Cipher Implementation

Content:

• Installation
• Usage and Extending
• KPA
• Testing

This package presents a basic cipher implementation using OOP practices. The main goal is to demonstrate a way how OOP can be helpful implementing such a mechanism.

Installation

This project requires the presence of these softwares:

• php
• composer, php's package manager

Then run the command in the root directory to install required packages:

# if composer is locally installed
php .\composer.phar install

# if globally
composer install

Usage and Extending

The App\Provider\CipherServiceProvider is a simple factory which creates a cipher. The cipher's capability to decrypt/encrypt payload relies on its dependencies.

It depends on the App\LookupTable\LookupTableDTO which statically holds the lookup table and provides bi-directional access to its content. At this current state it assumes that the DTO is created form (indexed) array. Thus its method names are representing this behaviour. Because the DTO is tightly coupled to the cipher factory changing its method names requires refactoring in other parts of the codebase.

It also needs a cryptographer which implements the CryptographerInterface. This contains the concrete implementation of the encryption/decryption logic.

App\LookupTable\LookupTableDTO is tightly coupled with the CryptographerInterface too. Watch out for changes in DTO methods!

Additionally it can accept a secret key, but this can also be injected when calling its methods, since it is a good practice to provide a new secret key to each message.

KPA

The App\Attacker\KPAttacker can be used with a cryptographer which implements the App\Attacker\KPACryptanalyserInterface. It also needs an array of encrypted messages, an instance of the App\LookupTable\LookupTableDTO and a dictionary.

Testing

The App\Cryptographer\BasicCryptographer class is used to test both the App\Provider\CipherServiceProvider and the App\Attacker\KPAttacker. These tests can be found in the ./tests directory.

This project uses the PHPUnit framework for testing.

To run all tests use this command: php .\vendor\bin\phpunit .\tests\ --color