core: polish dkg for recovery (#443)

* core: Add an error to NewGroupPublicKey

* core: Add Delete to TSigVerifierCache

* remove duplicated check

3 files changed, 16 insertions, 5 deletions

diff --git a/core/configuration-chain.go b/core/configuration-chain.go
index bec47f4..ad4d7e6 100644
--- a/core/configuration-chain.go
+++ b/core/configuration-chain.go
@@ -308,11 +308,6 @@ func (cc *configurationChain) recoverDKGInfo(round uint64) error {
 	if err != nil {
 		return err
 	}
-	// Restore DKG share secret, this segment of code is copied from
-	// dkgProtocol.recoverShareSecret.
-	if len(gpk.qualifyIDs) < threshold {
-		return ErrNotReachThreshold
-	}
 	// Check if we have private shares in DB.
 	prvKey, err := cc.db.GetDKGPrivateKey(round)
 	if err != nil {
diff --git a/core/dkg-tsig-protocol.go b/core/dkg-tsig-protocol.go
index 73b8abf..2028154 100644
--- a/core/dkg-tsig-protocol.go
+++ b/core/dkg-tsig-protocol.go
@@ -400,6 +400,9 @@ func NewDKGGroupPublicKey(
 		}
 	}
 	qualifyIDs := make(dkg.IDs, 0, len(mpks)-len(disqualifyIDs))
+	if cap(qualifyIDs) < threshold {
+		return nil, ErrNotReachThreshold
+	}
 	qualifyNodeIDs := make(map[types.NodeID]struct{})
 	mpkMap := make(map[dkg.ID]*typesDKG.MasterPublicKey, cap(qualifyIDs))
 	idMap := make(map[types.NodeID]dkg.ID)
@@ -515,6 +518,13 @@ func (tc *TSigVerifierCache) Update(round uint64) (bool, error) {
 	return true, nil
 }
 
+// Delete the cache of given round.
+func (tc *TSigVerifierCache) Delete(round uint64) {
+	tc.lock.Lock()
+	defer tc.lock.Unlock()
+	delete(tc.verifier, round)
+}
+
 // Get the TSigVerifier of round and returns if it exists.
 func (tc *TSigVerifierCache) Get(round uint64) (TSigVerifier, bool) {
 	tc.lock.RLock()
diff --git a/core/dkg-tsig-protocol_test.go b/core/dkg-tsig-protocol_test.go
index 54118f6..4086267 100644
--- a/core/dkg-tsig-protocol_test.go
+++ b/core/dkg-tsig-protocol_test.go
@@ -780,6 +780,11 @@ func (s *DKGTSIGProtocolTestSuite) TestTSigVerifierCache() {
 	ok, err := cache.Update(uint64(1))
 	s.Require().Equal(ErrRoundAlreadyPurged, err)
 
+	cache.Delete(uint64(5))
+	s.Len(cache.verifier, 2)
+	_, exist := cache.Get(uint64(5))
+	s.False(exist)
+
 	cache = NewTSigVerifierCache(gov, 1)
 	ok, err = cache.Update(uint64(3))
 	s.Require().NoError(err)
@@ -790,6 +795,7 @@ func (s *DKGTSIGProtocolTestSuite) TestTSigVerifierCache() {
 	s.Require().NoError(err)
 	s.Require().True(ok)
 	s.Equal(uint64(5), cache.minRound)
+
 }
 
 func TestDKGTSIGProtocol(t *testing.T) {