On the face of it, the U.S. Secret Service has stated that the tracking information is part of a deal struck with selected color laser printer manufacturers, ostensibly to identify counterfeiters. But in reality, the nature of the private information encoded in each document was not previously known. “We’ve found that the dots from at least one line of printers encode the date and time your document was printed, as well as the serial number of the printer,” said EFF Staff Technologist Seth David Schoen. Almost all major printer manufacturers like Xerox, Canon, Brother, HP, Dell, Lexmark etc. carry this secret code. You can find the list of printer manufacturers and the printer models which have these code here. EFF researchers say that users can see the dots on color prints from machines made by Xerox, Canon, etc. The dots are yellow, less than one millimeter in diameter, and are typically repeated over each page of a document. In order to see the pattern, you need a blue light, a magnifying glass, or a microscope. The researchers have given the instructions here on how to connect the dots. EFF and its partners began its project to break the printer code with the Xerox DocuColor line. Researchers Schoen, EFF intern Robert Lee, and volunteers Patrick Murphy and Joel Alwen compared dots from test pages sent in by EFF supporters, noting similarities and differences in their arrangement, and then found a simple way to read the pattern. “So far, we’ve only broken the code for Xerox DocuColor printers,” said Schoen. “But we believe that other models from other manufacturers include the same personally identifiable information in their tracking dots.” You can decode your own Xerox DocuColor prints using EFF’s automated program.
