Resurrecting shredded documents.

The documents you shred today may be reconstructed tomorrow.

In the fall of 1989, during the East German government's final hours, officers of its secret police, the Stasi, frantically threw millions of shredded documents into garbage bags. Now, according to the New York Times, the German government may reconstruct the contents of those 16,000 bags.

Crude ways to reconstruct shredded documents have been around for a while, but the technology has improved greatly. Advanced scanning technology makes it possible to reconstruct documents previously thought unreadable--sometimes even pages that have been ripped into confetti-size pieces. But although a large amount of sensitive data is increasingly stored digitally, recent corporate scandals have proved that shredders are still a critical method of destroying information.

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

Modern image-processing technology has made rebuilding shredded materials easier and taster. Fraunhofer IPK of Berlin, part of the Fraunhofer Gesellschaft Research Institute, drafted plans to sort, scan, and archive millions of pages of the Stasi files within five years, drawing on expertise in office automation, image processing, biometrics, and handwriting analysis, as well as sophisticated software. The task involves reassembling millions of documents--randomly torn by hand because the flimsy East German shredding machines could not handle the workload--many of which include both handwriting and typed text on the same page. Still, the accuracy rate is expected to be close to 80 percent.

This kind of service is not uncommon. There are companies that offer a reconstruction service for documents that have been conventionally strip-shredded into thin segments using software that analyzes the graphical patterns that go to the edge of each piece. First, workers paste the random shreds onto standard sheets of paper, which takes three to seven minutes per page. The pages are scanned, and software analyzes the pieces for possible matches. Up to 70 percent of a document's content can be recovered. A company in Houston offers this service and charges about $2,000 to reconstruct a cubic toot--less than 100 pages--of shredded strips. According to the Times, the company will soon offer a service to reconstruct cross-shredded documents for $8,000 to $10,000 per cubic foot.

Professional document reconstructions are generally recognized by the courts in much the same way that fingerprints or handwriting evidence is. According to security experts, using large type (less text per shred) and feeding the paper into a shredder perpendicular to the direction of the text makes reconstruction much more difficult, but probably not for long. Hewlett-Packard is designing a shredder that leaves telltale traces on the documents it destroys, allowing the pieces to be identified later.

Now more than ever, sensitive documents, shredded or not, can come back to haunt you.