ARC4

Category:	Cryptography
Author/Contact Info	Oromis92 mail ť nicolabbi@libero.it msn ť oromis92@email.it
Description:	this is a very simple code to encode a file or a string by ARC4. I don't use modules. I'm a relatively perl newbie... so the code isn't perfect
#!/usr/bin/perl -s # coded by Oromis92 # <nicolabbi@libero.it> $key = shift or die "usage: perl $0 [-d] <key> [infile [>> outfile]]\n +"; while (<>) { $plain .= $_; } chomp($plain); @key = split //,$key; @plain = split //,$plain; @key = map(ord, @key); @S = 0..255; foreach $i (0..255) { $K[$i]=$key[$i%($#key+1)]; } sub KSA { $j=0; for ($i=0;$i<255;$i++){ $j = ($j + $S[$i] + $K[$i])%256; $temp = $S[$i]; $S[$i] = $S[$j]; $S[$j] = $temp; } } sub PRGA { $i = 0; $j = 0; for ($count=0;$count<length($plain);$count++) { $i = ($i + 1)%256; $j = ($j + $S[$i])%256; $temp = $S[$i]; $S[$i] = $S[$j]; $S[$j] = $temp; $t = ($S[$i] + $S[$j])%256; if (!$d) { $output = sprintf('%X', ($S[$t] ^ ord($plain[$count]))); if (length($output) % 2 == 0) { $result .= $output; } else { $output .= "0" ; $result .= $output; $output = ""; } } else { if ($count2 < length($plain)) { $output = chr($S[$t] ^ (hex(substr($plain,($count2),2 +)))); $result .= $output; $output = ""; } } } print "$result\n"; } KSA; PRGA;

Comment on ARC4 Download Code
Re: ARC4 by wazoox (Prior) on Dec 01, 2008 at 11:34 UTC
Just a couple of comments : - Unless you know what you're doing, always add `use strict; use warnings;` at the top of your code. This will force you to declare variables and will save you a huge amount of problems. - Though "C style" loops are generally OK, people usually prefer "perlisms", for instance : `for my $i ( 0 .. 255 ) { # whatever }` [download]	[reply] [d/l] [select]
Re: ARC4 by andreas1234567 (Vicar) on Dec 01, 2008 at 12:49 UTC
You mean `ARC4` as in Alleged RC4? If yes, you know there are already modules for that, e.g. Crypt::RC4? -- No matter how great and destructive your problems may seem now, remember, you've probably only seen the tip of them. [1]	[reply] [d/l]