perl: Chaocipher

chaocipher.perl

# ChaoSim.pl : Simulation of Chaocipher enciphering/deciphering
# (c) Moshe Rubin, August 2010
# email: mosher@mountainvistasoft.com
use strict;
use diagnostics;
use warnings;
my $left = uc($ARGV[1]);
my $right = uc($ARGV[2]);
my $mode = $ARGV[3];
my $pt = "";
my $ct = "";
my $len = 0;
my $trace = 0;
if (scalar(@ARGV) == 0)
{
usage();
exit (-1);
}
if (exists ($ARGV[4]))
{
$trace = 1;
}
# Read input file
if ($mode eq "encipher")
{
$pt = getFile ($ARGV[0]);
$len = length($pt);
}
else
{
$ct = getFile ($ARGV[0]);
$len = length($ct);
}
printf "\n";
printf "Left: $left Right: $right";
for (my $i=0; $i<$len; ++$i)
{
my $p;
my $c;
my $shift;
if ($mode eq "encipher")
{
# Encipher plaintext letter
$p = substr ($pt, $i, 1);
($right, $shift) = bringToZenith ($right, $p);
$left = rotate ($left, $shift);
$c = substr ($left, 0, 1);
$ct .= $c;
}
else
{
# Decipher ciphertext letter
$c = substr ($ct, $i, 1);
($left, $shift) = bringToZenith ($left, $c);
$right = rotate ($right, $shift);
$p = substr ($right, 0, 1);
$pt .= $p;
}
printf " ($p,$c)\n" if $trace;
# Permute alphabets
$left = permute ($left, 1);
$right = rotate ($right, 1);
$right = permute ($right, 2);
printf "Left: $left Right: $right" if $trace;
}Chaocipher Revealed: The Algorithm 2
printf "\n\n";
printf "Plaintext: $pt\n";
printf "\n";
printf "Ciphertext: $ct\n";
sub getFile
{
my ($f) = @_;
my $text = "";
my $line;
open (FILE, "<$f");
while ($line = <FILE>)
{
chomp($line);
$line =~ s/\s+//g;
$line = uc($line);
$text .= $line;
}
close (FILE);
return $text;
}
sub bringToZenith
{
# Bring letter to zenith position
my ($alphabet, $letter) = @_;
my $index = index ($alphabet, $letter);
return (rotate ($alphabet, $index), $index);
}
sub rotate
{
# Rotate alphabet N positions counterclockwise
my ($alphabet, $shift) = @_;
return ($shift > 0) ?
substr ($alphabet, $shift) . substr ($alphabet, 0, $shift) :
$alphabet;
}
sub permute
{
# Generic Chaocipher alphabet permutation (i.e., Nick Pelling's "twizzling")
my ($alphabet, $offset) = @_;
return substr ($alphabet, 0, $offset) .
substr ($alphabet, $offset+1, 13-$offset) .
substr ($alphabet, $offset, 1) .
substr ($alphabet, 14);
}
sub usage
{
printf "Usage: perl ChaoSim.pl <input_file> <left_alphabet> <right_alphabet>\n";
printf " <'encipher' | 'decipher'> [trace]\n\n";
printf "Example: perl ChaoSim.pl my.ct.txt emkxgdclirwpvqutnbjshyaozf\n";
printf " zpjkelbohdtycavirufmnxgqsw decipher\n\n";
printf " perl ChaoSim.pl my.pt.txt bfurkashexcymnvqzgijtldwpo\n";
printf " uslfieavpdcybjzthogkmnxwqr encipher 1\n";