Stasi officers managed to tear up some 48 million pages filling over 16,000 brown sacks - each containing up to 40,000 shreds of paper. Together with about 112 kilometers (70 miles) of files that the Stasi was unable to destroy, they constitute a vast, but probably incomplete, catalog of mundane observations and cruel repression spanning 40 years.

But piecing all the bits together would, by some estimates, have taken 800 years.

In an effort to speed up the process historians and scientists from the nearby Fraunhofer Institute for Production Systems and Design Technology devised a method that allows computers to scan pre-sorted shreds and automatically find bits that match.