• sandbox@lemmy.world
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    5 months ago

    it’s possible using steganographic techniques to embed digital watermarks which would not be stripped by simply printing to pdf.

      • Syn_Attck@lemmy.today
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        5 months ago

        You should spread that idea around more, it’s pretty ingenious. I’d add first converting to B&W if possible.

    • Syn_Attck@lemmy.today
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      5 months ago

      This is a great point. Image watermarking steganography is nearly impossible to defeat unless you can obtain multiple copies of the ‘same’ file from multiple users to look for differences. It could be a change of a single 5-15 pixels from one rgb code off.

      rgb(255, 251, 0)

      to

      rgb(255, 252, 0)

      Which would be imperceptable to the human eye. Depending on the number of users it may need to change more or less pixels.

      There is a ton of work in this field and its very interesting, for anyone considering majoring in computer science / information security.

      Another ‘neat’ technology everyone should know about is machine identification codes, or, the tiny secret tracking dots that color printers print on every page to identify the specific make, model, and serial number (I think?) of the printer the page was printed from. I don’t believe B&W printers have tracking dots, which were originally used to track creators of counterfeit currency. EFF has a page of color printers which do not include tracking dots on printed pages. This includes color LaserJets along with InkJets, although I would not be surprised if there was a similar tracking feature in place now or in the future “for safety and privacy reasons,” but none that I am aware of.