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[LinuxDVD] CSS Issues
Derek Fawcus derek@spider.com
Mon, 19 Jul 1999 17:58:35 +0100 

As I said,
I've been playing with the CSS code. [Updates on LiViD list], and have
found some interesting things.

I've been playin with the two DVD's that I currently own. One is the
'This is DVD' from 'What DVD', the other is the European release of
'Trainspotting'.

In dumping the Copyright structure and it looks as if 'This is DVD' is
encrypted and region 2 only, whereas 'Trainspotting' is unencrypted and
regions 1-6. Or at least one has a disk key and the other doesn't, I
don't know about the track key - I wasn't able to get anything sensible.

The region code seems to have bit's clear for the regions that the disk
can be played in. This contradicts the info in the copy of SFF-8090 I have
but agree's with something I remember reading on a web page.

I also found something odd about getting the ASF. It seems that one can
go throught the CSS sequence and the ASF is only set once one has retrieved
the disk yet. Thus with 'Trainspotting' I can't get the ASF set, but with
'This is DVD' I can. I guess I need a larger sample of DVDs.

Oops - I just noticed, the typescripts I saved don't show the errors
from the ide-cd driver. In them trying to read the disk key on
'Trainspotting' failed with the error saying there was no disk key
present and the error bytes (sk/asq ?) dumped also seemed to imply this
when reading SFF-8090.

One other thing I saw when browsing around web sites was a reference
that only upto 50% of the sectors in a title are encrypted? This seemed
a bit odd - how does one tell which are which.

Also Title Keys. How do they fit in with the above. From SFF-8090 I
guess I have to supply the starting LBA for a given title, and I'll then
get back the Title key obfuscated with the Bus Key. However don't I need
to parse the .IFO files in order to get the LBA for the Title?

DF
-- 
Derek Fawcus derek@spider.com
Spider Software Ltd. +44 (0) 131 475 7034

[LinuxDVD] CSS Issues
Paul Volcko pvolcko@concentric.net
Mon, 19 Jul 1999 13:33:04 -0400 

> The region code seems to have bit's clear for the regions that the disk
> can be played in. This contradicts the info in the copy of SFF-8090 I have
> but agree's with something I remember reading on a web page.

This is correct, 0 bits are playable regions, 1 bits are blocked 
regions. If bit 8 is 0 then it is playable in all regions.

> One other thing I saw when browsing around web sites was a reference
> that only upto 50% of the sectors in a title are encrypted? This seemed
> a bit odd - how does one tell which are which.

I've never seen anything like that before in my readings of the dvd 
specs or any other sources. It would seem to be somewhat 
counter intuitive. Why go to the trouble of protecting anything if 
you're going to leave some of it in the clear? Defeats the purpose I 
would think. No to mention I've done entire .vob file dumps before 
and gotten nothing but bad reads, well over 50% of the disc space 
yielded this.

> Also Title Keys. How do they fit in with the above. From SFF-8090 I
> guess I have to supply the starting LBA for a given title, and I'll then
> get back the Title key obfuscated with the Bus Key. However don't I need
> to parse the .IFO files in order to get the LBA for the Title?

The video_ts.ifo file contains all the information needed for finding 
titles and their start addresses in the Title Search Pointer Table 
(basic information on this and other sections of the IFO files canbe 
found at http://linuxtv.org/dvd/fs.html)


What is SFF-8090?

Paul Volcko
LSDVD Project

[LinuxDVD] CSS Issues
Derek Fawcus derek@spider.com
Mon, 19 Jul 1999 20:51:25 +0100 

On Mon, Jul 19, 1999 at 01:33:04PM -0400, Paul Volcko wrote:
> 
> > One other thing I saw when browsing around web sites was a reference
> > that only upto 50% of the sectors in a title are encrypted? This seemed
> > a bit odd - how does one tell which are which.
> 
> I've never seen anything like that before in my readings of the dvd 
> specs or any other sources. It would seem to be somewhat 
> counter intuitive. Why go to the trouble of protecting anything if 
> you're going to leave some of it in the clear? Defeats the purpose I 
> would think. No to mention I've done entire .vob file dumps before 
> and gotten nothing but bad reads, well over 50% of the disc space 
> yielded this.

Makes sense.

> > Also Title Keys. How do they fit in with the above. From SFF-8090 I
> > guess I have to supply the starting LBA for a given title, and I'll then
> > get back the Title key obfuscated with the Bus Key. However don't I need
> > to parse the .IFO files in order to get the LBA for the Title?
> 
> The video_ts.ifo file contains all the information needed for finding 
> titles and their start addresses in the Title Search Pointer Table 
> (basic information on this and other sections of the IFO files canbe 
> found at http://linuxtv.org/dvd/fs.html)

I didn't explain myself too well in the above. What I wanted to know
was the question you asked in the last paragraph of your later mail. i.e.
why have disk & title keys?

> What is SFF-8090?

The spec for ATAPI DVD-ROM/DVD-RAM/CD-ROM drives. It describes the format
of the packet commands used in the CSS negotiation.

DF
-- 
Derek Fawcus derek@spider.com
Spider Software Ltd. +44 (0) 131 475 7034

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