U.S. Secret Service and Xerox covertly track documents

The Electronic Freedom Foundation (EFF)has cracked the code used to secretly tag documents printed by color laser printers.

"At the request of the United States Secret Service, manufacturers developed mechanisms that print in an encoded form the serial number and the manufacturer's name as indiscernible markings on color documents," the EFF's white paper says.

The secret markings can be found by anyone with a blue light and a magnifying glass. The design makes it easy for governments, or anyone else to spy. Since anyone with common tools can view the printer's encoding, it could put important anonymous speech at risk. One can imagine a scenario in which one person creates two documents one with that person's name on it and the other anonymous. If another individual were to use a blue light to compare the two documents, the anonymity of the second document would disappear. That could be bad in a business setting or from an anonymous political speech point of view.

The EFF said it has identified similar coding on pages printed from virtually every major printer manufacturer though it has so far managed to crack the codes for only one Xerox model.

Seth David Schoen, staff technologist, EFF, said that the dots are yellow, less than one millimeter in diameter, and are typically repeated over each page of a document. The pattern is visible under blue light with the help of a magnifying glass or a microscope.

A complete list of the printers that have the yellow dots is given here. www.eff.org/Privacy/printers/list.php. Though some printers do not produce the yellow dots, some of them leave other watermarks and may have other ways of identifying them.

The time, money, and ingenuity that went into the printer-spy caper would be better spent in ways that actually catch criminals and terrorists without endangering key liberties.

Picture is a close up of actual tracking dots, taken through a microscope, dot size 1mm apx