3 ms·

Does anyone know if ebooks are watermarked in a similar way?

by sien 6y ago

worker767424 6y ago
Not sure about ebooks, but I assume every workplace email sent to all does this to catch leaks.
Polylactic_acid 6y ago
They almost certainly are for some sources. And probably with your unique user id to work out who leaked the copy on to torrent sites. The way to check this is pretty easy though, get 2 users to bit for bit compare their books to work out if they are identical.
- young_unixer 6y ago
  Open the book in Evince, Print to PDF. Bam, your book is now anonymous.
  - probably_wrong 6y ago
    I am not following your line of reasoning correctly. The watermarking is done using characters that look different from each other. Printing the book will not change those characters, and therefore it is still possible to extract the original information. Harder, but not impossible. For this information to be lost, Evince would have to print the book in a crappy font that uses a single symbol for both. Which is possible, but I think it's not what you were going for.
    - young_unixer 6y ago
      The hash won't be the same, which is what matters the most. They won't have people manually reviewing the punctuation to catch infringement, and it's highly probable that Evince printing to PDF will mess the whole internal structure, so it's hard to automate it.
      - Polylactic_acid 6y ago
        If you just print it then that defeats the point. They don't care about individual copies, they want to find who is stripping DRM and posting books on torrent trackers.
  - ceejayoz 6y ago
    How likely are you to notice if your resulting PDF had a specific unique pattern of zero-width spaces embedded with it? Or if a few curly quotes aren't curly? Let alone scenarios like the cover JPEG having stenographic info in it...
rwmj 6y ago
Not ebooks, but interesting technique used to find who is leaking your sensitive documents: https://en.wikipedia.org/wiki/Canary_trap https://en.wikipedia.org/wiki/Canary_trap
efreak 6y ago
Absolutely. It usually tends to be either more visible, or less visible though - some pdf files have a literal watermark on the pages, while other formats like epub contain a guid or other watermark content in the source (epub is zipped xhtml) https://gizmodo.com/harpercollins-is-now-using-digital-watermarks-to-stop-e-1635220938 https://gizmodo.com/harpercollins-is-now-using-digital-water... https://goodereader.com/blog/e-book-news/everything-you-need-to-know-about-social-drm-for-ebooks https://goodereader.com/blog/e-book-news/everything-you-need... Amusingly, I believe if you use calibre's ebook conversion to replace stylesheets and add toc, it may also actually remove those markers that have no actual content and only exist to provide a unique ID.

Does anyone know if ebooks are watermarked in a similar way?

by sien 6y ago

Does anyone know if ebooks are watermarked in a similar way?

worker767424 6y ago

Not sure about ebooks, but I assume every workplace email sent to all does this to catch leaks.

Polylactic_acid 6y ago

They almost certainly are for some sources. And probably with your unique user id to work out who leaked the copy on to torrent sites. The way to check this is pretty easy though, get 2 users to bit for bit compare their books to work out if they are identical.

young_unixer 6y ago
Open the book in Evince, Print to PDF. Bam, your book is now anonymous.
- probably_wrong 6y ago
  I am not following your line of reasoning correctly. The watermarking is done using characters that look different from each other. Printing the book will not change those characters, and therefore it is still possible to extract the original information. Harder, but not impossible. For this information to be lost, Evince would have to print the book in a crappy font that uses a single symbol for both. Which is possible, but I think it's not what you were going for.
  - young_unixer 6y ago
    The hash won't be the same, which is what matters the most. They won't have people manually reviewing the punctuation to catch infringement, and it's highly probable that Evince printing to PDF will mess the whole internal structure, so it's hard to automate it.
    - Polylactic_acid 6y ago
      If you just print it then that defeats the point. They don't care about individual copies, they want to find who is stripping DRM and posting books on torrent trackers.
- ceejayoz 6y ago
  How likely are you to notice if your resulting PDF had a specific unique pattern of zero-width spaces embedded with it? Or if a few curly quotes aren't curly? Let alone scenarios like the cover JPEG having stenographic info in it...

rwmj 6y ago

Not ebooks, but interesting technique used to find who is leaking your sensitive documents: https://en.wikipedia.org/wiki/Canary_trap https://en.wikipedia.org/wiki/Canary_trap

efreak 6y ago

Absolutely. It usually tends to be either more visible, or less visible though - some pdf files have a literal watermark on the pages, while other formats like epub contain a guid or other watermark content in the source (epub is zipped xhtml) https://gizmodo.com/harpercollins-is-now-using-digital-watermarks-to-stop-e-1635220938 https://gizmodo.com/harpercollins-is-now-using-digital-water... https://goodereader.com/blog/e-book-news/everything-you-need-to-know-about-social-drm-for-ebooks https://goodereader.com/blog/e-book-news/everything-you-need... Amusingly, I believe if you use calibre's ebook conversion to replace stylesheets and add toc, it may also actually remove those markers that have no actual content and only exist to provide a unique ID.