private function getMac($messageVersion, $senderIdentityKey, $receiverIdentityKey, $macKey, $serialized)
{
$mac = hash_init("sha256", HASH_HMAC, $macKey);
if ($messageVersion >= 3) {
hash_update($mac, $senderIdentityKey->getPublicKey()->serialize());
hash_update($mac, $receiverIdentityKey->getPublicKey()->serialize());
}
hash_update($mac, $serialized);
$result = hash_final($mac, true);
return ByteUtil::trim($result, self::MAC_LENGTH);
}
