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How do we find out if our files (audio, images, pdf, videos) are digital watermarked by the distributors?

user160411
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  • I think that un-watermarking is the solution to be sure they are not watermarked. Editing the file and saving it should be enough for the watermark to be gone in case the watermark is some hidden info in the file and is not a visible or audible watermark. – YoMismo Oct 04 '17 at 07:08
  • Look into: Steganalysis – downwardCorgi Oct 04 '17 at 14:32

1 Answers1

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TL;DR: It may not necessarily be possible.

Long explanation: Most digital watermarks are visible, as they're not intended to be hidden. For example, an image watermark may be overlaid on top of the original image. Another common watermark is as a metadata for file formats that supports metadata attachment.

But it's also possible to place a hidden, in-band watermark that is statistically indistinguishable from regular image, but can be checked by someone who knows how. For example, the distributor may alter the least significant bit of each pixel channels in an image so they form a unique signature that identifies the distributor or the original licensee.

Unless you have the original, unaltered version of the image, it may be impossible to detect the watermark made in such way. It may also be possible to detect the watermark by comparing the image against other licensed copy of the image.

Similar techniques exist for audio and video files, and some document format.

Lie Ryan
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