A technician painstakingly reconstructs torn files by hand. New digital methods will make this process easier and faster. *

Photo: Daniel Stier * View Slideshow Ulrike Poppe used to be one of the most surveilled women in East Germany. For 15 years, agents of the Stasi (short for Staatssicherheitsdienst, or State Security Service) followed her, bugged her phone and home, and harassed her unremittingly, right up until she and other dissidents helped bring down the Berlin Wall in 1989. Today, the study in Poppe's Berlin apartment is lined floor to 12-foot ceiling with bookshelves full of volumes on art, literature, and political science. But one shelf, just to the left of her desk, is special. It holds a pair of 3-inch-thick black binders — copies of the most important documents in Poppe's secret police files. This is her Stasi shelf.

Poppe hung out with East German dissidents as a teenager, got blackballed out of college, and was busted in 1974 by the police on the thin pretext of "asocial behavior." On her way out of jail, Stasi agents asked her to be an informant, to spy on her fellow radicals, but she refused. ("I was just 21, but I knew I shouldn't trust the Stasi, let alone sign anything," she says.) She went on to become a founding member of a reform-minded group called Women for Peace, and was eventually arrested 13 more times — and imprisoned in 1983 for treason. Only an international outcry won her release.

Poppe learned to recognize many of the men assigned to tail her each day. They had crew cuts and never wore jeans or sneakers. Sometimes they took pictures of her on the sidewalk, or they piled into a white sedan and drove 6 feet behind her as she walked down the street. Officers waited around the clock in cars parked outside her top-floor apartment. After one of her neighbors tipped her off, she found a bug drilled from the attic of the building into the ceiling plaster of her living room.

When the wall fell, the Stasi fell with it. The new government, determined to bring to light the agency's totalitarian tactics, created a special commission to give victims access to their personal files. Poppe and her husband were among the first people in Germany allowed into the archives. On January 3, 1992, she sat in front of a cart loaded with 40 binders dedicated to "Circle 2" — her codename, it turned out. In the 16 years since, the commission has turned up 20 more Circle 2 binders on her.

The pages amounted to a minute-by-minute account of Poppe's life, seen from an unimaginable array of angles. Video cameras were installed in the apartment across the street. Her friends' bedrooms were bugged and their conversations about her added to the file. Agents investigated the political leanings of her classmates from middle school and opened all of her mail. "They really tried to capture everything," she says. "Most of it was just junk."

But some of it wasn't. And some of it ... Poppe doesn't know. No one does. Because before it was disbanded, the Stasi shredded or ripped up about 5 percent of its files. That might not sound like much, but the agency had generated perhaps more paper than any other bureaucracy in history — possibly a billion pages of surveillance records, informant accounting, reports on espionage, analyses of foreign press, personnel records, and useless minutiae. There's a record for every time anyone drove across the border.

In the chaos of the days leading up to the actual destruction of the wall and the fall of East Germany's communist government, frantic Stasi agents sent trucks full of documents to the Papierwolfs and Reisswolfs — literally "paper-wolves" and "rip-wolves," German for shredders. As pressure mounted, agents turned to office shredders, and when the motors burned out, they started tearing pages by hand — 45 million of them, ripped into approximately 600 million scraps of paper.

There's no way to know what bombshells those files hide. For a country still trying to come to terms with its role in World War II and its life under a totalitarian regime, that half-destroyed paperwork is a tantalizing secret.

The machine-shredded stuff is confetti, largely unrecoverable. But in May 2007, a team of German computer scientists in Berlin announced that after four years of work, they had completed a system to digitally tape together the torn fragments. Engineers hope their software and scanners can do the job in less than five years — even taking into account the varying textures and durability of paper, the different sizes and shapes of the fragments, the assortment of printing (from handwriting to dot matrix) and the range of edges (from razor sharp to ragged and handmade.) "The numbers are tremendous. If you imagine putting together a jigsaw puzzle at home, you have maybe 1,000 pieces and a picture of what it should look like at the end," project manager Jan Schneider says. "We have many millions of pieces and no idea what they should look like when we're done."

As the enforcement arm of the German Democratic Republic's Communist Party, the Stasi at its height in 1989 employed 91,000 people to watch a country of 16.4 million. A sprawling bureaucracy almost three times the size of Hitler's Gestapo was spying on a population a quarter that of Nazi Germany.

Unlike the prison camps of the Gestapo or the summary executions of the Soviet Union's KGB, the Stasi strove for subtlety. "They offered incentives, made it clear people should cooperate, recruited informal helpers to infiltrate the entire society," says Konrad Jarausch, a historian at the University of North Carolina at Chapel Hill. "They beat people up less often, sure, but they psychologically trampled people. Which is worse depends on what you prefer."

That finesse helped the Stasi quell dissent, but it also fostered a pervasive and justified paranoia. And it generated an almost inconceivable amount of paper, enough to fill more than 100 miles of shelves. The agency indexed and cross-referenced 5.6 million names in its central card catalog alone. Hundreds of thousands of "unofficial employees" snitched on friends, coworkers, and their own spouses, sometimes because they'd been extorted and sometimes in exchange for money, promotions, or permission to travel abroad.

For such an organized state, East Germany fell apart in a decidedly messy way. When the country's eastern bloc neighbors opened their borders in the summer of 1989, tens of thousands of East Germans fled to the West through Hungary and Czechoslovakia. By autumn, protests and riots had spread throughout East Germany, with the participants demanding an end to restrictions on travel and speech. In the first week of October, thousands of demonstrators in Dresden turned violent, throwing rocks at police, who broke up the crowd with dogs, truncheons, and water cannons. The government described the thousand people they arrested as "hooligans" to state-controlled media.

But on October 9, the situation escalated. In Leipzig that night, 70,000 people marched peacefully around the city's ring road — which goes right past the Stasi office. Agents asked for permission from Berlin to break up the demonstration, but this was just a few months after the Chinese government had brutally shut down pro-democracy protests in Beijing's Tiananmen Square, to international condemnation. The East German government didn't want a similar bloodbath, so the Stasi did nothing. A week later, 120,000 people marched; a week after that, the number was 300,000 — in a city with a population of only 530,000.

In November, hundreds of East and West Berliners began dismantling the wall that bisected the city. But the communist government was still in power, negotiating with dissidents and hoping to hold on. Inside the Stasi, leaders hoped that if they weathered whatever changes were imminent, they'd be able to get back to business under a different name. But just in case, the head of the Stasi ordered the agency to start destroying the incriminating paperwork it had on hand.

In several small cities, rumors started circulating that records were being destroyed. Smoke, fires, and departing trucks confirmed the fears of angry Germans, who rushed in to their local Stasi offices, stopped the destruction, and spontaneously organized citizen committees that could post guards to secure the archives. Demonstrators spray-painted the walls with slogans like "The files belong to us" and "Stasi get out." Finally, on the evening of January 15, 1990, thousands of demonstrators pushed in the front gate of the Stasi's fortified Berlin compound.

At headquarters, agents had been more discreet than their colleagues in the hinterlands. Burning all those files would tip off angry Berliners that something was up. When the first destruction orders came in, they began stacking bags of paper in the "copper kettle," a copper-lined basement designed as a surveillance-proof computer room. The room quickly filled with bags of shredded and torn paper. Today, even the people gathering and archiving the Stasi files express grudging admiration for the achievement. "Destroying paper is shit work," says government archivist Stephan Wolf. "After two days your joints hurt. They ripped for two months."

But a few days after demonstrators breached the Stasi front gate, the archives still hadn't been found. A citizen group coalesced, determined to track them down. Among the searchers was a 23-year-old plumber named David Gill, a democracy activist barred from university because his father was a Protestant minister. He was secretly studying theology at an underground seminary in Berlin.

Accompanied by cooperative police, Stasi agents led Gill and his compatriots through twisting alleys and concrete-walled courtyards, all eerily empty. Finally they arrived at a nondescript office building in the heart of the compound. Inside, there was more paper than he had ever imagined. "We had all lived under the pressure of the Stasi. We all knew they could know everything," Gill says today. "But we didn't understand what that meant until that moment. Suddenly it was palpable."

Gill and his crew of volunteers preserved whatever they could, commandeering trucks and borrowing cars to collect files from Stasi safe houses and storage facilities all over Berlin. Most of it was still intact. Some of it was shredded, unrecoverable. They threw that away. But then there were also bags and piles of hand-torn stuff, which they saved without knowing what to do with it. "We didn't have time to look at it all," Gill says. "We had no idea what it would mean."

Bertram Nickolay grew up in Saarland, a tiny German state close to Luxembourg that is about as far from East Germany as you could go in West Germany. He came to West Berlin's Technical University in 1974 to study engineering, the same year Ulrike Poppe was placed under Stasi surveillance on the other side of the Berlin Wall. A Christian, he felt out of place on a campus still full of leftist radicals praising East German communism and cursing the US.

Instead, Nickolay gravitated toward exiled East German dissidents and democracy activists. "I had a lot of friends who were writers and intellectuals in the GDR. There was an emotional connection," he says.

Today, Nickolay is head of the Department of Security Technology for the Fraunhofer Institute for Production Systems and Design Technology. Fraunhofer is Europe's largest research nonprofit, with 56 branches in Germany alone and an annual budget of more than $1 billion. (Fraunhofer researchers invented the MP3 audio codec, which netted the society more than $85 million in license fees in 2006.)

In 1996, Nickolay saw a TV news report on an unusual project. A team working for the Stasi Records Office (BStU), the newly created ministry responsible for managing the mountain of paper left behind by the secret police, had begun manually puzzling together bags full of documents, scrap by scrap. The results were explosive: Here was additional proof that East Germany sheltered terrorists, ran national sports doping programs, and conducted industrial espionage across Western Europe. BStU's hand-assembly program also exposed hundreds of the Stasi's secret informants — their ranks turned out to include bishops, university professors, and West German bureaucrats.

But the work is painfully slow. Gerd Pfeiffer, the project's manager, says he and a dwindling staff have reassembled 620,500 pages of Stasi secrets in the 13 years since the project began. That works out to one bag per worker per year — 327 bags so far — and 700 years to finish.

That TV segment resonated with Nickolay — he had opposed the East German regime, and he had the necessary technical expertise. "This is essentially a problem of automation," he says, "and that's something Fraunhofer is very good at." He sent a letter to the head of BStU offering his help.

The government was hesitant, but eventually the BStU issued a proof-of-concept challenge: Anyone who could digitally turn 12 pieces of ripped-up paper into a legible document or documents would get a grant. About 20 teams responded. Two years later, Nickolay's group was the only one to succeed, earning a contract for a two-year, 400-bag pilot project.

On a gray day last fall, I sat in front of two wall-mounted Sharp Aquos flatscreen TVs hooked up to four networked computers. Next to me, Jan Schneider, Nickolay's deputy and the manager of the Stasi document reconstruction project, booted up the machines. (This was just a demo: Nickolay refused to show me the actual lab, citing German privacy law.)

On the right-hand screen, digital images of paper fragments appeared — technicians had scanned them in using a specially designed, two-camera digital imaging system. As Schneider pulled down menus and clicked through a series of descriptive choices, fragments disappeared from the screen. "Basically, we need to reduce the search space," he says. White paper or blue — or pink or green or multicolored? Plain, lined, or graph? Typewriting, handwriting, or both? Eventually, only a handful of similar-looking pieces remained. Once matched, the pieces get transferred to another processor. These popped up as a reconstructed page on the left-hand screen, rips still visible but essentially whole. (The reconstructors caught one big break: It turns out that the order-obsessed Stasi usually stuffed one bag at a time, meaning document fragments are often found together.)

Just 19 years old when the Berlin Wall fell, Schneider doesn't share Nickolay's moral outrage. For him, this is simply a great engineering challenge. He turns away from the massive monitors on the wall and picks up my business card to explain how the team is training the computers to look at these documents — the same way people do. "You see a white piece with blue writing on it — computer writing, machine writing, not handwriting — and here in the upper left is a logo. Tear it up and you'd immediately know what to look for, what goes together."

But my card is easy. For one thing, I sprang for heavy stock, and you'd be hard-pressed to tear it into enough pieces to constitute "destroyed." The Stasi files are something else entirely. In 2000, the BStU collected them and sent them to Magdeburg, a decaying East German industrial city 90 miles west of Berlin. In hand-numbered brown paper sacks, neatly stacked on row after row of steel shelves, they fill a three-story, 60,000-square-foot warehouse on the northern edge of town. Each sack contains about 40,000 fragments, for a total of 600 million pieces of paper (give or take a hundred million). And each fragment has two sides. That's more than a billion images.

The numbers aren't the worst part. The documents in the bags date from the 1940s to the 1980s, and they're made of everything from carbon paper and newsprint to Polaroids and heavy file folders. That means the fragments have a wide variety of textures and weights. Hand-ripping stacks of thick paper creates messy, overlapping margins with a third dimension along the edges. For a computer looking for 2-D visual clues, overlaps show up as baffling gaps. "Keep ripping smaller and smaller and you can get pieces that are all edge," Schneider says.

The data for the 400-bag pilot project is stored on 22 terabytes worth of hard drives, but the system is designed to scale. If work on all 16,000 bags is approved, there may be hundreds of scanners and processors running in parallel by 2010. (Right now they're analyzing actual documents, but still mostly vetting and refining the system.) Then, once assembly is complete, archivists and historians will probably spend a decade sorting and organizing. "People who took the time to rip things up that small had a reason," Nickolay says. "This isn't about revenge but about understanding our history." And not just Germany's — Nickolay has been approached by foreign officials from Poland and Chile with an interest in reconstructing the files damaged or destroyed by their own repressive regimes.

This kind of understanding isn't cheap. The German parliament has given Fraunhofer almost $9 million to scan the first 400 bags. If the system works, expanding up the operation to finish the job will cost an estimated $30 million. Most of the initial cost is research and development, so the full reconstruction would mainly involve more scanners and personnel to feed the paper in.

Is it worth it? Günter Bormann, the BStU's senior legal expert, says there's an overwhelming public demand for the catharsis people find in their files. "When we started in 1992, I thought we'd need five years and then close the office," Bormann says. Instead, the Records Office was flooded with half a million requests in the first year alone. Even in cases where files hadn't been destroyed, waiting times stretched to three years. In the past 15 years, 1.7 million people have asked to see what the Stasi knew about them.

Requests dipped in the late 1990s, but the Oscar-winning 2006 film The Lives of Others, about a Stasi agent who monitors a dissident playwright, seems to have prompted a surge of new applications; 2007 marked a five-year high. "Every month, 6,000 to 8,000 people decide to read their files for the first time," Bormann says. These days, the Stasi Records Office spends $175 million a year and employs 2,000 people.

This being Germany, there's even a special word for it: Vergangenheitsbewältigung, or "coming to terms with the past." It's not self-evident — you could imagine a country deciding, communally, to recover from a totalitarian past by simply gathering all the documents and destroying them. In fact, in 1990 the German press and citizen committees were wracked by debate over whether to do just that. Many people, however, suspected that former Stasi agents and ex-informants were behind the push to forgive and forget.

By preserving and reconstructing the Stasi archives, BStU staffers say they hope to keep history from repeating itself. In November, the first children born after the fall of the wall turned 18. Evidence suggests many of them have serious gaps in their knowledge of the past. In a survey of Berlin high school students, only half agreed that the GDR was a dictatorship. Two-thirds didn't know who built the Berlin Wall.

The files hold the tantalizing possibility of an explanation for the strangeness that pervaded preunification Germany. Even back then, Poppe wondered if the Stasi had information that would explain it all. "I always used to wish that some Stasi agent would defect and call me up to say, Here, I brought your file with me,'" Poppe says.

Reading the reports in that first set of 40 binders spurred her to uncover as much as she could about her monitored past. Since 1995, Poppe has received 8 pages from the group putting together documents by hand; the collection of taped-together paper is in a binder on her Stasi shelf.

The truth is, for Poppe the reconstructed documents haven't contained bombshells that are any bigger than the information in the rest of her file. She chooses a black binder and sets it down on the glass coffee table in her living room. After lighting a Virginia Slim, she flips to a page-long list of snitches who spied on her. She was able to match codenames like Carlos, Heinz, and Rita to friends, coworkers, and even colleagues in the peace movement. She even tracked down the Stasi officer who managed her case, and after she set up a sort of ambush for him at a bar — he thought he was there for a job interview — they continued to get together. Over the course of half a dozen meetings, they talked about what she found in her files, why the Stasi was watching her, what they thought she was doing. For months, it turned out, an agent was assigned to steal her baby stroller and covertly let the air out of her bicycle tires when she went grocery shopping with her two toddlers. "If I had told anyone at the time that the Stasi was giving me flat tires, they would have laughed at me," she says. "It was a way to discredit people, make them seem crazy. I doubted my own sanity sometimes." Eventually, the officer broke off contact, but continued to telephone Poppe — often drunk, often late at night, sometimes complaining about his failing marriage. He eventually committed suicide.

Poppe is looking forward to finding out what was in that last, reconstructed 5 percent. "The files were really important to see," she says, taking a drag on her cigarette and leaning forward across the coffee table. "They explained everything that happened — the letters we never got, the friends who pulled away from us. We understood where the Stasi influenced our lives, where they arranged for something to happen, and where it was simply our fault."

Andrew Curry (andrew@andrewcurry.com) is a journalist based in Berlin.

Feature Solving a Billion-Piece Puzzle