For years, commercial printers have quietly inserted yellow dots into their output for the purpose of tracking which printer was used to create any document. The EFF publishes a howto guide for decoding your own printer. The purpose of the yellowdot software is simply to bring attention to the issue, and to thwart amateur attempts to use these yellow dots to breach privacy.
This software will create a PNG containing yellow dots that can then be overlaid onto existing printer output. These dots are randomly distributed across the image, and are therefore not useful for securely obfuscating the identity that is encoded within the printer’s generated dot pattern. However, “yellowdot” raises the amount of resources that must be expended to successfully identify the printer that generated a given document. It is hoped that “yellowdot” can be used to thwart amateur attempts to breach privacy, such as could conceivably be practiced in an office environment.
As reported by the Washington Post, the commercial printer yellow dot initiative has been endorsed in some capacity by the United States Secret Service for the purpose of thwarting currency counterfeiting. As of October 2008, there is no law that requires printers to generate yellow dots for any purpose, including identification purposes. This software is not intended to be used for committing fraud, and it is the belief of the author that this software, in fact, cannot be used for such purposes. By analyzing a sufficient sample of printer output, the “noise” that is generated by this program can be eliminated, and the original printer source can be reconstructed.