core: Add a `MPKReady` so `MasterPublicKey` cannot be added afterwards (#375)

* Add type DKGReady

* Add DKGReady to interface and state

* DKG will wait for MPK to be ready before running

* Modify test

* Check if self's MPK is registered

* Add test for delay add MPK

* Rename Ready to MPKReady

2 files changed, 52 insertions, 0 deletions

diff --git a/core/types/dkg/dkg.go b/core/types/dkg/dkg.go
index cecc4f1..f021d1b 100644
--- a/core/types/dkg/dkg.go
+++ b/core/types/dkg/dkg.go
@@ -167,6 +167,27 @@ type PartialSignature struct {
 	Signature        crypto.Signature           `json:"signature"`
 }
 
+// MPKReady describe a dig ready message in DKG protocol.
+type MPKReady struct {
+	ProposerID types.NodeID     `json:"proposer_id"`
+	Round      uint64           `json:"round"`
+	Signature  crypto.Signature `json:"signature"`
+}
+
+func (ready *MPKReady) String() string {
+	return fmt.Sprintf("DKGMPKReady{RP:%s Round:%d}",
+		ready.ProposerID.String()[:6],
+		ready.Round)
+}
+
+// Equal check equality of two MPKReady instances.
+func (ready *MPKReady) Equal(other *MPKReady) bool {
+	return ready.ProposerID.Equal(other.ProposerID) &&
+		ready.Round == other.Round &&
+		ready.Signature.Type == other.Signature.Type &&
+		bytes.Compare(ready.Signature.Signature, other.Signature.Signature) == 0
+}
+
 // Finalize describe a dig finalize message in DKG protocol.
 type Finalize struct {
 	ProposerID types.NodeID     `json:"proposer_id"`
diff --git a/core/types/dkg/dkg_test.go b/core/types/dkg/dkg_test.go
index ea46621..4eb17ac 100644
--- a/core/types/dkg/dkg_test.go
+++ b/core/types/dkg/dkg_test.go
@@ -212,6 +212,37 @@ func (s *DKGTestSuite) TestComplaintEquality() {
 	req.True(comp1.Equal(comp2))
 }
 
+func (s *DKGTestSuite) TestMPKReadyEquality() {
+	var req = s.Require()
+	ready1 := &MPKReady{
+		ProposerID: types.NodeID{Hash: common.NewRandomHash()},
+		Round:      1,
+		Signature: crypto.Signature{
+			Signature: s.genRandomBytes(),
+		},
+	}
+	// Make a copy
+	ready2 := &MPKReady{}
+	s.clone(ready1, ready2)
+	req.True(ready1.Equal(ready2))
+	// Change proposer ID.
+	ready2.ProposerID = types.NodeID{Hash: common.NewRandomHash()}
+	req.False(ready1.Equal(ready2))
+	ready2.ProposerID = ready1.ProposerID
+	// Change round.
+	ready2.Round = ready1.Round + 1
+	req.False(ready1.Equal(ready2))
+	ready2.Round = ready1.Round
+	// Change signature.
+	ready2.Signature = crypto.Signature{
+		Signature: s.genRandomBytes(),
+	}
+	req.False(ready1.Equal(ready2))
+	ready2.Signature = ready1.Signature
+	// After changing every field back, they should be equal.
+	req.True(ready1.Equal(ready2))
+}
+
 func (s *DKGTestSuite) TestFinalizeEquality() {
 	var req = s.Require()
 	final1 := &Finalize{