Hash method body

protected function hash($iv, $value)
    {
        return hash_hmac('sha256', $iv.$value, $this->key);
    }    
```
i.e. the SHA256 hashing of the concatenation of IV and value, using the provided encryption key.
4. An array containing `iv`, `value` and `mac` is generated and converted to json (line `16`)
5. The json is encoded in base64 and finally returned (line `22`)

### How decryption works - in depth

To understand how clear data is recovered, let's give a closer look to the `decrypt()` method:

```
    public function decrypt($payload, $unserialize = true)
    {
        $payload = $this->getJsonPayload($payload);

        $iv = base64_decode($payload['iv']);

        // Here we will decrypt the value. If we are able to successfully decrypt it
        // we will then unserialize it and return it out to the caller. If we are
        // unable to decrypt this value we will throw out an exception message.
        $decrypted = \openssl_decrypt(
            $payload['value'], $this->cipher, $this->key, 0, $iv
        );

        if ($decrypted === false) {
            throw new DecryptException('Could not decrypt the data.');
        }

        return $unserialize ? unserialize($decrypted) : $decrypted;
    }