How To Trace The Source of a Hard Copy

Good piece by AP on a Electronic Frontier Foundation report saying that tracking codes in color laser printers have been cracked. The report points to dots embedded in Xerox’s color laser printers that appear on the printed page, which can then be traced back to particular printers:

By analyzing test pages printed out by supporters worldwide and by staffers at various FedEx Kinko’s locations, researchers found that some of the dots correspond to the printers’ serial numbers. Other dots refer to the date and time of the printing.

This is done, AP says, to foil currency counterfeiters, but could just as easily be used by governments to track down criminals or dissidents. This is not just the typewriter trick, where a document could be traced back to a particular typewriter, or make of typewriter, by quirks in the typeface and letter alignment. Although that is a part of it: by comparing two documents it is possible to conclude they are from the same printer, which would poleax a suspect accused of being behind a document just by printing something from their printer.

But although the article doesn’t mention it, I assume these tracking codes could also allow people to track down a suspect, by looking at the serial number and following the distribution of that printer. Unless the purchaser chose to cover his tracks, it shouldn’t be too hard to trace the printer through the country, town, retailer and credit card receipt. (With the time stamp included, it should be possible to track down the customer even if the end user is in a public printshop.) I’m guessing here, but it all seems plausible.

It’ll be interesting to see where EFF goes with this. Me? I’m no dissident but I’m not crazy about anyone being able to trace back what I print out.