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# Create script to implement Chaocipher. Please checkout wiki page for more information
# Visualizing it using rotating disk is a bit difficult, here's a video illustration of the algo
# https://www.youtube.com/watch?v=0tL9A69olRc , that helped me understand it
use strict;
use warnings;
use 5.010;
die "Usage:\n\tch-2.pl <-d|e> \"<string to encrypt>\"\n\n" if @ARGV<2;
my $encrypt = $ARGV[0] eq '-e';
my $text_string = $ARGV[1];
#It should be okay to modify the zenith/nadir (0 to $wheelsize)
use constant ZENITH => 0;
use constant NADIR => 13;
#Initialize wheels (chaocipher with bigger wheels!)
my @pt = "7bqkj9l2hOWyzA8SLPEtRvBwUQVmxa45g ufspeTF1KHd0DrGMCZoJXi3YIN6nc"=~/./g;
my @ct = "vEDclCHZYeWo9drb6Jnkf5MRXOt UgN4Fi231GzQIx7sPaLK8TBuVpA0yjShqwm"=~/./g;
my $wheel_size = $#pt;
# This function rotates the given array or a portion of the given array
# Rotation count is defined by $r
# The whole array will be rotated by default
# but the range can be specified in $from and $to variable
sub rot {
my ($r,$array, $from, $to) = @_;
$r %= ($wheel_size+1);
return if $r == 0;
if (!(defined $to && defined $from)) {
@{$array} = (@{$array}[$r..$#{$array}], @{$array}[0..~-$r]);
} else {
$r += $from;
@{$array} = (@{$array}[0..~-$from], @{$array}[$r..$to], @{$array}[$from..~-$r],@{$array}[$to+1..$#{$array}]);
}
}
sub cipher {
my ($text,$enc,$ret) = @_;
for my $c ($text=~/./g) {
#find where $c is in the plain text @pt (or @ct when decrypting)
#grep wont stop when first occurence was found
my $pt_pos = (grep {($enc?$pt[$_]:$ct[$_]) eq $c} 0..$wheel_size)[0];
#Get the character from the cipher text in that position($pt_pos)
$ret .= $enc?$ct[$pt_pos]:$pt[$pt_pos];
#rotate @pt and @ct from $pt_pos to ZENITH
&rot($pt_pos-ZENITH, \@pt);
&rot($pt_pos-ZENITH, \@ct);
#permute @ct: move the char in ZENITH + 1 to NADIR
&rot(1,\@ct,ZENITH+1,NADIR);
#permute @pt: rotate1 then move the char in ZENITH + 2 to NADIR
&rot(1,\@pt);
&rot(1,\@pt,ZENITH+2,NADIR);
}
return $ret;
}
say &cipher($text_string,$encrypt);
=begin
perl .\ch-2.pl -e "a quick brown fox jumps over the lazy dog"
gFv4ujqOyIPdTk5I9bKrYUXY4DwkCygHDKmQmyqUh
perl .\ch-2.pl -d "gFv4ujqOyIPdTk5I9bKrYUXY4DwkCygHDKmQmyqUh"
a quick brown fox jumps over the lazy dog
=cut
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