CSC 379 SUM2008:Week 4, Group 4

Printer Tracking Technology

How does it work?

Encoding data in the form a machine-readable printed graph is not a new idea—adhering printed barcodes to physical objects for tracking purposes has been a commercial practice since 1966, becoming truly ubiquitous in the 1980s. [1] Printer tracking codes are a lot like commercial UPC codes, except that they are virtually undetectable by unaided human eyes and data is encoded into a 2-Dimensional array of micro-dots. As an example, the Xerox DocuColor series printer encodes printer data into a 15x8 grid of nearly invisible yellowish dots. The grid is repeated across the entire page, so even fragmented documents may later be forensically identified. The data encoded by the printer is simple: the printer's serial number, the date and time at which a document was printed.

Currently, hidden printer tracking technology has been found only in some laser printers, of which EFF has compiled a non-comprehensive list.

Why Is It Useful?

Currently, the only official use of the hidden tracking dots by our government is their role in tracking down counterfeiters. These criminals often employ the technique of scanning legal currency, then by using a color laser printer or color laser copier, they are able to mass-produce the counterfeit money that is of a high enough quality that it will fool most people. By using the hidden tracking codes, law-enforcement officials, specifically the Secret Service, are able to determine the brand and model number of the printer that produced the counterfeit bills as well as finding the specific serial number of the offending machine. They are then able to use that information to contact the manufacturer of the printer to gain purchase information that will allow them to determine who owns that specific device.

Currency counterfeiters are not the only ones affected by this technology. By employing similar criminal techniques, document forgers are using color printers to forge driver's licenses, passports, identification badges, and checks. By analyzing the tracking dots on the paper that the forged documents were printed on, authorities are able to create a paper trail leading to the forgers and expedite their capture.

This practice is not limited the the United States government as the governments of other countries concerned with the circulation of counterfeit currency also employ the same techniques used by the Secret Service.

Is it a bad idea?

By producing what amounts to a documented signature of the originating machine, the anonymity that comes from a printed document over a digital document is no longer possible due to this technology. There is nothing about this technology that limits its use to only tracking counterfeiters and forgers so the end result is that it is a blatant violation of the privacy of the affected person, even when they are not guilty of any crimes. Otherwise innocent people such as political dissidents, whistleblowers, religious activists, or protesters that certain groups might find threatening can be tracked due to their privacy being compromised by their printers. This seemingly blatant privacy violation is not going unchallenged as groups in the United States and Europe are pressing their governments to act and defend their rights to privacy. While it's original design was a noble one, the end result is that these document tracking dots remove any sense of privacy for the author of a document and might as well be the signature of that author.

Links

• Government Uses Color Laser Printer Technology to Track Documents. Jason Tuohey, Medill News Service. Nov 22, 2004.
• Printer dots raise privacy concerns. Thomas Frank, USA Today. Jul 13, 2008.
• EFF's analysis of Xerox DocuColor Printers' hidden printer tracking dots.
• EFF's list of laser printers that do or do not display tracking dots.