package Crypt::Affine;
$Crypt::Affile::VERSION = '0.07';
=head1 NAME
Crypt::Affine - Interface to the Affine cipher.
=head1 VERSION
Version 0.07
=cut
use 5.006;
use autodie;
use Data::Dumper;
use Crypt::Affine::Params qw($Num $FilePath $ZeroOrOne);
use Moo;
use namespace::clean;
=head1 DESCRIPTION
The affine cipher is a type of mono alphabetic substitution cipher, wherein each
letter in an alphabet is mapped to its numeric equivalent & then encrypted using
a simple mathematical function. It inherits the weaknesses of all substitution
ciphers. In the affine cipher the letters of an alphabet of size m are first
mapped to the integers in the range 0..m-1. It then uses modular arithmetic to
transform the integer that each plaintext letter corresponds to into another
integer that correspond to a ciphertext letter.The function for encryption of a
single letter can be defined as below:
E(x) = (mx + r) % l
where 'l' is the size of the alphabet and 'm' & 'r' are the key of cipher. The
value 'm' must be choosen such that 'm' and 'l' are coprime.
Similarly the function for decryption of a single letter can be defined as below:
D(x) = (m ^ -1) (x - r) % l
where (m ^ -1) is the modular multiplicative inverse of 'm' modulo 'l' and it
satisfies the equation below:
m (m ^ -1) % l = 1
=cut
has 'm' => (is => 'ro', isa => $Num, required => 1 );
has 'r' => (is => 'ro', isa => $Num, required => 1 );
has 'reverse' => (is => 'ro', isa => $ZeroOrOne, default => sub { return 0; });
has 'source' => (is => 'ro', isa => $FilePath);
=head1 CONSTRUCTOR
The constructor expects the following parameters as described below in the table:
+----------+----------+-------------------------------------------------+
| Key | Required | Description |
+----------+----------+-------------------------------------------------+
| m | Yes | Any positive number. |
| r | Yes | Any positive number. |
| reverse | No | 0 or 1, depending whether to use reverse set of |
| | | alphabets. Default is 0. |
| source | No | Filename with complete path containing comma |
| | | separated list of alphabets. By default it uses |
| | | A-Z, a-z. |
+----------+----------+-------------------------------------------------+
use strict; use warnings;
use Crypt::Affine;
my $affine = Crypt::Affine->new({ m => 5, r => 8 });
=head1 METHODS
=head2 encrypt()
Encrypts the given string of alphabets ignoring any non-alphabets.
use strict; use warnings;
use Crypt::Affine;
my $affine = Crypt::Affine->new({ m => 5, r => 8 });
my $original = 'affine cipher';
my $encrypted = $affine->encrypt($original);
print "Original : [$original]\n";
print "Encrypted: [$encrypted]\n";
=cut
sub encrypt {
my ($self, $data) = @_;
return unless defined $data;
$self->_prepare() unless defined $self->{_a};
my $encrypt = '';
foreach (split //,$data) {
(_unsupported($_))
?
($encrypt .= $_)
:
($encrypt .= $self->_encrypt($_));
}
return $encrypt;
}
=head2 decrypt()
Decrypts the given string of alphabets ignoring any non-alphabets.
use strict; use warnings;
use Crypt::Affine;
my $affine = Crypt::Affine->new({ m => 5, r => 8 });
my $original = 'affine cipher';
my $encrypted = $affine->encrypt('affine cipher');
my $decrypted = $affine->decrypt($encrypted);
print "Original : [$original]\n";
print "Encrypted: [$encrypted]\n";
print "Decrypted: [$decrypted]\n";
=cut
sub decrypt {
my ($self, $data) = @_;
return unless defined $data;
$self->_prepare() unless defined $self->{_a};
my $decrypt = '';
foreach (split //,$data) {
(_unsupported($_))
?
($decrypt .= $_)
:
($decrypt .= $self->_decrypt($_));
}
return $decrypt;
}
sub _prepare {
my ($self) = @_;
my @data = ();
my ($i, $j) = (1, 1);
my ($a_, $z_, $l_, %_a, %_z, $_data);
if (defined($self->{'source'}) && (-e $self->{'source'})) {
local undef $/;
open(my $IN, $self->{'source'});
$_data = <$IN>;
close($IN);
chomp $_data;
@data = split /\,/,$_data;
}
@data = ('a'..'z', 'A'..'Z') unless scalar(@data);
$l_ = scalar(@data);
foreach (@data) {
$a_->{$_} = $i++;
$z_->{$_} = ($l_ + 1) - $j++;
}
$self->{'r'} = $l_ if ($self->{'r'} > abs($l_));
%_a = reverse %{$a_};
%_z = reverse %{$z_};
$self->{'a_'} = $a_;
$self->{'z_'} = $z_;
$self->{'l_'} = $l_;
$self->{'_a'} = \%_a;
$self->{'_z'} = \%_z;
}
sub _encrypt {
my ($self, $char) = @_;
my $i = (($self->{'m'} * $self->{'a_'}->{$char}) + $self->{'r'}) % $self->{'l_'};
$i = $self->{'l_'} if ($i == 0);
(defined($self->{'reverse'}) && ($self->{'reverse'}))
?
return $self->{'_z'}->{$i}
:
return $self->{'_a'}->{$i};
}
sub _decrypt {
my ($self, $char) = @_;
my $i = 0;
my $j = 0;
(defined($self->{'reverse'}) && ($self->{'reverse'}))
?
($i = $self->{'z_'}->{$char})
:
($i = $self->{'a_'}->{$char});
$j = (_multiplier($self->{'m'}, $self->{'l_'}) * ($i - $self->{'r'})) % $self->{'l_'};
$j = $self->{'l_'} if ($j == 0);
return $self->{'_a'}->{$j};
}
sub _unsupported {
my ($byte) = @_;
return 1 if ($byte =~ /[\#\+\%\&\=\,\;\:\!\?\.\"\'\-\<\>\(\)\[\]\@\\\_\s]/);
return 0;
}
sub _multiplier {
my ($a, $m) = @_;
$m = abs($m);
$a = $a % $m;
my ($b, $x, $y, $n) = ($m, 1, 0);
while ($a != 0) {
$n = int($b / $a);
($a, $b, $x, $y) = ($b - $n * $a, $a, $y - $n * $x, $x);
}
return $y % $m;
}
=head1 AUTHOR
Mohammad S Anwar, C<< <mohammad.anwar at yahoo.com> >>
=head1 REPOSITORY
L<https://github.com/Manwar/Crypt-Affine>
=head1 BUGS
Please report any bugs/feature requests to C<bug-crypt-affine at rt.cpan.org> or
through the web interface at L<http://rt.cpan.org/NoAuth/ReportBug.html?Queue=Crypt-Affine>.
I will be notified & then you'll automatically be notified of progress on your bug
as I make changes.
=head1 SUPPORT
You can find documentation for this module with the perldoc command.
perldoc Crypt::Affine
You can also look for information at:
=over 4
=item * RT: CPAN's request tracker
L<http://rt.cpan.org/NoAuth/Bugs.html?Dist=Crypt-Affine>
=item * AnnoCPAN: Annotated CPAN documentation
L<http://annocpan.org/dist/Crypt-Affine>
=item * CPAN Ratings
L<http://cpanratings.perl.org/d/Crypt-Affine>
=item * Search CPAN
L<http://search.cpan.org/dist/Crypt-Affine/>
=back
=head1 LICENSE AND COPYRIGHT
Copyright (C) 2011 - 2015 Mohammad S Anwar.
This program is free software; you can redistribute it and/or modify it under
the terms of the the Artistic License (2.0). You may obtain a copy of the full
license at:
L<http://www.perlfoundation.org/artistic_license_2_0>
Any use, modification, and distribution of the Standard or Modified Versions is
governed by this Artistic License.By using, modifying or distributing the Package,
you accept this license. Do not use, modify, or distribute the Package, if you do
not accept this license.
If your Modified Version has been derived from a Modified Version made by someone
other than you,you are nevertheless required to ensure that your Modified Version
complies with the requirements of this license.
This license does not grant you the right to use any trademark, service mark,
tradename, or logo of the Copyright Holder.
This license includes the non-exclusive, worldwide, free-of-charge patent license
to make, have made, use, offer to sell, sell, import and otherwise transfer the
Package with respect to any patent claims licensable by the Copyright Holder that
are necessarily infringed by the Package. If you institute patent litigation
(including a cross-claim or counterclaim) against any party alleging that the
Package constitutes direct or contributory patent infringement,then this Artistic
License to you shall terminate on the date that such litigation is filed.
Disclaimer of Warranty: THE PACKAGE IS PROVIDED BY THE COPYRIGHT HOLDER AND
CONTRIBUTORS "AS IS' AND WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES. THE IMPLIED
WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, OR
NON-INFRINGEMENT ARE DISCLAIMED TO THE EXTENT PERMITTED BY YOUR LOCAL LAW. UNLESS
REQUIRED BY LAW, NO COPYRIGHT HOLDER OR CONTRIBUTOR WILL BE LIABLE FOR ANY DIRECT,
INDIRECT, INCIDENTAL, OR CONSEQUENTIAL DAMAGES ARISING IN ANY WAY OUT OF THE USE
OF THE PACKAGE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
=cut
1; # End of Crypt::Affine