boat fleet in May 1941, preventing Allies from knowing where German’s U-boats were positioned for almost a year until Turing and Joe Desch in Dayton, Ohio developed the computer that broke M4 encryption to decipher German messages. By mid-1943 the majority of M4 Enigma messages were being read by the Allies, but it was not until the 1970s that knowledge of the Allied successes against the Enigma was made public. “Rival auction house Sotheby’s sold an M4 Enigma last year for $800,000, which may have reached a higher selling price because it was one of one of 15 Enigma machines found in a bunker at Germany’s key Northern European naval base in Trondheim, Norway, which Germany had occupied since 1940,” adds ZDNet.

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Source: Slashdot – Rare and Hardest To Crack Enigma Code Machine Sells For 7,000