http://www.eff.org/news/archives/2005_10.php#004063
Secret Code in Color Printers Lets Government Track You
Tiny Dots Show Where and When You Made Your Print
San Francisco - A research team led by the Electronic Frontier
Foundation (EFF) recently broke the code behind tiny tracking dots that
some color laser printers secretly hide in every document.
The U.S. Secret Service admitted that the tracking information is part
of a deal struck with selected color laser printer manufacturers,
ostensibly to identify counterfeiters. However, 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.
You can see the dots on color prints from machines made by Xerox, Canon,
and other manufacturers (for a list of the printers we investigated so
far, see: http://www.eff.org/Privacy/printers/list.php). 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 (for instructions on how
to see the dots, see: http://www.eff.org/Privacy/printers/docucolor/).
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 at http://www.eff.org/Privacy/printers/doc ... hp#program.
Xerox previously admitted that it provided these tracking dots to the
government, but indicated that only the Secret Service had the ability
to read the code. The Secret Service maintains that it only uses the
information for criminal counterfeit investigations. However, there are
no laws to prevent the government from abusing this information.
"Underground democracy movements that produce political or religious
pamphlets and flyers, like the Russian samizdat of the 1980s, will
always need the anonymity of simple paper documents, but this technology
makes it easier for governments to find dissenters," said EFF Senior
Staff Attorney Lee Tien. "Even worse, it shows how the government and
private industry make backroom deals to weaken our privacy by
compromising everyday equipment like printers. The logical next question
is: what other deals have been or are being made to ensure that our
technology rats on us?"
EFF is still working on cracking the codes from other printers and we
need the public's help. Find out how you can make your own test pages to
be included in our research at
http://www.eff.org/Privacy/printers/wp.php#testsheets.
Contact:
Seth Schoen
Staff Technologist
Electronic Frontier Foundation
seth@eff.org
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