'qrpff', written by
Keith Winstein and
Marc Horowitz for a
MIT seminar on
decrypting DVD, is a 7 line piece of
perl code that decrypts
DVD technology. Previous
programs that decrypted
DVD data (such as
DeCSS) were declared
illegal and were removed from the
2600 website.
Winstein, a 19 year old MIT computer science major, said of his code, "I think there's some value in demonstrating how simple these things really are and how preposterous it is to try to restrict their distribution."
Because the code does not include a 5 bit title key (not really sure why it's important, to be honest) many claim that it does not violate the Digital Millennium Copyright Act, which was used against DeCSS. I find it very odd (and strangely gratifying) that something so valuable to the pockets of major movie industries can be beat with only seven lines of Perl. All hail the mighty Camel.
It's quite a bit over my head, but maybe some of you can make sense of it. By the way, in my opinion this is a very Good Thing. And now, without further ado, here's the code.
$_='while(read+STDIN,$_,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;$t^=(72,@z=(64,72,$a^=12*($_%16
-2?0:$m&17)),$b^=$_%64?12:0,@z)[$_%8]}(16..271);if((@a=unx"C*",$_)[ 20]&48){$h
=5;$_=unxb24,join"",@b=map{xB8,unxb8,chr($_^$a[--$h+84 ])}@ARGV;s/...$/1$&/;$
d=unxV,xb25,$_;$e=256|(ord$b4)<<9|ord$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@a[ 128..$#a]}print+x"C*",@a}';s/x/pack+/g;eval
Typical usage is just: cat /mnt/dvd/VOB_FILE_NAME | qrpff 153 2 8 105 225 | extract_mpeg2 | mpeg2dec -
Information from slashdot.com and wired.com were used in the creation of this node.