#!/usr/bin/env perl
use strict; #use warnings;
use List::Util qw(first);

my $key="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";
$key=pack('H*',$key);

my @sbase;
for my $i (0..255){$sbase[$i]=chr($i)};

my @sbox=sbox_gen(@sbase);

if ( $ARGV[2] eq "fwd" ) {
	fwd();
} elsif ( $ARGV[2] eq "rev" ) {
	rev();
}

sub fwd {
my ($n,$infile,$buf,$data,$outfile,$tmp);
open($infile,"<",$ARGV[0]) or die $!; binmode($infile);
open($outfile,">",$ARGV[1]) or die $!; binmode($outfile);
while (($n=sysread $infile,$buf,256)!=0){
	for my $i (0..255) {
		$tmp=ord(substr($buf,$i,1));
		$data.=$sbox[$tmp];
	}
	print $outfile $data;$data="";
}
close($outfile);
close($infile);
}

sub rev {
my ($n,$infile,$buf,$data,$outfile,$tmp);
open($infile,"<",$ARGV[0]) or die $!; binmode($infile);
open($outfile,">",$ARGV[1]) or die $!; binmode($outfile);
while (($n=sysread $infile,$buf,256)!=0){
	for my $i (0..255) {
		$tmp=substr($buf,$i,1);
		#my $index=first { $sbox[$_] eq $tmp } 0 .. $#sbox;
		#$data.=chr($index);
		for my $j (0..255) {
			if ($tmp eq $sbox[$j]){$data.=chr($j);last};
		}
		#my %index;
		#@index{@sbox} = (0..$#sbox);
		#my $index = $index{$tmp};
		#$data.=chr($index);
	}
	print $outfile $data;$data="";
}
close($outfile);
close($infile);
}

sub sbox_gen {
my @sbox; my @sary=@_;
for my $i (0..255) {
	my $tmp=ord(substr($key,$i,1))**3;
	$tmp=$tmp%scalar(@sary);
	push @sbox,$sary[$tmp];
	splice(@sary,$tmp,1);
}
return @sbox;
}