Unshreddable How to reassemble a shredded document.

By Adrian Chen
Posted Friday, July 31, 2009, at 7:14 AM ET

Shredded documents Federal prosecutors told a judge last week that they have started reassembling documents shredded by the Stanford Financial Group, whose owner, R. Allen Stanford, is charged with running a $7 billion Ponzi scheme. How do you reconstruct documents after they've been passed through a shredder?
With a computer. In a typical reconstruction process, technicians feed all the available shreds into a scanner. An automated software program then assigns a unique ID to each piece and analyzes a number of characteristics, including size, color, indentation, and font. Using a matching algorithm, the software then identifies potential neighboring shreds, displaying them onscreen for an operator to confirm. For the home user, an Israeli company sells software that can turn any PC and scanner into an "unshredder."
Not all shredded documents can be put back together. The possibility and ease of reconstruction depends on the size of the shreds—the smaller and more numerous the pieces, the harder it is to reconstruct a document. Strip shredders cut paper into long strips 1/8- to 5/16-inch wide and are the most popular option because of their speed and low cost—but they're also the easiest to reassemble since they produce a relatively small number of large fragments. Cross-cut shredders, which slice paper into many tiny, confettilike pieces, are significantly more secure (and expensive), while shredders that pulverize paper into dust cost thousands of dollars but are essentially reconstruction-proof. (To secure top-secret information, the Department of Defense requires that the majority of shredded particles "not exceed 5 square millimeters.") When using a strip-shredder, the slicing direction also has implications for reconstruction. Horizontal cuts may leave entire lines of text intact. Vertical shredding, which ensures that sentences are broken up, is more secure.