Mohammad S Anwar >
Crypt-Affine >
Crypt::Affine

Module Version: 0.08
Crypt::Affine - Interface to the Affine cipher.

Version 0.08

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

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 });

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";

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";

Mohammad S Anwar, `<mohammad.anwar at yahoo.com>`

https://github.com/manwar/Crypt-Affine

Please report any bugs/feature requests to `bug-crypt-affine at rt.cpan.org`

or through the web interface at 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.

You can find documentation for this module with the perldoc command.

perldoc Crypt::Affine

You can also look for information at:

- RT: CPAN's request tracker
- AnnoCPAN: Annotated CPAN documentation
- CPAN Ratings
- Search CPAN

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:

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