function _encryption_algorithm_to_crypt_instance($algorithm)
    {
        switch ($algorithm) {
            case '3des-cbc':
                return new TripleDES();
            case '3des-ctr':
                return new TripleDES(Base::MODE_CTR);
            case 'aes256-cbc':
            case 'aes192-cbc':
            case 'aes128-cbc':
                return new Rijndael();
            case 'aes256-ctr':
            case 'aes192-ctr':
            case 'aes128-ctr':
                return new Rijndael(Base::MODE_CTR);
            case 'blowfish-cbc':
                return new Blowfish();
            case 'blowfish-ctr':
                return new Blowfish(Base::MODE_CTR);
            case 'twofish128-cbc':
            case 'twofish192-cbc':
            case 'twofish256-cbc':
            case 'twofish-cbc':
                return new Twofish();
            case 'twofish128-ctr':
            case 'twofish192-ctr':
            case 'twofish256-ctr':
                return new Twofish(Base::MODE_CTR);
            case 'arcfour':
            case 'arcfour128':
            case 'arcfour256':
                return new RC4();
        }
        return null;
    }