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

Rich Felker dalias at aerifal.cx
Mon Aug 1 23:14:33 CEST 2005

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.

> 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


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