How many watermarks (embedded personal information) exist on the Kindle?

[GranSenser]

I know that there is meta name="Watermark_(hex)" in the opf file in the azw&epub file.

But I do not know if there are any other watermarks.

Is "uid" or "uuid" tag in .opf a watermark?

In the customization options of dedrm there is an option "remove watermark", to what extent does this work?

[Quoth]

Unless you are pirating copies it's irrelevant.

I care about privacy, but in this case it doesn't matter.

[JSWolf]

I believe it's just the watermark in the header for Mobi or KF8. It gets stripped when you run the latest DeDRM, but it will not get stripped if the eBook has no DRM as DeDRM won't do anything with the eBook.

[GranSenser]

Originally Posted by Quoth

Unless you are pirating copies it's irrelevant.

I care about privacy, but in this case it doesn't matter.

I think users have a right to know where their personal information is stored in the file.

Originally Posted by JSWolf

I believe it's just the watermark in the header for Mobi or KF8. It gets stripped when you run the latest DeDRM, but it will not get stripped if the eBook has no DRM as DeDRM won't do anything with the eBook.

thank you for Answer.
I see, this option only works when DRM is present.
Is the header watermark a set with DRM?

[gbm]

uuid

When generated according to the standard methods, UUIDs are, for practical purposes, unique. Their uniqueness does not depend on a central registration authority or coordination between the parties generating them, unlike most other numbering schemes. While the probability that a UUID will be duplicated is not zero, it is close enough to zero to be negligible.[2][3]

So if generated by Amazon it could be used as a watermark.

bernie

Originally Posted by GranSenser

I know that there is meta name="Watermark_(hex)" in the opf file in the azw&epub file.

But I do not know if there are any other watermarks.

Is "uid" or "uuid" tag in .opf a watermark?

In the customization options of dedrm there is an option "remove watermark", to what extent does this work?

[jhowell]

Originally Posted by GranSenser

I think users have a right to know where their personal information is stored in the file.

I wouldn't worry about the watermark leaking your personal information. It is encrypted. And while any encryption can eventually be broken, no one other than Amazon has any real incentive to decode watermarks.

Originally Posted by GranSenser

Is the header watermark a set with DRM?

No. The watermark is part on the metadata of the book. It is stored in the EXTH header along with the title, author, and other metadata. It is present even if a book does not have DRM. Each time a book is downloaded or delivered it is given a new unique watermark.

DRM data is stored separately in a 48 byte DRM voucher.

[GranSenser]

Originally Posted by gbm

So if generated by Amazon it could be used as a watermark.

bernie

Originally Posted by jhowell

I wouldn't worry about the watermark leaking your personal information. It is encrypted. And while any encryption can eventually be broken, no one other than Amazon has any real incentive to decode watermarks.


No. The watermark is part on the metadata of the book. It is stored in the EXTH header along with the title, author, and other metadata. It is present even if a book does not have DRM. Each time a book is downloaded or delivered it is given a new unique watermark.

DRM data is stored separately in a 48 byte DRM voucher.

thank you for answer.

Is that 48 bytes identical to the atv tag in this post?

https://www.mobileread.com/forums/sh....php?p=1957715

[jhowell]

Originally Posted by GranSenser

thank you for answer.

Is that 48 bytes identical to the atv tag in this post?

https://www.mobileread.com/forums/sh....php?p=1957715

No. That post has a partial description of the watermark format.

The watermark is encrypted but it is possible to infer what sort of things it encodes. By comparing many watermarks it is possible to find correlations showing that one part is associated with the customer's account and another part with the particular book.

The DRM voucher is binary data that holds the key needed to decrypt contents of the book which is itself encrypted. It is stored in a separate part of the first record of the MOBI file as binary data.

[GranSenser]

Originally Posted by jhowell

No. That post has a partial description of the watermark format.

The watermark is encrypted but it is possible to infer what sort of things it encodes. By comparing many watermarks it is possible to find correlations showing that one part is associated with the customer's account and another part with the particular book.

The DRM voucher is binary data that holds the key needed to decrypt contents of the book which is itself encrypted. It is stored in a separate part of the first record of the MOBI file as binary data.

Thank you for your solution.
Then the voucher is removed by DeDRM, and only when the voucher is present, the watermark in the EXTH header is also removed.
I understood most of what you said.

And as to the thread title.
I see the watermark is just the .opf tag and the EXTH header.
So the kindle watermark is simpler than I thought.