Dealing with Kindle for PC/Mac 1.19 and KFX in calibre

[JSWolf]

Originally Posted by jhowell

I was afraid of that.

I guess this answers the question of how serious Amazon is about maintaining the security of KFX DRM.

This is proof positive that KFX was invented to screw publishers who want their eBooks DRM free.

[Smoon]

I apologize if this is redundant. But what I am getting out of this is that today, Amazon changed the KFX to KFX-ZIP and DeDRM 6.8.0 is incapable of working on that?

[darryl]

Haven't tested yet but it does indeed answer the question. I wonder, however, how this change has been implemented. So far as I'm aware there has been no new version of K4PC, either Windows or Mac released. Yet it has stopped working immediately after the release of the new tools. Does this imply that the current release of K4PC has code which caters for Amazon changing the DRM. I wonder if this is the same with the Kindle firmware? I have a meeting shortly so don't have time to check now. But will do so as soon as I get the change. Interesting times.

[jhowell]

Originally Posted by Smoon

I apologize if this is redundant. But what I am getting out of this is that today, Amazon changed the KFX to KFX-ZIP and DeDRM 6.8.0 is incapable of working on that?

The KFX Input plugin locates all of the files that make up the book and packs them into a kfx-zip file. If DRM removal is unsuccessful that is what you get as the result of the import in your calibre library.

Still to soon to tell exactly what is happening, but my best guess is that Amazon's new KFX DRM is able to be changed on the fly somehow. That would indicate they have a stronger type of DRM than they have used previously.

[Smoon]

Originally Posted by jhowell

The KFX Input plugin locates all of the files that make up the book and packs them into a kfx-zip file. If DRM removal is unsuccessful that is what you get as the result of the import in your calibre library.

Still to soon to tell exactly what is happening, but my best guess is that Amazon's new KFX DRM is able to be changed on the fly somehow. That would indicate they have a stronger type of DRM than they have used previously.

Thanks! Interesting if they are able to do that without app updates.
Appreciate the explanation, learning as I go.

[lkmiller]

I'm guessing one thing that led to this was Pearson getting fed up with people buying etextbooks at the rental price, and then sharing them with 1000's of their "close friends."

[darryl]

Did a few quick tests before my meeting now in 7 minutes. I re-imported a book for K4PC and it decrypted succesfully. I deleted it from k4PC, re-downloaded it and it failed to decrypt. Adding a kfx from my Oasis decrypted fine. Will later try downloading a new book to my Kindle and trying that. Sounds like counter-measures are at least built in to K4PC. Don't yet know about firmware. With limited space, perhaps not. I should add I also tried deleting the default key from the plugin and getting it again. It did get the key successfully but still failed to decrypt.

Got to go.

[jhowell]

Originally Posted by darryl

Will later try downloading a new book to my Kindle and trying that. Sounds like counter-measures are at least built in to K4PC. Don't yet know about firmware. With limited space, perhaps not.

DeDRM for KFX worked yesterday on my Oasis running the latest 5.12.5 firmware. It no longer works today.

[darryl]

Originally Posted by jhowell

DeDRM for KFX worked yesterday on my Oasis running the latest 5.12.5 firmware. It no longer works today.

Interesting. Amazon is obviously very serious. I concur with Laura as you foreshadowed that it is probably motivated by our beloved educational publishers, or at least one of them. It seems Amazon wants at least one secure format.

What is most interesting is the fact that Amazon planned for this DRM scheme to be broken, and implemented at least one alternative in K4PC and firmware. It seems that it was able to implement the new scheme simply by changing the encryption at its end. Is it a new key or a new encryption algorithm or both?

[darryl]

One interesting thought. Anyone using earlier versions of K4PC which support kfx. Just wondering if this was planned from the start or whether the countermeasures were implemented later.

[ilovejedd]

Originally Posted by darryl

One interesting thought. Anyone using earlier versions of K4PC which support kfx. Just wondering if this was planned from the start or whether the countermeasures were implemented later.

I think that started on K4PC 1.25 or 26.

K4PC 1.19 - 1.24 continued working with the previous scripts even after the KFX DRM change.

On the e-ink side, the new KFX DRM was implemented on firmware 5.10.2.

[darryl]

Originally Posted by ilovejedd

I think that started on K4PC 1.25 or 26.

K4PC 1.19 - 1.24 continued working with the previous scripts even after the KFX DRM change.

On the e-ink side, the new KFX DRM was implemented on firmware 5.10.2.

Thanks. K4PC 1.24.3 works with latest tools to decrypt kfx books. K4PC 1.28.0 and latest Oasis firmware worked yesterday, but does not work now. Barring a sneaky update to 1.28 it appears that an alternate DRM scheme was included in that version and possibly some of the preceding versions after 1.24.3. It may be as simple as another key hidden in the software, an alternate decryption algorithm or both. As jhowell said, on the fly changes to DRM.

[pdurrant]

Wow. Now that's impressive.

[pdurrant]

Does the disabling KFX download still work on 1.28?

(I haven't updated from 1.17 yet, but I was considering a move to Mac OS 10.15 which would require 1.25 or later.)

[darryl]

It certainly is. I think we've benefited from Amazon not caring very much up until now. Hopefully Apprentice Sakuya will have a look at the matter. I'd be fascinated to see how they've actually done it.