Picking Up the Pieces

[InfoSec News <isn () c4i org>]

http://www.nytimes.com/2003/07/17/technology/circuits/17shre.html

By DOUGLAS HEINGARTNER
July 17, 2003   

BERLIN -- 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.

"It's more than just the algorithms about the puzzles," said Bertram
Nickolay, the head of the security and testing technologies
department. Indeed, the archive is a massive grab bag of randomly torn
documents, many with handwritten and typewritten text on the same
page. Combining all these technologies in a project of this scope "is
on the borders of what's possible," Mr. Nickolay said.

His system's accuracy rate is about 80 percent. "It will take time for
the algorithms to be optimized," Mr. Nickolay said, noting that
handwriting analysis began with accuracy levels of around 50 percent,
and are now at 90 percent and above.

Some of the companies competing for the job concentrated on the shape,
color and perforations of the shreds, while other contenders opted for
semantically driven systems, which looked for keywords and likely text
matches.

The Fraunhofer plan is to combine its smart scanning software with the
know-how of the Zirndorf archivists, who have amassed years of
experience working with these tiny pieces of history. After all the
shreds have been scanned (at 200 dots per inch), the interactive
software will suggest possible matches, which an operator can accept
or reject.

While Fraunhofer IPK eventually plans to use a similar technique,
several companies say they can do so already.

ChurchStreet's software 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 shreds for possible
matches.

Mr. Ford, the company founder, said the ChurchStreet service can
recover up to 70 percent of a document's content, although he stressed
that the goal was to get blocks of information rather than to
re-create the original formatting. The blocks are presented to the
client, who determines where they might belong in the overall scheme.  
"We don't make any guesswork about reconstruction," Mr. Ford said. "We
make no assumptions."

ChurchStreet, whose clients are mainly law agencies and private law
firms, charges roughly $2,000 to reconstruct a cubic foot of
strip-shreds. A cubic foot of shreds is generally less than 100 pages.  
Mr. Ford said ChurchStreet would soon offer a service to reconstruct
cross-shredded documents - that is, those cut in two directions - for
$8,000 to $10,000 per cubic foot. A common standard in cross-shredding
is particles one thirty-second by seven-sixteenths of an inch, which
results in thousands of grain-like shreds per page.

Cross-shredding makes the job a lot trickier, but not for lack of
processing power. "The problem is not whether it's possible with the
software, which is possible," said Werner Vögeli, the managing
director of the German office of SER Solutions, a company in Dulles,
Va., that also competed for the contract to reconstruct the Stasi
documents. "The problem is how to scan these documents."

Fred Cohen, a security consultant who reconstructed many pages while
working at Sandia National Laboratories, also sees limits. "When you
get down to very small shreds, then the numbers start to eat you," he
said. "You start to get to where there isn't enough text per shred to
be of any use. You've got a completely black shred; whether it's the
middle of the cross of a t or the dot of an i, you can't tell."

Adding to the challenge, the smaller the pieces are, the farther apart
they can fall, and thus the less likely they are to cluster in a
conveniently retrievable form. Security experts also say that using
large type (for less text per shred), and feeding the paper into a
shredder perpendicular to the direction of the text (so no complete
phrases stay together) makes shredding less vulnerable.

Professional document reconstructions are generally recognized by the
courts in much the way that fingerprint or handwriting evidence is. An
expert may not be able to vouch for the accuracy of the information on
a given page, said Mr. Daly, the former F.B.I. investigator, but he
can testify that a reconstructed document "was at one time one piece
of paper that was cut into little pieces of paper, and now it's back
into one piece of paper."

Mr. Daly added that investigators often use reassembled pages as part
of a larger forensic puzzle. "Once we have a hard-copy document, we
can then go back and look at databases and put in search criteria, and
to be able to actually come up with the original electronic version,"  
he said. "One becomes a pathway to the other."

The demand for such investigative services is clear. "I probably get a
call every month," said Robert Johnson of the National Association for
Information Destruction, an American trade group, from clients looking
for "a way to reverse the process."

Other projects, like Mr. Brassil's at Hewlett-Packard, focus on
designing a shredder that leaves telltale traces on the documents it
destroys, allowing them to be pinpointed later.

In Germany, meanwhile, a decision about whether to proceed with the
reconstruction of Stasi documents is not expected before September.  
Mr. Vögeli of SER Solutions, whose firm withdrew from bidding for the
project, said he doubted that financing would materialize. "These
documents contain lots of information that might be dangerous to a few
politicians who are still active, still in power," he said. "So
there's no political majority for any such investment."

Sascha Anderson, the dissident discredited by the files, is among
those who hope the project goes forward. "Of course I would have
preferred that they weren't found," he said by phone from Frankfurt.  
"But I realize that it's a unique chance for a society to have access
to this information."

And since he was exposed, he said, he has been able to sleep better:  
"I've ultimately been freed of my burden by history."



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