Yellow dots identify printers: Computer scientists of TU Dresden develop a tool for printer anonymisation

Tracking dots are tiny, yellow dots that are invisible to the naked eye, but automatically included into almost all color prints. Their patterns identify the manufacturer, serial number of the printer, as well as the date and time of printing.

Analysing these tracking points, Timo Richter and Stephan Escher of the Chair of Privacy and Security found previously unknown pattern types. Based on a sample of 1286 prints from 141 printers from 18 different manufacturers (partially provided by the German DFKI, who studied these artifacts in 2005) they where able to develop an app that automatically decodes, which information has been embedded in the print. It can also be used to anonymize the prints, by scrambling the yellow dot patterns.

There exists no official information about reasons and the technology behind this tracking technology. Asked by the researchers, most companies denied comment, one suggested contacting the German Federal Bank and the Central Bank Counterfeit Deterrence Group, which both could not provide any insights. The tracking points seemingly are used for law enforcement, and, probably more importantly, to identify whistleblowers. The case of Reality Leigh Winner in 2016 is one such incident in which the former contractor of the NSA allegedly leaked classified material, and reportedly was identified and convicted based on the yellow dots included in the leaked printouts.

The dots have also been discussed by the European Parliament, which concluded that they "might violate the right to protection of personal data".

"We believe that citizens should be aware of the existence of such codes, and the surveillance that they make possible", said Escher. "The GDPR governs the protection of digital data, but only few people know that they can be observed and identified also with non-digital media".

"Every person should have the freedom of speech, which should also include uncovering unacceptable situations within companies or government bodies", adds Richter. For this purpose he developed the new app as part of his Master's thesis.

Richter presents his results at the ACM Information Hiding and Multimedia Security 2018, which takes place on June 21-22 in Innsbruck, Austria.

Informationen for journalists:
Prof. Thorsten Strufe
Tel.: +49 (0) 351 463-38247

News coverage regarding this paper:

• netzpolitik: https://netzpolitik.org/2018/gute-nachricht-fuer-whistleblower-dresdner-forscher-tricksen-druckerueberwachung-aus/
• heise: https://www.heise.de/newsticker/meldung/Dresdner-Forscher-ueberlisten-Tracking-Punkte-bei-Laserdruckern-4090876.html
• The Register: https://www.theregister.co.uk/2018/06/27/german_researchers_defeat_printer_tracking_dots/
• O'Reilly: https://www.oreilly.com/ideas/four-short-links-26-june-2018
• Deutschlandfunk: https://www.deutschlandfunk.de/farblaserdrucker-tracking-dots-unlesbar-machen.676.de.html?dram:article_id=421558
• Motherboard: https://motherboard.vice.com/de/article/3k438w/gelbe-punkte-drucker-verstecken-yellow-dots-muster-versteckte-botschaften
• Focus: https://www.focus.de/regional/dresden/technische-universitaet-dresden-geheime-daten-auf-dem-druckpapier_id_9134461.html
• Frankfurter Rundschau (via dpa): http://www.fr.de/leben/computer_internet/news/software-entwickelt-digitalen-fingerabdruck-in-farblaser-ausdrucken-zerstoeren-a-1533593
• Hamburger Abendblatt (via dpa): https://www.abendblatt.de/ratgeber/multimedia/article214702201/Digitalen-Fingerabdruck-in-Farblaser-Ausdrucken-zerstoeren.html
• ORF: http://orf.at/stories/2444683/
• Handelsblatt: https://www.handelsblatt.com/technik/thespark/digitalen-fingerabdruck-verraeterische-spuren-in-farblaser-ausdrucken-verwischen/22742154.html
• tweakers: https://tweakers.net/nieuws/140289/onderzoekers-maken-tool-om-prints-met-tracking-dots-te-anonimiseren.html

As well as several blogs (reddit, hacker news) and local media.