public static bool DecryptMulticastFrame(MpanTable mpanTable, MulticastKey multicastKey, NodeGroupId nodeGroupId, byte[] homeId, COMMAND_CLASS_SECURITY_2.SECURITY_2_MESSAGE_ENCAPSULATION cmd, out byte[] data, out Extensions extensions)
{
List <COMMAND_CLASS_SECURITY_2.SECURITY_2_MESSAGE_ENCAPSULATION.TVG1> encryptedExtensionsList = new List <COMMAND_CLASS_SECURITY_2.SECURITY_2_MESSAGE_ENCAPSULATION.TVG1>();
List <COMMAND_CLASS_SECURITY_2.SECURITY_2_MESSAGE_ENCAPSULATION.TVG1> extensionsList = new List <COMMAND_CLASS_SECURITY_2.SECURITY_2_MESSAGE_ENCAPSULATION.TVG1>();
extensions = null;
data = null;
bool ret = false;
extensionsList = cmd.vg1;
if (mpanTable.CheckMpanExists(nodeGroupId) && !mpanTable.IsRecordInMOSState(nodeGroupId))
{
// Backup mpan.
byte seqNo = mpanTable[nodeGroupId].SequenceNumber;
byte[] mpanBackup = new byte[mpanTable[nodeGroupId].MpanState.Length];
Array.Copy(mpanTable[nodeGroupId].MpanState, mpanBackup, mpanTable[nodeGroupId].MpanState.Length);
// Try to decrypt.
bool decryptSucceeded = false;
int attempts = 0;
byte[] plainData = null;
while (!decryptSucceeded && attempts < MaxMpanIterations)
{
var mpan = new byte[16];
if (IncrementMpan(mpanTable, multicastKey, nodeGroupId, mpan))
{
decryptSucceeded = DecryptS2(multicastKey.CcmKey,
mpan,
nodeGroupId.NodeId,
nodeGroupId.GroupId,
homeId,
cmd,
out plainData,
out encryptedExtensionsList);
}
attempts++;
}
if (decryptSucceeded)
{
extensions = new Extensions
{
ExtensionsList = extensionsList ?? new List <COMMAND_CLASS_SECURITY_2.SECURITY_2_MESSAGE_ENCAPSULATION.TVG1>(),
EncryptedExtensionsList = encryptedExtensionsList ?? new List <COMMAND_CLASS_SECURITY_2.SECURITY_2_MESSAGE_ENCAPSULATION.TVG1>()
};
ret = true;
data = plainData;
}
else
{
var restoredMpanContainer = mpanTable.AddOrReplace(nodeGroupId, seqNo, null, mpanBackup);
}
}
return(ret);
}
public static bool IncrementMpan(MpanTable mpanTable, MulticastKey multicastKey, NodeGroupId nodeGroupId, byte[] outMpan)
{
if (mpanTable.CheckMpanExists(nodeGroupId) && !mpanTable.IsRecordInMOSState(nodeGroupId))
{
var container = mpanTable[nodeGroupId];
SecurityS2Utils.Aes128EcbEncrypt(container.MpanState, multicastKey.MpanKey, outMpan);
container.IncrementMpanState();
container.UpdateSequenceNumber();
return(true);
}
return(false);
}