MIT student Keith Winstein and MIT alum Marc Horowitz wrote and posted this very short Perl script that decrypts and plays DVD movies (though you’d need an extremely fast computer to watch a DVD movie in real time using Perl):
#!/usr/bin/perl -w
# 531-byte qrpff-fast, Keith Winstein and Marc Horowitz <[email protected]>
# 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){$a=29;$c=142;if((@a=unx"C*",$_)[20]&48){$h=5;
$_=unxb24,join"",@b=map{xB8,unxb8,chr($_^$a[--$h+84])}@ARGV;s/...$/1$&/;$d=
unxV,xb25,$_;$b=73;$e=256|(ord$b[4])<<9|ord$b[3];$d=$d>>8^($f=($t=255)&($d
>>12^$d>>4^$d^$d/8))<<17,$e=$e>>8^($t&($g=($q=$e>>14&7^$e)^$q*8^$q<<6))<<9
,$_=(map{$_%16or$t^=$c^=($m=(11,10,116,100,11,122,20,100)[$_/16%8])&110;$t
^=(72,@z=(64,72,$a^=12*($_%16-2?0:$m&17)),$b^=$_%64?12:0,@z)[$_%8]}(16..271))
[$_]^(($h>>=8)+=$f+(~$g&$t))for@a[128..$#a]}print+x"C*",@a}';s/x/pack+/g;eval
In doing so, have they committed a crime?
The authors of the program claim it doesn’t violate the DMCA in the same way that DeCSS does since it requires the user to provide the necessary title key in order to work. In a sense they are arguing that computer programs don’t decrypt DVDs, people decrypt DVDs.
I doubt this will fly legally, but this is yet another example of just how futile such copy protection schemes are.