/**
* Determine if the MAC for the given payload is valid.
*
* @param array $payload
* @return bool
*
* @throws \RuntimeException
*/
protected function validMac(array $payload)
{
$bytes = Str::randomBytes(16);
$calcMac = hash_hmac('sha256', $this->hash($payload['iv'], $payload['value']), $bytes, true);
return Str::equals(hash_hmac('sha256', $payload['mac'], $bytes, true), $calcMac);
}