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The big reveal in 2024! Why is every color laser printer secretly recording your printing traces?
With the advancement of digital technology, many people use color laser printers to print daily documents. What is not well known is that these printers actually leave behind hidden traces of each page they print—the so-called “print tracking dots.”
These tracking dots are a type of digital watermarking technology originally developed by Xerox and Canon in the mid-1980s to prevent counterfeiting of banknotes.
History of Tracking Points
In the mid-1980s, Xerox pioneered an encoding mechanism that used tiny dots to convey unique device numbers, first used in its DocuColor line of printers. The technology is designed to "alleviate concerns that its color copiers could be used to counterfeit currency," and has been granted a U.S. patent. This tracking system was subsequently widely used in printers from other manufacturers.
The secret tracking scheme was not made public until October 2004, when Dutch authorities tracked down counterfeiters using Canon color laser printers. Subsequently, many media reports pointed out that this tracking mechanism has existed for decades and can help law enforcement agencies identify and track counterfeiting activities.
Technical Details
These tracking dots consist of tiny yellow dots that are barely visible to the naked eye, approximately 0.1 mm in diameter, and are evenly spaced across the printed page. The dots are arranged in a way that actually encodes the serial number, date and time of the printing device, and are repeated multiple times across the printing area to prevent errors.
According to a 2005 study, a color printer stores 64 bytes of information in a 32 x 16 dot matrix, which can be repeated up to 150 times.
These trace points can be analyzed even if only fragments or parts of the document are available. The study found that these arrangements are very complex and may be more diverse among printers of different manufacturers and models.
Visibility
These tracking points can be viewed with a high-resolution scanner and displayed by enhancing the yellow channel in an image processing program. Under good lighting conditions, these patterns can even be seen with a magnifying glass. Under ultraviolet light, these yellow dots are even more clearly visible.
Such covert marking technology could be used to track down high-quality reproductions, such as counterfeit banknotes, and would be identifiable even among fragments of the document.
Practical Applications
Analysts pointed out that the well-known media "Intercept" accidentally disclosed confidential information with printed tracking points when handling the information of whistleblower Reality Winner, which eventually led to her arrest and conviction. .
Privacy protection and avoidance techniques
Documents containing private or sensitive personal information, whether it's health records, account statements or even tax declarations, could be traced back to the printer's owner through these tracking points. Many users are unaware of this, and manufacturers do not release the code that generates these modes.
The Electronic Frontier Foundation (EFF) attempted to reveal how to decode these tracepoints as early as 2005, and provided a Python script to assist in the analysis.
Researchers have developed a method to overlay additional yellow dots on printed tracking dots to hide the original tracking information, helping whistleblowers protect their identities when exposing injustices.
Questions yet to be explored
Although the European Parliament discussed the issue of privacy invasion in 2007, there has been no consensus on the visibility of this technology and its impact on personal privacy. What’s more, as technology continues to evolve, we cannot be sure whether new covert tracking technologies will emerge.
Every printed product may invisibly record our whereabouts and history. Today, do you still dare to use a color laser printer to print sensitive documents at will?
