From 762b6ec2198fb8da3a4517c8bd412d423bc4ea93 Mon Sep 17 00:00:00 2001
From: Rongjian Lan <rongjian.lan@gmail.com>
Date: Sat, 4 Aug 2018 20:34:13 +0800
Subject: [PATCH] Aggregate responses and create schnorr multi-sig

---
 consensus/consensus.go        |  4 +++-
 consensus/consensus_leader.go | 20 +++++++++++++++++++-
 2 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/consensus/consensus.go b/consensus/consensus.go
index a62394b43..0cbab2fd3 100644
--- a/consensus/consensus.go
+++ b/consensus/consensus.go
@@ -18,7 +18,9 @@ import (
 type Consensus struct {
 	state ConsensusState
 	// Commits collected from validators. A map from node Id to its commitment
-	commitments map[uint16]kyber.Point
+	commitments          map[uint16]kyber.Point
+	aggregatedCommitment kyber.Point
+
 	// Commits collected from validators.
 	bitmap *crypto.Mask
 	// Responses collected from validators
diff --git a/consensus/consensus_leader.go b/consensus/consensus_leader.go
index deef1b4c5..9062c78f1 100644
--- a/consensus/consensus_leader.go
+++ b/consensus/consensus_leader.go
@@ -221,6 +221,7 @@ func (consensus *Consensus) constructChallengeMessage() []byte {
 
 	// 32 byte challenge
 	buffer.Write(getChallenge(aggCommitment, consensus.bitmap.AggregatePublic, buffer.Bytes()[:36])) // message contains consensus id and block hash for now.
+	consensus.aggregatedCommitment = aggCommitment
 
 	// 64 byte of signature on previous data
 	signature := consensus.signMessage(buffer.Bytes())
@@ -325,6 +326,23 @@ func (consensus *Consensus) processResponseMessage(payload []byte) {
 	if len(consensus.responses) >= (2*len(consensus.validators))/3+1 && consensus.state != FINISHED {
 		consensus.mutex.Lock()
 		if len(consensus.responses) >= (2*len(consensus.validators))/3+1 && consensus.state != FINISHED {
+			// Aggregate responses
+			responses := make([]kyber.Scalar, 0)
+			for _, val := range consensus.responses {
+				responses = append(responses, val)
+			}
+			aggResponse, err := crypto.AggregateResponses(crypto.Ed25519Curve, responses)
+			if err != nil {
+				log.Error("Failed to aggregate responses")
+				return
+			}
+			collectiveSign, err := crypto.Sign(crypto.Ed25519Curve, consensus.aggregatedCommitment, aggResponse, consensus.bitmap)
+			if err != nil {
+				log.Error("Failed to create collective signature")
+				return
+			}
+			_ = collectiveSign // TODO: put the collective signature into block and broadcast
+
 			consensus.Log.Debug("Consensus reached with signatures.", "numOfSignatures", len(consensus.responses))
 			// Reset state to FINISHED, and clear other data.
 			consensus.ResetState()
@@ -335,7 +353,7 @@ func (consensus *Consensus) processResponseMessage(payload []byte) {
 			// For now, we used the stored whole block already stored in consensus.blockHeader
 			txDecoder := gob.NewDecoder(bytes.NewReader(consensus.blockHeader))
 			var blockHeaderObj blockchain.Block
-			err := txDecoder.Decode(&blockHeaderObj)
+			err = txDecoder.Decode(&blockHeaderObj)
 			if err != nil {
 				consensus.Log.Debug("failed to construct the new block after consensus")
 			}