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When the Berlin Wall began to crumble in 1989, East Germany's Ministry for State Security, the Stasi, decided to destroy all the evidence of 40 years of spying on fellow countrymen. But, like something out of a Cold War comedy, the Stasi's cheap shredders broke soon after they started, leaving agents to use their hands to tear the records into 600 million pieces, some as small as a fingernail. The pieces were supposed to be destroyed, but the Stasi never got around to incinerating them. To this day, they fill around 16,000 garbage bags stored in the basement of the former state security headquarters in Berlin, their secrets lost in a pile of millions of tiny shreds of paper.

But that was before the e-Puzzler. Using a machine that runs software that they developed, scientists in Berlin plan to use the world's most sophisticated pattern-recognition technology to put the shredded Stasi files back together, and help piece together a part of the past that was long considered lost forever.

The e-Puzzler is really the next step in a process that started back in 1991, when a team of 45 civil servants set out to manually reassemble the documents. Working with Scotch tape, they pieced together 90,000 pages, revealing Stasi collaborators and their victims. But by August 2009, the team was down to eight people, and they had only gone through 350 bags. At that pace, sifting through the rest would take another 800 years.

So, with the idea of getting a machine to finish what humans had started, scientists at the Berlin Fraunhofer Institute of Production Facilities and Construction Technology developed the e-Puzzler, whose software can digitally put back together even the most finely shredded papers. Here's how it works: A computerized conveyor belt feeds up to 10,000 shreds of paper through a digital scanner. The e-Puzzler software then clusters the shreds according to search attributes like color, texture, typeface and outline — much like a person might start to piece together a puzzle. After processing the information, the machine displays a digital image of the reconstructed document on a screen.

"We demonstrated back in 2007 that we can match smaller amounts of document shreds," says Bertram Nickolay, the lead inventor of the e-Puzzler. "Our task is now to make the technology applicable for huge masses of data. The biggest challenge is the scanning technology — we are working on the cutting edge of what is possible in that field." But even after the documents are put back together, it could take years before we understand their place in history. "Once assembled, the digital pages need to be reviewed for plausibility before the Stasi record office can even start to reassemble files and folders from the reconstructed pages, let alone study and process the information," says Nickolay.

The Fraunhofer Institute will complete the government-funded $8.5 million pilot stage of its e-Puzzler project by late next year. In 2012, the German parliament will decide how much future funding to give the project, if any at all.

Even before the new machine is up and running, the impact it could have on Germany's sense of history — and Germans' sense of themselves — is clear. Almost two decades after German reunification, hardly a month goes by without a lawmaker, sports coach or newspaper editor being identified as a former Stasi spy. The information revealed in those reconstructed files could end careers, or allow people suspected of having spied to finally prove their innocence. And many victims of the Stasi still wonder who destroyed their careers, or why they ended up in prison. Nickolay himself is partly driven by the desire to find out the truth behind the imprisonment of his friend Jürgen Fuchs, a leading GDR opposition figure who was exposed to radiation during his captivity and later died of leukemia. "It has never been uncovered who the mastermind behind all this was, and who gave the orders to harm my friend," says Nickolay. "The reconstruction of the files may well give us the clues."

For Joachim Häussler, project head at the federal government agency that is restoring the shredded Stasi records, the e-Puzzler offers Germans a chance to take back a part of their history that was hidden from them — one small piece at a time. "We owe it to future generations to decipher this heritage," he says. "And we have the unparalleled chance to analyze the workings of a secret service. Now, where else in the world do you get to do that?"

• Claudia Himmelreich / Berlin
• Using brand new software and cutting-edge technology, scientists in Germany hope to reconstruct thousands of files that were shredded by the secret police at the end of the Cold War