Simple service class to encrypt and decrypt string using php5-mcrypt

EncryptionService.php

<?php
namespace Package\Key\Service;

use TYPO3\Flow\Annotations as Flow;

/**
 * Class EncryptionService
 *
 * @Flow\Scope("singleton")
 */
class EncryptionService {

	/**
	 * @Flow\Inject(setting="Package.Key.encryption.privateKey", package="Package.Key")
	 * @var string
	 */
	protected $privateKey;

	/**
	 * @param $string
	 * @return string
	 */
	public function encryptString($string) {
		$key = $this->privateKey;
		$string =  str_pad($string, 1, ' ', STR_PAD_BOTH);

		$iv = mcrypt_create_iv(
			mcrypt_get_iv_size(MCRYPT_RIJNDAEL_256, MCRYPT_MODE_CBC),
			MCRYPT_DEV_URANDOM
		);

		$encrypted = base64_encode(
			$iv .
			mcrypt_encrypt(
				MCRYPT_RIJNDAEL_256,
				hash('sha256', $key, true),
				$string,
				MCRYPT_MODE_CBC,
				$iv
			)
		);

		return $encrypted;
	}

	/**
	 * @param $string
	 * @return string
	 */
	public function decryptString($string) {
		$key = $this->privateKey;
		$encrypted = $string;
		$data = base64_decode($encrypted);
		$iv = substr($data, 0, mcrypt_get_iv_size(MCRYPT_RIJNDAEL_256, MCRYPT_MODE_CBC));
		$decrypted = rtrim(
			mcrypt_decrypt(
				MCRYPT_RIJNDAEL_256,
				hash('sha256', $key, true),
				substr($data, mcrypt_get_iv_size(MCRYPT_RIJNDAEL_256, MCRYPT_MODE_CBC)),
				MCRYPT_MODE_CBC,
				$iv
			),
			"\0"
		);
		return trim($decrypted);
	}

}