The final Enigma code is taxing the network of computers

Thousands of users around the world have joined the M4 Project, using spare computing power to crack the codes.

The messages were encoded using the German Enigma machine, and outfoxed wartime experts at Bletchley Park.

Project leaders have already failed to crack the last remaining message, but insist it can be broken.

The three messages were unearthed by amateur historian Ralph Erskine, who submitted them to a cryptology journal in 1995 as a challenge for codebreakers.

Last crack

They were sent in 1942, during a period when the Allies were unable to crack German codes because of the introduction of a new code book and a more complex version of the Enigma machine.

SOLVED CIPHER #2 Found nothing on convoy's course 55°, [I am] moving to the ordered [naval] square. Position naval square AJ 3995. [wind] south-east [force] 4, sea [state] 3, 10/10 cloudy, [barometer] [10]28 mb [and] rising, fog, visibility 1 nautical mile

Nazi codes cracked online

Stephan Krah, a German enthusiast, wrote the M4 Project software - named after the M4 Enigma machine used to encode the messages - in an effort to unravel the codes' mystery.

The first code was cracked on 20 February, and was confirmed as a message from the commander of a German U-boat, Kapitanleutenant Hartwig Looks.

The second resolved code was less dramatic than the first, which detailed the aftermath of a clash with an Allied vessel.

The newly-deciphered code is little more than a status report and a confirmation of position.

THE UNSOLVED CIPHER HCEY ZTCS OPUP PZDI UQRD LWXX FACT TJMB HDVC JJMM ZRPY IKHZ AWGL YXWT MJPQ UEFS ZBCT VRLA LZXW VXTS LFFF AUDQ FBWR RYAP SBOW JMKL DUYU PFUQ DOWV HAHC DWAU ARSW TXCF VOYF PUFH VZFD GGPO OVGR MBPX XZCA NKMO NFHX PCKH JZBU MXJW XKAU OD?Z UCVC XPFT

Confirming the break on the M4 Project website, Stefan Krah said efforts would now shift back to the last message, actually the first of the three original submissions.

Previous efforts to crack the code exhausted the combinations available on German army and three-ring Enigma machines, but did not try all combinations relevant to the complex four-ring Enigma used to encode the messages.