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Researcher Wants To Protect Whistleblowers Against Hidden Printer Dots (bleepingcomputer.com)
An anonymous reader writes: "Gabor Szathmari, a security researcher for CryptoAUSTRALIA, is working on a method of improving the security of leaked documents by removing hidden dots left behind by laser printers, which are usually used to watermark documents and track down leakers," reports Bleeping Computer. "Szathmari's work was inspired by the case of a 25-year-old woman, Reality Leigh Winner, who was recently charged with leaking top-secret NSA documents to a news outlet." According to several researchers, Winner might have been caught after The Intercept had shared some of the leaked documents with the NSA. These documents had the invisible markings left behind by laser printers, which included the printer's serial number and the date and time when the document was printed. This allowed the NSA to track down Winner and arrest her even before she was able to publish the leaked documents. Now, Szatmari has submitted a pull request to the PDF Redact Tools, a project for securely redacting and stripping metadata from documents before publishing. Szathmari's pull request adds a code routine to the PDF Redact Tools project that would allow app operators to convert documents to black and white before publishing. "The black and white conversion will convert colors like the faded yellow dots to white," Szathmari said in an interview. Ironically, the project is managed by First Look Media, the parent company behind The Intercept news outlet.
Long before laser printers, investigators were tying people to typewriters based on unique per-unit imperfections and wear patterns. You can do something similar based on drum and toner distribution variances even on a monochrome non-watermarked printer.
Granted, the judas dots also report the date and time, which helps nail a culprit on a shared resource, but the safest thing to do would be to OCR the printed documents rather than photocopy them.
by removing hidden dots left behind by laser printers, which are usually used to watermark documents and track down leakers,
This is incorrect. The purpose of the dots and why they are limited to color printouts is because they are intended to be used to identify currency counterfeiters.
wiki
During the 1990s Xerox and other companies sought to reassure governments that their printers would not be used for forgery.
Anons need not reply. Questions end with a question mark.
Just use a copier in a public place. I have even paid for copies made in a bookstore once of a document I had.
If builders built buildings the way programmers wrote programs, then the first woodpecker would destroy civilization.
No, it doesn't allow it to be "traced back" because there is no registry of analog copiers. Color laser printers are special because you need no other detective work for finding the printer: the yellow dots are designed to make that identification trivial.
For other printing technologies (inkjet, black and white printers, etc.), you can only prove that a document came from a particular printer once you have "traced it back" via some other means.
Sigh - use a cheap consumer camera or phone. Photograph some secret documents. Pictures will be slightly unsharp, obliterating any small "dots" that the original printer put there. Text will still be readable.
Now, of course any digital camera add its own identifications but:
1. You can buy your cheapie camera/phone anonymously at a flea market, stopping the trace there. Toss it after use.
2. You can easily strip all EXIF from an image so the pixels are all that is left. In theory, there may be information hidden in pixels too, but the cameras tend to be Japanese/Korean not American. So less such nonsense.
3. Further obscurity by converting the image between formats several times, using different sw each time. Perhaps do some smoothing & sharpening to loose small details. Definitely convert to b&w. One of the steps might be "show it on screen", then do a screendump. The dump would remove all metainformation an image editor otherwise attempt to preserve.
If you are really paranoid, use an analog camera with b&w film that you develop yourself. Lots of photo artist/hobbyists still do that.
Names are typically very representative of culture, in particular parents culture. In this case "Reality Winner" pretty directly points to `hippy idealist nutcase' culture. Mohammed is typically muslim, whilst something like Eriksen in the US would typically be Scandinavian and of a higher cultural educational level (not having changed their name to a local one as most US poor or low culture immigrants do) etc. If you select or avoid people according to their surname then that will lead to unreasonable discrimination which is why recruiting places in civilised countries often avoid showing the surname on CVs during recruitment.
In other words, in the grandparents terminology, names are a "discriminatory item", or in longer form, a piece of information which could be used for immoral (and probably illegal) descrimination and which you shouldn't take into account when recruiting.