ERLIN -- THROUGHOUT the 1980's, Sascha Anderson, a poet, musician and literary impresario, was one of the leading voices to speak out against the East German government and its dreaded secret police, the Stasi.

But his credibility gradually evaporated after the Communist government's collapse as rumors about him acquired the weight of proof: he had been informing on his dissident compatriots all along.

He had been told that his Stasi file had been destroyed. In fact, it was manually reconstructed from some of the millions of shreds of paper that panicked Stasi officials threw into garbage bags during the regime's final days in the fall of 1989.

Now, if all goes as planned by the German government, the remaining contents of those 16,000 bags will also be reconstructed.

Advanced scanning technology makes it possible to reconstruct documents previously thought safe from prying eyes, sometimes even pages that have been ripped into confetti-size pieces. And although a great deal of sensitive information is stored digitally these days, recent corporate scandals have shown that the paper shredder is still very much in use.

"People perceive it as an almost perfect device," said Jack Brassil, a researcher for Hewlett-Packard who has worked on making shredded documents traceable. If people put a document through a shredder, "they assume that it's fundamentally unrecoverable," he said. "And that's clearly not true."

In its crudest form, the art of reconstructing shredded documents has been around for as long as shredders have. After the takeover of the United States Embassy in Tehran in 1979, Iranian captors laid pieces of documents on the floor, numbered each one and enlisted local carpet weavers to reconstruct them by hand, said Malcolm Byrne of the National Security Archive at George Washington University. "For a culture that's been tying 400 knots per inch for centuries, it wasn't that much of a challenge," he said. The reassembled documents were sold on the streets of Tehran for years.

That episode helped convince the United States government to update its procedures for destroying documents. The expanded battery of techniques now includes pulping, pulverizing and chemically decomposing sensitive data. Yet these more complex methods are not always at hand in an emergency, which is why the vagaries of de-shredding will be of interest to intelligence officials for some time to come.

"It's been an area of interest for a very long time," said William Daly, a former F.B.I. investigator who is a vice president at Control Risks Group, a security consulting firm. "The government is always trying to keep ahead of the curve."

Like computer encryption and hacking, "it's kind of a cat-and-mouse game, keeping one step ahead," he said. "That's why the government is always looking at techniques to help them ensure their documents are destroyed properly."

Modern image-processing technology has made the rebuilding job a lot easier. A Houston-based company, ChurchStreet Technology, already offers a reconstruction service for documents that have been conventionally strip-shredded into thin segments. The company's founder, Cody Ford, says that reports of document shredding in recent corporate scandals alerted him to a gap in the market. "Within three months of the Enron collapse at end of 2001, we had a service out to electronically reconstruct strip shreds," he said.

The Stasi archives are a useful reference point for researchers tackling the challenge, though perhaps more for the scale than the sophistication of the shredding. Most of the Stasi papers were torn by hand because the flimsy East German shredding machines collapsed under the workload. The hastily stored bags of ripped paper were quickly discovered and confiscated.

In 1995 the German government commissioned a team in the Bavarian town of Zirndorf to reassemble the torn Stasi files one by one. Yet by 2001, the three dozen archivists had gone through only about 300 bags, so officials began a search for another way to piece together the remaining 33 million pages a bit faster.

Four companies remain candidates for the job, including Fraunhofer IPK of Berlin, part of the Fraunhofer Gesellschaft research institute, which helped develop the MP3 music format. The institute is drafting plans to sort, scan and archive the millions of pages within five years, drawing on expertise in office automation, image processing, biometrics and handwriting analysis as well as sophisticated software.