Color printers leave a technical fingerprint that identifies the source of the document, silently encoding information about time and date of printing, and the printer’s serial number on every page printed.


Photo credit: Joăo Estęvăo A. de Freitas
The Electronic Frontiers Foundation recently released the results of the Machine Identification Code Technology Project, which dissects the technical details of the hidden coding system for at least one printer, revealing the simple mechanics that can leave a paper trail in more than one way.

Jason Tuohey documented this story last year in an article at PC World.com, and I wrote an article on this startling topic as well. This printer identification system has been in place for two decades now, and creates a valuable tool intended to bust counterfeiters, but is also a troubling notion for privacy advocates weary of big brother.

The EFF’s report reveals how Xerox DocuColor printers cover the entire page with a repeating grid of tiny yellow dots, invisible to the naked eye but easily visible under blue LCD flashlight. This grid is capable of encoding up to 14 seven-bit bytes of tracking information, presented in rows and columns of dots.

While the dots may appear confusing at first, once you know how to read the code, the identifying information is easily interpreted.

The cryptogram is relatively simple, and the EFF report includes a program that allows anyone to check the validity of this tracking system simply by entering the code from their printed page.

Users need only print a page on their color printer, look at it under a blue LCD, enter the coordination of dots into the program, and the system will tell you your printer’s serial number, the date and time printed – down to the minute.

This software is also available as an open source download, licensed under the GNU General Public License.

Not all color printers encode information in this way, and the EFF has included this list of printers that do not use the system of tiny yellow dots, but warns there may be other tracking techniques at work in those printers.

While the yellow dots system is alarming, its age and relative simplicity could indicate that it may have been replaced by a more sophisticated system that the public does not know about yet. This may be likely because now that the coding system is revealed, anyone could manipulate the marks using multiple printers.

Background

According to Tuohey’s article, this technology was pioneered about 20 years ago, “ to assuage fears that their color copiers could easily be used to counterfeit bills." This technology has since become common practice for most printer manufacturers around the world.

The encoder is buried deep in printers, and Tuohey warns that removing the tiny chip will likely just break the printer. “Standard mischief won't get you around it,," said Peter Crean, a senior research fellow at Xerox.

Lorelei Pagano, a counterfeiting specialist with the U.S. Secret Service told Tuohey the technology is extremely useful for tracing counterfeiters, and is not used to keep tabs on the public at large. "The only time any information is gained from these documents is purely in [the case of] a criminal act," Pagano said.

Nonetheless the above the EFF reports that “there are no laws to stop the Secret Service from using printer codes to secretly trace the origin of non-currency documents,” an alarming fact considering the wave of civil liberties-suppressing laws recently passed by many governments, such as the US Patriot Act.

According to the EFF, printer companies are also not required to inform customers if their printer uses any identification system.

Morale: Be careful on what you print and who you give it to. On that laser printout you just made there is your invisible signature on it.