// This function is only called by fillBlameMatrix to collect messages sent in
// phases 1, 2, and 3. and to organize the information appropriately.
// If the function returns false, this means that packets has an invalid format.
private static boolean fillBlameMatrixCollectHistory(
VerificationKey vk,
VerificationKey from,
Queue<Packet> packets,
Matrix matrix,
// The messages sent in the broadcast phase by the last player to all the other players.
Map<VerificationKey, Packet> outputVectors,
// The list of messages history in phase 2.
Map<VerificationKey, Packet> shuffleMessages,
// The keys received by everyone in the announcement phase.
Map<VerificationKey, EncryptionKey> receivedKeys,
// The keys sent by everyone in the announcement phase.
Map<VerificationKey, Map<VerificationKey, EncryptionKey>> sentKeys)
throws FormatException {
if (packets == null) return false;
boolean validPacket = true;
// Collect all packets received in the appropriate place.
for (Packet packet : packets) {
switch (packet.phase()) {
case BroadcastOutput:
{
if (outputVectors.containsKey(from)) {
// We should only ever receive one such message from each player.
if (outputVectors.containsKey(from) && !outputVectors.get(from).equals(packet)) {
log.error(
"Player "
+ vk.toString()
+ " null blames "
+ from.toString()
+ ", case A; "
+ outputVectors.get(from).toString()
+ " != "
+ packet.toString());
matrix.put(vk, Evidence.Liar(from, new Packet[] {outputVectors.get(from), packet}));
}
} else {
outputVectors.put(from, packet);
}
break;
}
case Announcement:
{
Map<VerificationKey, EncryptionKey> map = sentKeys.get(packet.from());
if (map == null) {
map = new HashMap<>();
sentKeys.put(packet.from(), map);
}
EncryptionKey key = packet.payload().readEncryptionKey();
map.put(from, key);
receivedKeys.put(packet.from(), key);
break;
}
case Shuffling:
{
if (shuffleMessages.containsKey(from) && !shuffleMessages.get(from).equals(packet)) {
matrix.put(vk, Evidence.Liar(from, new Packet[] {shuffleMessages.get(from), packet}));
} else {
shuffleMessages.put(from, packet);
}
break;
}
default:
{
// This case should never happen.
// It's not malicious but it's not allowed either.
validPacket = false;
}
}
}
return validPacket;
}
// When we know we'll receive a bunch of blame messages, we have to go through them all
// to figure out what's going on.
final Matrix fillBlameMatrix() throws IOException, InterruptedException, FormatException {
Matrix matrix = new Matrix();
Map<VerificationKey, Queue<Packet>> blameMessages = mailbox.receiveAllBlame();
// Get all hashes received in phase 4 to check that they were reported correctly.
Map<VerificationKey, Message> hashes = new HashMap<>();
{
Queue<Packet> hashMessages = mailbox.getPacketsByPhase(Phase.EquivocationCheck);
for (Packet packet : hashMessages) {
hashes.put(packet.from(), packet.payload());
}
// Include my own hash.
hashes.put(vk, equivocationCheckHash(players, encryptionKeys, newAddresses));
}
// The messages sent in the broadcast phase by the last player to all the other players.
Map<VerificationKey, Packet> outputVectors = new HashMap<>();
// The encryption keys sent from every player to every other.
Map<VerificationKey, Map<VerificationKey, EncryptionKey>> sentKeys = new HashMap<>();
// The list of messages history in phase 2.
Map<VerificationKey, Packet> shuffleMessages = new HashMap<>();
// The set of decryption keys from each player.
Map<VerificationKey, DecryptionKey> decryptionKeys = new HashMap<>();
// Determine who is being blamed and by whom.
for (Map.Entry<VerificationKey, Queue<Packet>> entry : blameMessages.entrySet()) {
VerificationKey from = entry.getKey();
Queue<Packet> responses = entry.getValue();
for (Packet packet : responses) {
Message message = packet.payload();
if (message.isEmpty()) {
log.error("Empty blame message received from " + from);
matrix.put(vk, Evidence.InvalidFormat(from, packet));
}
while (!message.isEmpty()) {
Blame blame = message.readBlame();
message = message.rest();
switch (blame.reason) {
case InsufficientFunds:
{
// Is the evidence included sufficient?
// TODO check whether this is a conflicting transaction.
matrix.put(from, Evidence.InsufficientFunds(blame.accused));
break;
}
// If there is an equivocation failure, all players must send a blame
// message containing the messages they received in phases 1 and 4.
case EquivocationFailure:
{
// These are the keys received by
// this player in the announcement phase.
Map<VerificationKey, EncryptionKey> receivedKeys = new HashMap<>();
if (!fillBlameMatrixCollectHistory(
vk,
from,
blame.packets,
matrix,
outputVectors,
shuffleMessages,
receivedKeys,
sentKeys)) {
matrix.put(from, Evidence.Liar(from, new Packet[] {packet}));
}
Queue<Address> addresses = new LinkedList<>();
// The last player will not have
// received a separate set of addresses for
// us to check, so we insert our own.
if (from.equals(players.get(N))) {
addresses = newAddresses;
} else {
Message output = outputVectors.get(from).payload();
while (!output.isEmpty()) {
addresses.add(output.readAddress());
output = output.rest();
}
}
// If the sender is not player one, we add the keys he sent us,
// as he would not have received any set of keys from himself.
if (!from.equals(players.get(1))) {
receivedKeys.put(from, encryptionKeys.get(from));
}
// Check if this player correctly reported
// the hash previously sent to us.
Message newHash = equivocationCheckHash(players, receivedKeys, addresses);
if (newHash == null || !hashes.get(from).equals(newHash)) {
matrix.put(vk, Evidence.Liar(from, new Packet[] {packet}));
}
break;
}
case ShuffleAndEquivocationFailure:
{
if (!decryptionKeys.containsKey(from)) {
// We should not receive two keys from the same player so this
// block should always execute in a perfect world.
decryptionKeys.put(from, blame.privateKey);
}
// Check that the decryption key is valid. (The decryption key
// can be null for player 1, who doesn't make one.)
if (!packet.from().equals(players.get(1))) {
if (blame.privateKey == null) {
matrix.put(vk, Evidence.InvalidFormat(from, packet));
} else if (!blame.privateKey.EncryptionKey().equals(encryptionKeys.get(from))) {
// We have received a private key that does not match
// the public key we have for this player. Include the
// original packet containing the encryption key and the
// packet with the mismatched key.
Packet newKeyPacket = null;
Queue<Packet> newKeyPackets = mailbox.getPacketsByPhase(Phase.Announcement);
for (Packet p : newKeyPackets) {
if (p.from().equals(packet.from())) {
newKeyPacket = p;
}
}
matrix.put(vk, Evidence.Liar(from, new Packet[] {newKeyPacket, packet}));
}
}
if (!fillBlameMatrixCollectHistory(
vk,
from,
blame.packets,
matrix,
outputVectors,
shuffleMessages,
new HashMap<VerificationKey, EncryptionKey>(),
sentKeys)) {
matrix.put(vk, Evidence.Liar(from, new Packet[] {packet}));
}
break;
}
case DoubleSpend:
{
// TODO does this actually spend the funds?
matrix.put(from, Evidence.DoubleSpend(blame.accused, blame.t));
break;
}
case InvalidSignature:
{
if (blame.invalid == null || blame.accused == null) {
matrix.put(vk, Evidence.Liar(from, new Packet[] {packet}));
break;
}
// TODO do we agree that the signature is invalid?
matrix.put(from, Evidence.InvalidSignature(blame.accused, blame.invalid));
break;
}
// These should already have been handled.
case MissingOutput:
{
break;
}
case ShuffleFailure:
{
break;
}
default:
matrix.put(vk, Evidence.Placeholder(from, Reason.InvalidFormat));
}
}
}
}
// Check that we have all the required announcement messages.
if (sentKeys.size() > 0) {
for (int i = 2; i < players.size(); i++) {
if (i == me) {
continue;
}
VerificationKey from = players.get(i);
Map<VerificationKey, EncryptionKey> sent = sentKeys.get(from);
if (sent == null) {
// This should not really happen.
continue;
}
// Add in the key I received from this player.
sent.put(vk, encryptionKeys.get(from));
EncryptionKey key = null;
for (int j = 1; j <= players.size(); j++) {
if (i == j) {
continue;
}
VerificationKey to = players.get(j);
EncryptionKey next = sent.get(to);
if (next == null) {
// blame player to. He should have sent us this.
matrix.put(vk, Evidence.Placeholder(to, Reason.Liar));
continue;
}
if (key != null && !key.equals(next)) {
matrix.put(vk, Evidence.EquivocationFailureAnnouncement(from, sent));
break;
}
key = next;
}
}
}
boolean outputEquivocate = false;
if (outputVectors.size() > 0) {
// Add our own vector to this.
if (me != N) {
outputVectors.put(vk, mailbox.getPacketsByPhase(Phase.BroadcastOutput).peek());
}
// We should have one output vector for every player except the last and ourselves.
Set<VerificationKey> leftover = playerSet(1, N - 1);
leftover.removeAll(outputVectors.keySet());
if (leftover.size() > 0) {
for (VerificationKey key : leftover) {
// matrix.put(vk, Evidence.Placeholder(key, Reason.Liar));
}
}
List<Message> outputMessages = new LinkedList<>();
for (Packet packet : outputVectors.values()) {
outputMessages.add(packet.payload());
}
// If they are not all equal, blame the last player for equivocating.
if (!areEqual(outputMessages)) {
matrix.put(vk, Evidence.EquivocationFailureBroadcast(players.get(N), outputVectors));
outputEquivocate = true;
}
}
if (decryptionKeys.size() > 0) {
// We should have one decryption key for every player except the first.
Set<VerificationKey> leftover = playerSet(2, players.size());
leftover.removeAll(decryptionKeys.keySet());
if (leftover.size() > 0) {
log.warn("leftover");
// TODO blame someone.
} else {
Evidence shuffleEvidence =
checkShuffleMisbehavior(
players,
decryptionKeys,
shuffleMessages,
outputEquivocate ? null : outputVectors);
if (shuffleEvidence != null) {
matrix.put(vk, shuffleEvidence);
}
}
}
return matrix;
}