Unshredding the Evidence (Spring, 1996) --------------------------------------- By Datum Fluvius The key to reconstructing shredded documents is to sort the shreds prior to paste-up. There are so many differences in the angle of each shred, what text each document contained, which color its paper was, and which weight, that the identification of individual documents by their shreds is fairly simple. It is, of course, tedious. It also takes practice. But once the shreds have been properly classified, only a few pages exist in each little group of sorted shreds. These will submit easily to careful paste-up and reconstruction, since only one or two hundred shreds exist in a three-page group of average size. (This article assumes you are not dealing with cross-cut, chipped documents, or ashes, but with "paper spaghetti.") A three-page group only takes an hour or two to completely reconstruct. The key to paste-up, in turn, is proper and systematic comparison of each and every shred against as many others as seem to fit. This has to be done systematically in order to avoid recomparisons, and to identify patterns in the reconstructed portions. The Procedure Place the sorted shreds into a "raw" area to one side, and place the first shred on the paste-up board, anywhere. (Tape it down with masking tape, top and bottom. Masking tape pulls back off the board easier than clear tape.) Next, pick up the second shred, and place it alongside the first in the same orientation. Compare it against one side, then the other. If it matches, tape it down, and if it does not, tape it down a little farther away, perhaps an inch or so away, parallel to the first. Repeat, repeat, repeat. Uncrook your back every little while. When you compare the shreds in this manner, you are limiting the number of comparisons to a fixed, predictable number. If you run out of room to paste down new strips, grab a fresh paste-up board and keep it handy or prepare to recycle the "no-match" pile, which will develop opposite the raw pile. But that adds steps, and time, to your task. Inspect the reconstructed document strips as they grow. Read what develops to guess which shreds match the open edges. The widening strips are compared as if they were shreds, and joined whenever possible. If two matching strips coexist on a pasteup board but remain unjoined, they retard your further comparisons since two of the available edges will not match any free shreds. That also wastes time. When a few documents have been completed, transparent packing tape can be used to fuse them, or care can be taken to tape only the tops and bottoms of each document with masking tape. That way, when the shreds are cut free of their tape, they are just a bunch of loose shreds again, ready for disposal. Clear contact paper has been used, but it can ruin documents whose shreds will not lay flat anymore due to dampness or lengthy storage. Tape is easier to control than contact paper, but both media will pull shreds up with their static electric charges unless you ground them. Fully taped documents are much easier to store and preserve, if you need the original. If you want the data, invest in photocopies. Press completed documents between plastic (overhead projector) sheets to keep the copier's glass clean and to align the shreds. One thing to remember is that businesses and governments use forms whenever possible to save cost. These can be road maps to incomplete reconstructed documents, and are invaluable to have prior to beginning a project. If need be, clear plastic can be traced over a completed form to outline just the form boxes. When laid over the partial document, these give a clue to what information is missing, and what shred patterns to look for to complete it. Obviously there are many uses for such a simple technique, even in this "information age" of the brave new world order. But it isn't foolproof. You may see coffee grounds mixed in with the bag, used cat litter, and even lunch waste mixed with the shreds. The targets who do that are probably well aware of this reconstruction technique, and will expect your forays into their dumpster. Their other main defense, subterfuge and decoy, is even more effective. They simply increase the shred volume to include everything available, and overflow the sorting capacity of the reconstructionist. Or they salt the real shredded information with errors and omissions, even fake derogatory documents, to elicit a revealing admission from the snoop. Burning is best, but is not legal in many urban areas. Even when it's legal, it's expensive; it requires safety equipment and personnel supervising every moment of the burn. The military, however, prefers fire and flushing to any alternative. When it absolutely, positively has to disappear overnight, fire and water should be your choice, too. Extra Assignment for the Artful Programmer Who needs this headache and tedium? Anyone who needs the data would have to give up their job or their social life to have time for reconstruction! Why not let a computer do it? Of course, feeding the data in is now easy with a flatbed scanner, and can be easier if you have thin sheets of clear, stiff plastic to sandwich/mash the shreds down. A programmer would then want to compare the edges of the images in the computer's memory. The basic idea is to turn the edge of a shred image into a "word" according to its pixel pattern. This word would then be sorted with the other words and the results would indicate which images are matches. Only a small portion of each edge would be compared, since a close match in one area is a good indicator for the whole. A sample size might be three inches in length, starting one inch down from the top of each shred. Reconstruction would be accomplished by drawing in the images in their relative positions and printing the result, or passing the image to an OCR routine for translation into completed ASCII text pages. Have fun, but publish your results!