CSS key cache collisions

[H}kan Hjort]

Thu Mar 27 2003, Gildas Bazin wrote:
> On Monday 24 March 2003 18:43, Michael Roitzsch wrote:
> > 
> > Attached is a patch which includes the serial number into the directory 
> > name. I don't know if this is guaranteed to be safe, but it works 
> > nicely here. The patch also fixes an issue when the key cache is used 
> > together with raw devices: The raw reading has to be enabled after 
> > extracting the disc title and serial, because otherwise the reads will 
> > fail due to the target buffers not being properly aligned in memory.
> > 
> > If James can confirm that this fixes the clashes, I would be glad if 
> > this could make it into cvs. Thanks.
> > 
> 
> Thanks for the patch, it has been applied to the cvs.
> 
Please, could we have some kind of interface for the keys/cache stuff.
I know that this might be agains the general idea with libdvdcss but
I don't think that you can really expect it to work without the user
knowing at least a bit about keys and various regions of the content.

I implemented a, in my opinion, robust DiscID function in libdvdread that
work not only on devices/images but also on mounted disc or file by file 
copies.  There where a pactch a little while back that tured of caching
for the 'non image' case because it caused collisions.  This is also the
normalcase of when the cache is most usefull as there is _no_ possibility
to get the keys from the drive. 
It's just unfortunat that there is a misconception among developers/users
that cause lots of people to use drives without ever setting the region.

So I'd want functions to get a key and to tell it to use a supplied
key.  It would also be good it one could get a special return code
(or mode of operation) where libdvdcss would wait to 'retrive' the key
until it either sees an encrypted block or it gets a read error.
This is so that one can avoid trying to get (and then crack) the keys
for any unencrypted titles (often video_ts.vob and / or vts_XX_0.vob, 
i.e the menu parts).

-- 
Håkan Hjort
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