Document shredders seem to work fine, as far as they go, but if you have serious need to destroy printed information, it may be necessary to take more drastic steps to thwart the brigades of phishers and espionage agents lurking around your rubbish bins.
Today’s invention is a machine which combines the following techniques to stop the revival of postmortem paperwork.
Imagine a printer which undertakes the security role of a shredder. (Actually, my current printer shreds quite a lot of the paper I feed into it, but that’s a different story). This device would overprint information appearing on a page. Since the ink itself is a major cost consideration, the overprinting wouldn’t be just a complete blacking out but would be targetted (using a simple lightbeam shone through the paper) at the edges between print and whitespace.
For a more sophisticated approach, a small scanner could be used to recognise page content and deal with each item more effectively. This would be driven by an inversion of OCR technology: if the machine has a model of what makes certain characters differentiable from others, it can mask those features preferentially.
Conventional shredders do a nice line in cutting paper into neat little strips. The cutters are pretty uniformly spaced, making it easier for determined miscreants to paste them back together. An alternative would be to do the cutting using a very fine waterjet (or even a laser). The advantage of this approach would be that just as with overprinting, the cutting could be directed so as to chop the paper in a content-dependent way. This would mean cutting long words into more fragments than short ones, for example.
A combination of content-dependent overprinting and cutting would obviously make reassembly that much more time consuming. Although this system would need to work one sheet at a time, at least it wouldn’t self destruct at the first sign of a residual staple.