core: reset DKG if to less qualified nodes (#528)

3 files changed, 14 insertions, 5 deletions

diff --git a/core/configuration-chain_test.go b/core/configuration-chain_test.go
index a4c6e2a..0adfdcf 100644
--- a/core/configuration-chain_test.go
+++ b/core/configuration-chain_test.go
@@ -271,7 +271,7 @@ func (s *ConfigurationChainTestSuite) preparePartialSignature(
 // All participants are good people in this test.
 func (s *ConfigurationChainTestSuite) TestConfigurationChain() {
 	k := 4
-	n := 10
+	n := 7
 	round := DKGDelayRound
 	reset := uint64(0)
 	cfgChains := s.runDKG(k, n, round, reset)
@@ -320,7 +320,7 @@ func (s *ConfigurationChainTestSuite) TestConfigurationChain() {
 
 func (s *ConfigurationChainTestSuite) TestDKGMasterPublicKeyDelayAdd() {
 	k := 4
-	n := 10
+	n := 7
 	round := DKGDelayRound
 	reset := uint64(0)
 	lambdaDKG := 1000 * time.Millisecond
@@ -387,7 +387,7 @@ func (s *ConfigurationChainTestSuite) TestDKGMasterPublicKeyDelayAdd() {
 
 func (s *ConfigurationChainTestSuite) TestDKGComplaintDelayAdd() {
 	k := 4
-	n := 10
+	n := 7
 	round := DKGDelayRound
 	reset := uint64(0)
 	lambdaDKG := 1000 * time.Millisecond
diff --git a/core/consensus.go b/core/consensus.go
index 6d0f683..2246bf1 100644
--- a/core/consensus.go
+++ b/core/consensus.go
@@ -849,17 +849,21 @@ func (con *Consensus) prepare(initBlock *types.Block) (err error) {
 					"reset", e.Reset)
 				return false
 			}
-			if _, err := typesDKG.NewGroupPublicKey(
+			gpk, err := typesDKG.NewGroupPublicKey(
 				nextRound,
 				con.gov.DKGMasterPublicKeys(nextRound),
 				con.gov.DKGComplaints(nextRound),
-				utils.GetDKGThreshold(nextConfig)); err != nil {
+				utils.GetDKGThreshold(nextConfig))
+			if err != nil {
 				con.logger.Error("Next DKG failed to prepare, reset it",
 					"round", e.Round,
 					"reset", e.Reset,
 					"error", err)
 				return false
 			}
+			if len(gpk.QualifyNodeIDs) < utils.GetDKGValidThreshold(nextConfig) {
+				return false
+			}
 			return true
 		}
 		con.event.RegisterHeight(e.NextDKGResetHeight(), func(uint64) {
diff --git a/core/utils/utils.go b/core/utils/utils.go
index fcdf422..9a4ae92 100644
--- a/core/utils/utils.go
+++ b/core/utils/utils.go
@@ -139,6 +139,11 @@ func GetDKGThreshold(config *types.Config) int {
 	return int(config.NotarySetSize*2/3) + 1
 }
 
+// GetDKGValidThreshold return threshold for DKG set to considered valid.
+func GetDKGValidThreshold(config *types.Config) int {
+	return int(config.NotarySetSize * 5 / 6)
+}
+
 // GetNextRoundValidationHeight returns the block height to check if the next
 // round is ready.
 func GetNextRoundValidationHeight(begin, length uint64) uint64 {