The EFF said on Tuesday that its researchers recently broke the code behind the tiny tracking dots, and said the US Secret Service confirmed that the tracking was part of a deal struck with selected colour laser printer manufacturers to identify counterfeiters.
“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 researcher Seth Schoen.
EFF said the yellow dots were less than one millimetre in diameter and could be seen only with a blue light, magnifying glass or microscope.
Lorie Lewis, a spokeswoman at the Secret Service, declined to confirm the report directly, but acknowledged that the agency “has worked together with other government agencies and industry on preventive technological countermeasures designed to discourage the illegal use of printers and copiers in the production of counterfeit currency”.
Lewis said she could not elaborate on these measures, but said they were “specific and limited to the reproduction of currency” and that the action “in no way tracks or measures the use of a personal computer’s hardware or software”.
EFF, a group promoting privacy, free speech and technological innovation, said the news had disturbing implications for privacy even if the aim was to stop counterfeiting.
EFF spokeswoman Rebecca Jeschke said the same information could be used by governments to track down dissidents.
“Internationally, there are governments who would be very interested in what dissidents have to say and in tracking dissidents,” she said.
Jeschke added that although the deal appeared to be with the US government, the fact that it was relatively easy to break the code would mean other governments could use the same codes for other purposes.
EFF broke a code in a Xerox DocuColor printer and identified other codes in printers from Canon, Brother, Dell, Hewlett-Packard, Epson and other makers.
And they noted that the codes are not limited to printers sold in the United States.
“We had test pages from Europe, and they do have the same codes on them,” Jeschke said.
Xerox spokesman Bill McKee said the company would not comment on specific technology “for security reasons”.
“Xerox does not routinely share any information about its customers,” he said. “We, like any manufacturer, assist investigating agencies, when asked.”
Beth Givens of the California-based Privacy Rights Clearinghouse said the report was troubling: “It begs the question about what other kinds of secret tracking mechanisms are out there,” she said.
Givens said the system could threaten a basic right to remain anonymous.
“The right to leaflet goes all the way back to the birth of this country,” she said. “If you print something on a colour printer, you’re no longer anonymous.
“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 attorney Lee Tien.
“Even worse, it shows how the government and private industry make backroom deals to weaken our privacy by compromising everyday equipment such as printers.
“The logical next question is: What other deals have been or are being made to ensure that our technology rats on us?”