I know Calibre can remove DRM, but it seems that Calibre does not remove things like watermarks, references to the buyer by name, etc. Now maybe I can try to find those manually, but that is an error prone process. Plus, what if they embed a unique digital signature that ties back to me? I understand that this is a very uncommon practice, but I do not want to find myself in a bad place.

I suppose the only way to remove a digital signature of any sort is to buy two of the same e-book by different people, diff them, and remove anything that differentiates them.

Is there any tool that does this or automates the process? am I being too paranoid, and this is not a real threat?

  • matcha_addict@lemy.lolOPEnglish
    28·
    10 months ago

    Thanks for your advice. I am a programmer by craft so I can definitely do that. I think the only issue may be books with any important content that is not text, i.e. graphics and images (and unfortunately, many of the books I am interested in have that). If I understood what you said correctly.

        • iopq@lemmy.worldEnglish
          31·
          10 months ago

          You can mess with the levels to see any hidden watermarks

          • FierySpectre@lemmy.worldEnglish
            8·
            10 months ago

            There are so many ways to encode information into an image without changing its look that I doubt you’ll find most of them by “changing levels”

            • conciselyverbose@sh.itjust.worksEnglish
              3·
              10 months ago

              I’d personally be a lot more likely to blur and add random noise, then use lossy compression if I wanted to mitigate steganography, but even then, they don’t need to encode a lot of information and they have a base image and secrets to compare to. It’s entirely possible for them to have chosen something reasonably robust through random edits like that.

        • Lemongrab@lemmy.oneEnglish
          31·
          10 months ago

          Theoretically, yes. Handling of images programmatically could allow for some simple lossy compression which would help.

    • Kindness@lemmy.mlEnglish
      2·
      10 months ago

      gImageReader or ocrmypdf will get you the pdf text, but after the text will need fiddling with and cleaning. Use LibreOffice, languagetool, write-good, etc to make finding the oddballs easy.

      pdftk is what you want for editing pdf metadata.

      Gimp is what you’ll need for editing images, Looking for watermarks, smoothing edges, lowering quality, introducing random noise, etc.

      exiftool is what you’ll need for image metadata. Or take a screenshot, add a bit of noise or de-noise, and add back to the new pdf.

      Scrivener or LibreOffice if you want to polish/republish, though that’s a ton of work.