[19JUN15] Encryption exercise

enigma.php

<?php

namespace Enigma;


class Encrypt {
    protected $_cyphertext;
    protected $_salt;
    protected $_iv;
    protected $_vernamtext;
    protected $_outputtext;
    
    public function __construct($plaintext, $password)
    {
        // Generate key and IV
        $key = openssl_random_pseudo_bytes(32);
        $iv_size = mcrypt_get_iv_size(MCRYPT_RIJNDAEL_256, MCRYPT_MODE_CBC);
        $this->_iv = mcrypt_create_iv($iv_size, MCRYPT_RAND);

        // Encrypt immediately
        $this->_cyphertext = mcrypt_encrypt(MCRYPT_RIJNDAEL_256, $key, trim($plaintext), MCRYPT_MODE_CBC, $this->_iv);

        // Generate passphrase
        $this->_salt = openssl_random_pseudo_bytes(32);
        $passphrase = hash('sha256', $password.$this->_salt);
        $verify = hash('sha512', $plaintext.$this->_cyphertext.$this->_salt);

        // Generate Vernamtext
        $this->_vernamtext = $key ^ $passphrase;
        $this->_outputtext = implode(':', array(
            base64_encode($this->_salt),
            base64_encode($this->_iv),
            base64_encode($verify),
            base64_encode($this->_vernamtext),
            base64_encode($this->_cyphertext)
        ));
    }

    public function get()
    {
        return (is_null($this->_outputtext) ? false : $this->_outputtext);
    }

}

class Decrypt {
    protected $_plaintext;
    protected $_cyphertext;
    protected $_vernamtext;
    protected $_salt;
    protected $_iv;

    public function __construct(Encrypt $input, $password)
    {
        if (!$input->get()) {
            return;
        } else {
            $inputtext = $input->get();
        }

        // Split input into the right parts, get the right key
        list($salt, $iv, $verify, $vernamtext, $cyphertext) = explode(':', $inputtext);
        $this->_salt = base64_decode($salt);
        $this->_iv = base64_decode($iv);
        $verify = base64_decode($verify);
        $this->_vernamtext = base64_decode($vernamtext);
        $this->_cyphertext = base64_decode($cyphertext);

        $passphrase = hash('sha256', $password.$this->_salt);
        $key = $this->_vernamtext ^ $passphrase;

        // Decrypt the input
        $this->_plaintext = trim(mcrypt_decrypt(MCRYPT_RIJNDAEL_256, $key, $this->_cyphertext, MCRYPT_MODE_CBC, $this->_iv));

        // Generate verification
        if (hash('sha512', $this->_plaintext.$this->_cyphertext.$this->_salt) !== $verify) {
            $this->_plaintext = null;
            throw new \Exception('Decryption failed: could not verify data integrity. Password is probably wrong');
        }
    }

    public function get()
    {
        return (is_null($this->_plaintext) ? false : $this->_plaintext);
    }
}

unittest.php

<?php

require_once('./enigma.php');


$text = 'Here lies a test string. May it rest in peace!';
$password = 'MyP00rlyCreatedPassword!';

$hash = sha1(trim($text));

$encrypted = new Enigma\Encrypt($text, $password);
$decrypted = new Enigma\Decrypt($encrypted, $password);

$final = sha1(trim($decrypted->get()));

if ($final === $hash) {
	echo "\nOK.\n";
} else {
	echo "\nNOT OK.\n";
}