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?
You can mess with the levels to see any hidden watermarks
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”
But what transformations are they stable to?
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.