An amateur cryptologist's Internet project is using idling computers to help crack three Nazi codes that eluded the Enigma codebreakers of the Second World War.

Launched in January, the project has already broken one of the three messages, from a U-Boat commander forced to dive during an attack on November 25, 1942.

The computers of 2,500 strangers are now whirring away, trying to decode the remaining two. You can volunteer your computer here.

Stefan Krah, a German-born cryptologist from Utrecht, in the Netherlands, started the network in January after writing a program that combined the brute force of connected computers with a mathematical formula based on previous codebreaking work.

He offered the software to readers of two online bulletin boards with the words: "Clearly the project is from the 'Because we can' department. Is it realistic to hope that anywhere between 10-100 people would take part?"

On Thursday, Krah said he was amazed by "the exponential growth of participants."

"I was the only participant when it all started on January 9. About five people joined and participated regularly after I announced it on the lfs-chat mailing list," he wrote in an e-mail.

Together the computers are now marching through the 150 quintillion permutations of each letter that made the Enigma, which was used to direct devastating U-boat attacks against Allied shipping in the Atlantic, the most feared encoding machine of the war.

So confident were Nazi commanders in the Enigma that even when its messages were clearly being decoded by mathematicians at Bletchley Park, Britain's secret codebreaking base in Buckinghamshire, England, they refused to believe that the machine itself had been compromised, instead thinking spies were tipping off the Allies about the location of U-boats in the Atlantic.

The first success of Krah's "M4" project, named in honor of the final, upgraded Enigma that managed to perplex Alan Turing, the brilliant British logician credited with the breaking of the code, came on February 20.

From the scramble of 196 letters, passed 63 years ago through the Enigma's four decoding rotors, came the message:

"Forced to submerge during attack, depth charges. Last enemy location 08:30h, Marqu AJ 9863, 220 degrees, 8 nautical miles, (I am) following (the enemy). (Barometer) falls (by) 14 Millibar, NNO 4, visibility 10."

The location of the sender and a check of existing records showed that the message was sent by Kapitaenleutnant Hartwig Looks of U264, a German submarine that was eventually sunk in the North Atlantic in February 1944 by depth charges from the British sloops HMS Woodpecker and HMS Starling.

Krah said Thursday that the first message was deciphered by just 45 machines. The failure, so far, of the combined power of thousands of hard drives has raised the question of whether the last two will ever be cracked.

"Of course there is no guarantee that another break will occur at all — there is simply a fair chance," he said.

The two messages facing Krah and his allies were first published in Cryptologia, an academic journal, in 1995 by Ralph Erskine, a naval historian from Belfast, Northern Ireland.

The codes were among the thousands that sat, unbreakable, for ten months during 1942 as the Allies struggled to catch up with the M4 upgrade of the Enigma.

Unbreakable? The remaining messages:

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 TKCF VOYF PUFH VZFD GGPO OVGR MBPX XZCA NKMO NFHX PCKH JZBU MXJW XKAU OD?Z UCVC XPFT

TMKF NWZX FFII YXUT IHWM DHXI FZEQ VKDV MQSW BQND YOZF TIWM JHXH YRPA CZUG RREM VPAN WXGT KTHN RLVH KZPG MNMV SECV CKHO INPL HHPV PXKM BHOK CCPD PEVX VVHO ZZQB IYIE OUSE ZNHJ KWHY DAGT XDJD JKJP KCSD SUZT QCXJ DVLP AMGQ KKSH PHVK SVPC BUWZ FIZP FUUP