Re: [libdvdcss-devel] bit perfect copies of CSS DVDs

Hello,

On 30 Jun, Christoph Anton Mitterer wrote :
> So is there actually some drive level encryption that happens before
> the block layer, and libdvdcss initialises the drive with the correct
> keys?
> Right?

Right. CSS is both at the file level and at the disk level. You cannot
dd directly and have something working.
Therefore, when doing copies, you will always remove some part of CSS
encryption.

> 2) I further noticed that even when first playing the DVD and then
> creating an image with e.g. dd (which works fine then), the contents of
> the UDF fs within that image differ binary from what e.g. tools like
> dvdbackup would dump me to disk (i.e. VOBs, IFOs, etc. but without the
> UDF fs around).
> 
> So it seems that in addition to the drive level encryption/protection,
> which is defeated in (1), there's still another file level encryption?
> Right?

Well, yes, but I don't know how is that related to your 2).
Are you referring about ARCCOS system?

> 3) Interestingly, when I create two images of the same DVD (without
> ejecting it in the meantime or clearing up ~/.dvdcss/) than these
> images still always differ in 10 bytes or so, always at the same
> location.
> Any idea why?

No. That seems like a bug.

With my kindest regards,

-- 
Jean-Baptiste Kempf
http://www.jbkempf.com/ - +33 672 704 734
Sent from my Electronic Device
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