Yellow dots

A Machine Identification Code (MIC), also known as printer steganography, yellow dots, tracking dots or secret dots, is a digital watermark which certain color laser printers and copiers leave on every single printed page, allowing identification of the device with which a document was printed and giving clues to the originator. Developed by Xerox and Canon in the mid-1980s, its existence became public only in 2004. In 2018, scientists developed privacy software to anonymize prints in order to support whistleblowers publishing their work. In the mid-1980s Xerox pioneered an encoding mechanism for a unique number represented by tiny dots spread over the entire print area. Xerox developed the machine identification code 'to assuage fears that their color copiers could be used to counterfeit bills' and received U.S. Patent No 5515451 describing the use of the yellow dots to identify the source of a copied or printed document. In October 2004, consumers first heard of the hidden feature, when it was used by Dutch authorities to track down counterfeiters who had used a Canon color laser printer. In November 2004, PC World broke the news that this machine identification code had been used for decades in some printers, allowing law enforcement to identify and track down counterfeiters. The Central Bank Counterfeit Deterrence Group (CBCDG) has denied that it developed the feature. In 2005, the civil rights group Electronic Frontier Foundation (EFF) encouraged the public to send in sample printouts and subsequently decoded the pattern. The pattern has been demonstrated on a wide range of printers from different manufacturers and models. The EFF stated in 2015 that the documents that we previously received through FOIA suggested that all major manufacturers of color laser printers entered a secret agreement with governments to ensure that the output of those printers is forensically traceable. In 2007, the European Parliament was asked about the question of invasion of privacy. The pattern consists of a dot-matrix spread of yellow dots, which can barely be seen with the naked eye. The dots have a diameter of a tenth of a millimeter (0.004') and a spacing of about one millimeter (0.039'). Their arrangement encodes the serial number of the device, date and time of the printing, and is repeated several times across the printing area in case of errors. For example, if the code consists of 8 × 16 dots in a square or hexagonal pattern, it spreads over a surface of about 4 square centimetres (0.62 sq in) and appears on a sheet of size DIN-A4 paper about 150 times. Thus, it can be analyzed even if only fragments or excerpts are available. Some printers arrange yellow dots in seemingly random point clouds. According to the Chaos Computer Club in 2005, color printers leave the code in a matrix of 32 × 16 dots and thus can store 64 bytes of data (64×8).