>>16You can know for certain if you compromise the canary trap department. But even if you don't you can run the original through enough transformations where recovery of the original watermark would take more resources than would be worth the effort. If you are lucky, all traces of the watermark are obliterated. If some remain, then you would hope that the distortion modified the watermark to the point where it can't be distinguished from it's other versions. Depending on the transformation, this can be high probability. The transformation would need to be suited for the watermark. In the worst case, the watermark is the content of the document itself, and the different versions given to the privileged members are all completely different. In this case the only safe transformation is one that reduces the text to pure noise and destroys all the content. Ergo, you're wrong. If I xor every bit of the document with a random bit array you'll never know what it was originally and the leaker is safe. Unfortunately the content of the document is also destroyed.