private ConsensusMessage CreateEchoMessage(ValMessage valMessage)
{
return(new ConsensusMessage
{
EchoMessage = new ECHOMessage
{
SenderId = _broadcastId.SenderId,
MerkleTreeRoot = valMessage.MerkleTreeRoot,
Data = valMessage.Data,
MerkleProof = { valMessage.MerkleProof }
}
});
}
private ValMessage[] ConstructValMessages(IReadOnlyList <byte> input)
{
var shards = ErasureCodingShards(input, N, 2 * F);
var merkleTree = ConstructMerkleTree(shards);
var result = new ValMessage[N];
for (var i = 0; i < N; ++i)
{
result[i] = new ValMessage
{
SenderId = _broadcastId.SenderId,
MerkleTreeRoot = merkleTree[1],
MerkleProof = { MerkleTreeBranch(merkleTree, i) },
Data = ByteString.CopyFrom(shards[i]),
};
}
return(result);
}
private void HandleValMessage(ValMessage val, int validator)
{
var validatorPubKey = Wallet.EcdsaPublicKeySet[validator].ToHex();
if (_sentValMessage[validator])
{
Logger.LogWarning($"{Id}: validator {validator} ({validatorPubKey}) tried to send VAL message twice");
return;
}
Logger.LogTrace(
$"Protocol {Id} got VAL message from {validator} ({validatorPubKey}), sending ECHO"
);
_sentValMessage[validator] = true;
// Before sending echo, we can check if validator == val.SenderId, means if the val message is from the correct validator
// Because one validator cannot produce val message of another validator, it can only send echo.
// If we don't check this condition, there could be potential issue, for example, a malicious validator (id = x) sends a
// val message that has random shards but correct MerkleProof and uses val.SenderId = y (another validator), and sends to
// validator with id = z. It will be constructed as echo message and sent to everyone by validator, id = z, this echo will
// pass the CheckEchoMessage(). Now every honest validator will think that val message of validator of id = y is confirmed
// by echo message from validator of id = z. When the correct val message of id = y will come to id = z, he will send echo
// again but others will not accept it, because id = z already sent echo for id = y, (but it was from malicious id = x),
// because the correct echo for each pair is received only once.
if (validator == val.SenderId)
{
Broadcaster.Broadcast(CreateEchoMessage(val));
}
else
{
var pubKey = Broadcaster.GetPublicKeyById(validator) !.ToHex();
Logger.LogWarning(
$"Faulty behaviour: val message with sender id: {val.SenderId} came from validator: " +
$"{validator} ({pubKey}), which should not happen. Val message for {val.SenderId} should come " +
$"from {val.SenderId}. Not sending echo message for this val message");
}
}
