[WEB4LIB] RE: Gray Hats Re: Re: Jack Valenti: Copyright and
Tony Barry
me at Tony-Barry.emu.id.au
Tue Mar 20 21:21:58 EST 2001
At 2:53 PM -0800 20/3/01, Chris Deweese wrote:
>Again we see hacking being classified in a "dark" manner. As matt
>said, hacking is about the method and not the context. Might I
>suggest this story:
>Seven-Line Perl code beats DVD Crypto
>http://www.theregister.co.uk/content/4/17444.html
>A seven-line program written in perl script beats the MPAA's DVD
>encryption scheme. The program was written by a former MIT student
>and a currnet undergrad. A pure example of hacking being about the
>method.
>These guys didnt write this program to copy dvd's. They wrote it to
>prove how weak the system currently used is. deCSS the original
>program to decrypt dvds was written by a 15 year old kid.
>I see no wrong doing in this. But the MPAA has been in an uproar
>about it. Why? Because it shows how little money they really
>invested in coming up with a copy protection system. More money is
>probably invested in child safety caps for medicine.(thats a guess
>not a fact)
The code is -
#!/usr/bin/perl -w
# 531-byte qrpff-fast, Keith Winstein and Marc Horowitz <sipb-iap-dvd at mit.edu>
# MPEG 2 PS VOB file on stdin -> descrambled output on stdout
# arguments: title key bytes in least to most-significant order
$_='while(read+STDIN,$_,2048){$a=29;$b=73;$c=142;$t=255;@t=map{$_%16or$t^=$c^=(
$m=(11,10,116,100,11,122,20,100)[$_/16%8])&110;$t^=(72, at z=(64,72,$a^=12*($_%16
-2?0:$m&17)),$b^=$_%64?12:0, at z)[$_%8]}(16..271);if((@a=unx"C*",$_)[20]&48){$h
=5;$_=unxb24,join"", at b=map{xB8,unxb8,chr($_^$a[--$h+84])}@ARGV;s/...$/1$&/;$
d=unxV,xb25,$_;$e=256|(ord$b[4])<<9|ord$b[3];$d=$d>>8^($f=$t&($d>>12^$d>>4^
$d^$d/8))<<17,$e=$e>>8^($t&($g=($q=$e>>14&7^$e)^$q*8^$q<<6))<<9,$_=$t[$_]^
(($h>>=8)+=$f+(~$g&$t))for at a[128..$#a]}print+x"C*", at a}';s/x/pack+/g;eval
It has also been written as an ever shorter c++ program and(using a
bit of a trick) as a prime number.
Also the web4lib archives may be in breach of the copyright
legislation for publishing this ;^)
Tony
--
phone +61 2 6241 7659
mailto:me at Tony-Barry.emu.id.au
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