Printer Fingerprinting

tracking codes hidden in documents printed on Xerox color laser printers.

News came out a while ago that many of our laser printers were embedding “fingerprints” that allowed folks who knew how (like, say, the feds) to trace a printed page back to the day and time it was printed, and the serial number of the printer.

Or, at least that was the theory, until the EFF got all CSI on it. The image above is magnified 10x and illuminated with blue light to increase the contrast of the yellow dot pattern used by Xerox DocuColor printers. Some good reverse engineering efforts now allow folks to decipher those fingerprints, and the EFF even has a handy little form (go to the bottom of the page) to allow you to figure it out yourself.