[MPlayer-users] [OT] AC3 vs. DTS

[Giacomo Comes]

On Mon, Aug 01, 2005 at 05:14:33PM -0400, Rich Felker wrote:
> On Mon, Aug 01, 2005 at 03:58:11PM -0400, Giacomo Comes wrote:
> > On Mon, Aug 01, 2005 at 02:12:36PM -0400, Rich Felker wrote:
> > > On Mon, Aug 01, 2005 at 11:43:00AM -0400, Giacomo Comes wrote:
> > > > > > For the future I'm still waiting for the next big thing, since I'm not 
> > > > > > that happy with the heavily protected new HD formats. I still want to be 
> > > > > 
> > > > > Heavily protected? Any cryptography where the attacker has the key is
> > > > > not heavily protected, it's just basic obscuring/obfuscation and will
> > > > > be cracked in no time, just like CSS.
> > > > 
> > > > That's completly false. You are talking only about weak encription 
> > > > algorithms like CSS. CSS was a "secret" algorithm. Once people understood
> > > > how it was working (knowing some keys) they found how weak it was 
> > > > and how to guess the keys analizing the encrypted data (what libdvdcss does).
> > > 
> > > You fucking didn't read what I wrote. If you can play the movie, YOU
> > > HAVE THE KEY. DRM/"content protection" is always obfuscation, not
> > > cryptography.
> > 
> > It seems that I make you angry, because you start insulting people.
> 
> Not insulting, just yelling. And it's because you called my statements
> false when you apparently have no clue about crypto.

I was thinking the same about you :-)

> > Anyway I read what you wrote. I just want to remember you that CSS
> > was not cracked in no time. It took some years after the introduction of
> > the DVD technology, and the crackers succeed because they found a key not 
> > obfuscated in a software player.
> 
> DVD was cracked way before DVD drives were common in computers. Before
> that, there was really very little motivation:
> 
> 1. Compression software and bandwidth for distributing movies over the
>    net were severely lacking at the time, so the warez scene had
>    little motive. Most people were sharing analog-captured .asf and
>    .rm files if anything at all.. :)
> 
> 2. Since few computers had DVD drives, no one cared if they could play
>    their DVDs on their non-windows computer.
> 
> The digital media scene on the net is much more developed now, and I'm
> confident that competent people will attack whatever new crap they
> throw at us quickly and liberate it as well.
> 
> > In your statement you say that knowing a key "will make the cryptography
> > be cracked in no time"
> > That's only valid if the encryption algorithm is weak.
> 
> No, this statement is blatently false. Assuming you know the key (or
> have it somewhere and just haven't found it), the only factors making
> it difficult to crack the 'protection' are the level of obfuscation of
> the key and the level of obfuscation of the encryption (i.e. using an
> encryption method that's not well-known). Both of these are matters of
> security through obscurity. The weakness or strength of the encryption
> itself is always irrelevant when the only security comes from
> obscurity.

Looks like you were thinking about circumventing a protection,
but you were talking about breaking cryptography.
Circumventing a 'protection' is one thing, it can be easy.
Breaking a cryptograph algorithm is another thing.
libdvdcss does not circumvent CSS, it breaks the weak algorithm.

Giacomo