Quote:
Originally Posted by wallcraft
I think of Amazon's setup as accounts and ebooks (files).
Your account lives on Amazon's servers, and it knows what ebook titles you own and what devices they are authorized on and which actually have copies of each ebook. If you ask for a new download, the server takes its master copy of that ebook and encrypts it for exactly the device/app+device you own (e.g. based on serial numbers, etcetera). So the files are locked to a single device, but your account allows (typically) 6 devices to have their own copies of each ebook.
This is why existing ebooks (files) still work when you switch accounts at Amazon. All new downloads will be from the new account and you can't get to the old account's ebooks (at Amazon). However, the ebook files from the old account still work because the device does not "know" about your account - it just knows how to decrypt ebooks when they are targeted uniquely to its serial number (or whatever the unique device id is).
An interesting end case is what happens if you have the same ebook in two accounts. Would the ebook file be identical if it was downloaded to the same device from the two accounts? From a DRM point of view, the original encryption (e.g. used on the Kindle 1) definitely was identical. I don't know if this is still the case with the latest Kindle 3 (and K4PC) encryption, but remember that a Kindle 3 can still read ebooks from old accounts. So it can't be very different.
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This is correct. The book is encrypted for the device when you download it to that device. That is why the drm removal tool needs the serial number or PID to work. It doesn't need to know anything about your amazon account.
The reason you can read the same book on multiple devices is not because the book is encrypted to your account, but your devices are registered to the same account. If you take the file that is on one device and do a byte comparison with the file on another device, I'm 99% sure they will be different. If you just copy the file on one kindle and put it on another, it will not be able to open it, even if they are both registered to your account. Again, because it is encrypted to the device. Now, if you sync your kindle, it will download another copy encrypted for that kindle and it will work.