[MPlayer-users] Re: how does mplayer circumvent region protected (RPC-2) DVD drives?

[Robert R. Wal]

On 02.10.18 Tobias Diedrich pressed the following keys:

> Louis-David Mitterrand wrote:
> 
> > On my new laptop the DVD drive is RPC-2 (region protected). However it
> > after swapping region 1 and 2 disks way beyond the 5-change limit, DVDs
> > still work fine under Linux and mplayer. Under WinXP the drive's
> > internal region change counter is still the same.
> > 
> > How does mplayer circumvent this restriction? Does it read the DVD files
> > in DVD-Rom mode instead of DVD player mode?
> 
> mplayer (or libdvdread, for that matter) does not circumvent this
> restriction at all.

You're wrong. mplayer does circumvent this protection. Some time ago
Arpi was so kind that he explained what actually happens in mpdvdkit
that it can read disks from other regions in RPC2 drives.

Thing is that there are several phases of authentication. If I remember
correctly:

1. Player authenticates with player key, gets disc key.
2. Player unlocks ``hidden sectors'' with disc key. Hidden sectors
contain title keys for each title on DVD, and sometimes several sectors
of the VOB-s themselves.
3. Player requests title key.
4. Read, decrypt using title key and play.

For the reason beyond my knowledge region checks in RPC2 drives are
performed only in stage 3. mpdvdkit avoids them by not requesting the
key at all, it cracks the key using ,,known plaintext attack'' on VOB
contents.

Robert

PS. Maybe it should go to TFM after all...

PPS. I suspect that the reason why those checks are performed in stage
3 only is that DVD standard may allow for DVD discs containing several
titles with different region restrictions.

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