Samy Kamkar wrote:
>
> Hi everyone!
Hello,
> Uri just pointed me out to this list today and I'm glad he did :)
>
> Well, I'd like to know if any of you are able to shorten this, I spent a
> few minutes last night and this morning shortening it to 182 bytes and
> I'm not sure what else can be done to it but I'm sure many of you here
> will be able to shorten it a great deal
>
> It's RC4, so far in 182 bytes, accepts a hex key (e.g., a0b1c2) in
> $ARGV[0] and reads input from <>:
> sub
> f{@s[$x,$y]=@s[$y,$x]}@k=map{hex}pop=~/../g;$y=($y+$k[$_%@k]+$s[$x=$_])%256,f
> for@t=@s=0..255;$x=$y=0;$x++,$y+=$s[$x%=256]%256,f,print
> chr($s[($s[$x]+$s[$y])%256]^ord)for<>=~/./g
>
> so: perl -e 'print"blah"' | perl -e '...' a0b1c2
> would print out the ASCII value of \xe8\x9c\xc0\xcb
It should print out 0xe8 0x9c 0xcf 0x92 (which the C version does.)
According to AC[1] the correct algorithm is:
i = (i + 1) mod 256
j = (j + Si) mod 256
swap Si and Sj
t = (Si + Sj) mod 256
K = St
So change:
$x++, $y += $s[ $x %= 256 ] % 256,
To:
$y = ($y + $s[ $x = ($x + 1) % 256 ]) % 256,
John
[1] Applied Cryptography, Bruce Schneier
--
use Perl;
program
fulfillment
