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http://events.ccc.de/congress/2011/Fahrplan/events/4780.en.html http://events.ccc.de/congress/2011/Fahrplan/events/4780.en.h... Appears to have the materials f

by timtadh 15y ago

http://events.ccc.de/congress/2011/Fahrplan/events/4780.en.html http://events.ccc.de/congress/2011/Fahrplan/events/4780.en.h... Appears to have the materials from the talk. Most interesting bit from the researcher's write up: "We have also unpacked several engine-control processor firmwares (different from the main SoC) and are currently attempting to locate code related to tracking dots. Perhaps we will have some results by December. In any case, HPacker will help the community to do further research in this direction, possibly allowing us to spoof / disable these yellow dots of burden." In case people are not aware of the background, most printers print special patterns of "invisible" dots on every sheet printed. This allow the printed pages to be tied directly to the printer which printed the dots. Thus, if you are printing something like a political flyer which is inconvenient to your government, the government may be able to tie the flyer to you using these dots.

larrys 15y ago
"most printers print special patterns of "invisible" dots on every sheet printed" I believe this is only relevant to color printers since black pixels would be noticeable. Additionally if you were to copy/scan the document (even in color) you could alter the imaging to yield no yellow dots by exposure or contrast settings (this is common in the printing industry). Also, this assumes that the serial number of the printer is registered. While it would be possible with an extensive search to locate the buyer of a particular printer even if they didn't register the machine (by tracing to a particular dealer etc.) unless you were committing a major crime (like counterfeiting for example) this doesn't seem like something worth the effort or practical in most cases. You could also alter the printer to add additional yellow dots to confuse any interpretation. http://w2.eff.org/Privacy/printers/docucolor/ http://w2.eff.org/Privacy/printers/docucolor/
- Maxious 15y ago
  In more recent news, a team in the DARPA shredded document reassembly challenge based one of the hardest solutions in part on correctly placing pieces based on those yellow dots... which they learned about on hacker news :) http://news.ycombinator.com/item?id=3368611 http://news.ycombinator.com/item?id=3368611

by timtadh 15y ago

larrys 15y ago

"most printers print special patterns of "invisible" dots on every sheet printed" I believe this is only relevant to color printers since black pixels would be noticeable. Additionally if you were to copy/scan the document (even in color) you could alter the imaging to yield no yellow dots by exposure or contrast settings (this is common in the printing industry). Also, this assumes that the serial number of the printer is registered. While it would be possible with an extensive search to locate the buyer of a particular printer even if they didn't register the machine (by tracing to a particular dealer etc.) unless you were committing a major crime (like counterfeiting for example) this doesn't seem like something worth the effort or practical in most cases. You could also alter the printer to add additional yellow dots to confuse any interpretation. http://w2.eff.org/Privacy/printers/docucolor/ http://w2.eff.org/Privacy/printers/docucolor/

Maxious 15y ago
In more recent news, a team in the DARPA shredded document reassembly challenge based one of the hardest solutions in part on correctly placing pieces based on those yellow dots... which they learned about on hacker news :) http://news.ycombinator.com/item?id=3368611 http://news.ycombinator.com/item?id=3368611