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haertig · 05-04-2019, 10:47 PM

I just checked a book that I bought from Amazon about 3 months ago. There is no trace of a human-readable version of my credentials in either the DRM'ed azw3 file or in the Calibre DRM-stripped version of the file. Note: Both my Amazon credentials and my email address contain a unique text string that I searched for, so you'd expect that might be what shows up, if an identifier was there.

I'm not saying that an identifier is not there - it could be stored in some non-human-readable form (encrypted) - I'm just saying that it is not there in plain ASCII text form.

Test that was run from Linux:

"strings filename.azw3 | grep -i unique_string" (where "unique_string" is a string of letters found in my amazon credentials and also in my email address on file with Amazon)

I searched "filename.azw3" as it existed straight from Amazon, before import into Calibre, and also after Calibre had de-DRM'ed it and stored it in the Calibre file structure.

So if Amazon is indeed watermarking book purchases, they're being sneaky in the way they do it. Encrypting or in some other way scrambling the watermark. Or they could be using some other identifier - maybe some internal database row_id that uniquely identifies me in a way that only Amazon would know.

There is this one slightly suspicious looking text section found in the ebook azw3 file which could be an encrypted watermark:

Code:

Ariel
EBOK
atv:kin:2:ihS5FEWN2tLW9uSBqK26KD3Lhf8ZAE/kZQboZ9lrS3ZEIkMD0HOtwIFE/SNthee6rvhziZWx4TSxfWCftHj8+PUHAEqBMY5cdYM7wwBzlTYwNNTiydy1UEBKfQNbvqkGaK8yRdxjAqRDiUGhQ7Vx11kvhp+jw+K092Etcs21igA=:/Ty5lDTBtCXV78x859TIchV4ovw=
Ariel

Note that the book I bought was "Ariel", by Steven R. Boyett - that text shows up both before and after the suspicious "atv:kin:2" string. I didn't find anything else that aroused my suspicion as a watermark in the ebook. I guess if one were paranoid, I would try manually editing out the atv:kin:2 line and then test to see if the ebook still functions normally. The potential exists that you could really bork up an ebook by manually removing lines of text that you don't understand the structure of, so beware.

05-04-2019, 10:47 PM	#7
haertig Wizard Posts: 1,929 Karma: 34302982 Join Date: Sep 2017 Device: PW3, Galaxy Tab A9+, Moto G7	I just checked a book that I bought from Amazon about 3 months ago. There is no trace of a human-readable version of my credentials in either the DRM'ed azw3 file or in the Calibre DRM-stripped version of the file. Note: Both my Amazon credentials and my email address contain a unique text string that I searched for, so you'd expect that might be what shows up, if an identifier was there. I'm not saying that an identifier is not there - it could be stored in some non-human-readable form (encrypted) - I'm just saying that it is not there in plain ASCII text form. Test that was run from Linux: "strings filename.azw3 \| grep -i unique_string" (where "unique_string" is a string of letters found in my amazon credentials and also in my email address on file with Amazon) I searched "filename.azw3" as it existed straight from Amazon, before import into Calibre, and also after Calibre had de-DRM'ed it and stored it in the Calibre file structure. So if Amazon is indeed watermarking book purchases, they're being sneaky in the way they do it. Encrypting or in some other way scrambling the watermark. Or they could be using some other identifier - maybe some internal database row_id that uniquely identifies me in a way that only Amazon would know. There is this one slightly suspicious looking text section found in the ebook azw3 file which could be an encrypted watermark: Code: Ariel EBOK atv:kin:2:ihS5FEWN2tLW9uSBqK26KD3Lhf8ZAE/kZQboZ9lrS3ZEIkMD0HOtwIFE/SNthee6rvhziZWx4TSxfWCftHj8+PUHAEqBMY5cdYM7wwBzlTYwNNTiydy1UEBKfQNbvqkGaK8yRdxjAqRDiUGhQ7Vx11kvhp+jw+K092Etcs21igA=:/Ty5lDTBtCXV78x859TIchV4ovw= Ariel Note that the book I bought was "Ariel", by Steven R. Boyett - that text shows up both before and after the suspicious "atv:kin:2" string. I didn't find anything else that aroused my suspicion as a watermark in the ebook. I guess if one were paranoid, I would try manually editing out the atv:kin:2 line and then test to see if the ebook still functions normally. The potential exists that you could really bork up an ebook by manually removing lines of text that you don't understand the structure of, so beware. Last edited by haertig; 05-04-2019 at 10:49 PM.