core: replace reliable-broadcast with shard (#159)

16 files changed, 264 insertions, 1458 deletions

diff --git a/core/blocklattice.go b/core/blocklattice.go
index 3fa0736..59adaf2 100644
--- a/core/blocklattice.go
+++ b/core/blocklattice.go
@@ -19,6 +19,7 @@ package core
 
 import (
 	"fmt"
+	"time"
 
 	"github.com/dexon-foundation/dexon-consensus-core/common"
 	"github.com/dexon-foundation/dexon-consensus-core/core/types"
@@ -30,6 +31,15 @@ var (
 	ErrInvalidParentChain      = fmt.Errorf("invalid parent chain")
 	ErrDuplicatedAckOnOneChain = fmt.Errorf("duplicated ack on one chain")
 	ErrChainStatusCorrupt      = fmt.Errorf("chain status corrupt")
+	ErrInvalidChainID          = fmt.Errorf("invalid chain id")
+	ErrInvalidProposerID       = fmt.Errorf("invalid proposer id")
+	ErrInvalidTimestamp        = fmt.Errorf("invalid timestamp")
+	ErrForkBlock               = fmt.Errorf("fork block")
+	ErrNotAckParent            = fmt.Errorf("not ack parent")
+	ErrDoubleAck               = fmt.Errorf("double ack")
+	ErrInvalidBlockHeight      = fmt.Errorf("invalid block height")
+	ErrAlreadyInLattice        = fmt.Errorf("block already in lattice")
+	ErrIncorrectBlockTime      = fmt.Errorf("block timestampe is incorrect")
 )
 
 // blockLattice is a module for storing blocklattice.
@@ -40,8 +50,10 @@ type blockLattice struct {
 	// blockByHash stores blocks, indexed by block hash.
 	blockByHash map[common.Hash]*types.Block
 
-	// shardID caches which shard I belongs to.
-	shardID uint32
+	// Block interval specifies reasonable time difference between
+	// parent/child blocks.
+	minBlockTimeInterval time.Duration
+	maxBlockTimeInterval time.Duration
 }
 
 type chainStatus struct {
@@ -132,7 +144,7 @@ func (s *chainStatus) purge() (purged common.Hashes) {
 }
 
 // nextPosition returns a valid position for new block in this chain.
-func (s *chainStatus) nextPosition(shardID uint32) types.Position {
+func (s *chainStatus) nextPosition() types.Position {
 	return types.Position{
 		ChainID: s.ID,
 		Height:  s.minHeight + uint64(len(s.blocks)),
@@ -140,11 +152,15 @@ func (s *chainStatus) nextPosition(shardID uint32) types.Position {
 }
 
 // newBlockLattice creates a new blockLattice struct.
-func newBlockLattice(shardID, chainNum uint32) (bl *blockLattice) {
+func newBlockLattice(
+	chainNum uint32,
+	minBlockTimeInterval time.Duration,
+	maxBlockTimeInterval time.Duration) (bl *blockLattice) {
 	bl = &blockLattice{
-		shardID:     shardID,
-		chains:      make([]*chainStatus, chainNum),
-		blockByHash: make(map[common.Hash]*types.Block),
+		chains:               make([]*chainStatus, chainNum),
+		blockByHash:          make(map[common.Hash]*types.Block),
+		minBlockTimeInterval: minBlockTimeInterval,
+		maxBlockTimeInterval: maxBlockTimeInterval,
 	}
 	for i := range bl.chains {
 		bl.chains[i] = &chainStatus{
@@ -213,6 +229,12 @@ func (bl *blockLattice) sanityCheck(b *types.Block) error {
 		if !b.Timestamp.After(bParent.Timestamp) {
 			return ErrInvalidTimestamp
 		}
+		// Check if its timestamp is in expected range.
+		if b.Timestamp.Before(bParent.Timestamp.Add(bl.minBlockTimeInterval)) ||
+			b.Timestamp.After(bParent.Timestamp.Add(bl.maxBlockTimeInterval)) {
+
+			return ErrIncorrectBlockTime
+		}
 	}
 	return nil
 }
@@ -248,6 +270,7 @@ func (bl *blockLattice) addBlock(
 		bAck    *types.Block
 		updated bool
 	)
+	// TODO(mission): sanity check twice, might hurt performance.
 	// If a block does not pass sanity check, report error.
 	if err = bl.sanityCheck(block); err != nil {
 		return
@@ -355,5 +378,5 @@ func (bl *blockLattice) prepareBlock(block *types.Block) {
 // TODO(mission): make more abstraction for this method.
 // nextHeight returns the next height for the chain.
 func (bl *blockLattice) nextPosition(chainID uint32) types.Position {
-	return bl.chains[chainID].nextPosition(bl.shardID)
+	return bl.chains[chainID].nextPosition()
 }
diff --git a/core/blocklattice_test.go b/core/blocklattice_test.go
index 76e5129..72cde7d 100644
--- a/core/blocklattice_test.go
+++ b/core/blocklattice_test.go
@@ -78,7 +78,7 @@ func (s *BlockLatticeTest) genTestCase1() (bl *blockLattice) {
 		err       error
 	)
 
-	bl = newBlockLattice(0, chainNum)
+	bl = newBlockLattice(chainNum, 2*time.Nanosecond, 1000*time.Second)
 	// Add genesis blocks.
 	for i := uint32(0); i < chainNum; i++ {
 		b = s.prepareGenesisBlock(i)
@@ -314,6 +314,30 @@ func (s *BlockLatticeTest) TestSanityCheck() {
 	req.NotNil(err)
 	req.Equal(err.Error(), ErrDuplicatedAckOnOneChain.Error())
 
+	// Add block 3-1 which acks 3-0, and violet reasonable block time interval.
+	h = bl.chains[2].getBlockByHeight(0).Hash
+	b = &types.Block{
+		ParentHash: h,
+		Hash:       common.NewRandomHash(),
+		Timestamp:  time.Now().UTC().Add(bl.maxBlockTimeInterval),
+		Position: types.Position{
+			ChainID: 2,
+			Height:  1,
+		},
+		Acks: common.NewSortedHashes(common.Hashes{h}),
+	}
+	s.hashBlock(b)
+	err = bl.sanityCheck(b)
+	req.NotNil(err)
+	req.Equal(err, ErrIncorrectBlockTime)
+	// Violet minimum block time interval.
+	b.Timestamp =
+		bl.chains[2].getBlockByHeight(0).Timestamp.Add(1 * time.Nanosecond)
+	s.hashBlock(b)
+	err = bl.sanityCheck(b)
+	req.NotNil(err)
+	req.Equal(err, ErrIncorrectBlockTime)
+
 	// Normal block.
 	h = bl.chains[1].getBlockByHeight(0).Hash
 	b = &types.Block{
@@ -361,7 +385,7 @@ func (s *BlockLatticeTest) TestAreAllAcksInLattice() {
 func (s *BlockLatticeTest) TestRandomIntensiveAcking() {
 	var (
 		chainNum  uint32 = 19
-		bl               = newBlockLattice(0, chainNum)
+		bl               = newBlockLattice(chainNum, 0, 1000*time.Second)
 		req              = s.Require()
 		delivered []*types.Block
 		extracted []*types.Block
@@ -424,7 +448,7 @@ func (s *BlockLatticeTest) TestRandomlyGeneratedBlocks() {
 	revealedHashesAsString := map[string]struct{}{}
 	deliveredHashesAsString := map[string]struct{}{}
 	for i := 0; i < repeat; i++ {
-		bl := newBlockLattice(0, chainNum)
+		bl := newBlockLattice(chainNum, 0, 1000*time.Second)
 		deliveredHashes := common.Hashes{}
 		revealedHashes := common.Hashes{}
 		revealer.Reset()
@@ -502,7 +526,7 @@ func (s *BlockLatticeTest) TestPrepareBlock() {
 	var (
 		chainNum    uint32 = 4
 		req                = s.Require()
-		bl                 = newBlockLattice(0, chainNum)
+		bl                 = newBlockLattice(chainNum, 0, 3000*time.Second)
 		minInterval        = 50 * time.Millisecond
 		delivered   []*types.Block
 		err         error
@@ -627,6 +651,16 @@ func (s *BlockLatticeTest) TestPurge() {
 	s.Equal(chain.blocks[1].Hash, b02.Hash)
 }
 
+func (s *BlockLatticeTest) TestNextPosition() {
+	// Test 'NextPosition' method when lattice is ready.
+	bl := s.genTestCase1()
+	s.Equal(bl.nextPosition(0), types.Position{ChainID: 0, Height: 4})
+
+	// Test 'NextPosition' method when lattice is empty.
+	bl = newBlockLattice(4, 0, 1000*time.Second)
+	s.Equal(bl.nextPosition(0), types.Position{ChainID: 0, Height: 0})
+}
+
 func TestBlockLattice(t *testing.T) {
 	suite.Run(t, new(BlockLatticeTest))
 }
diff --git a/core/consensus.go b/core/consensus.go
index a1642df..e7b5ec7 100644
--- a/core/consensus.go
+++ b/core/consensus.go
@@ -30,16 +30,6 @@ import (
 	"github.com/dexon-foundation/dexon-consensus-core/core/types"
 )
 
-// ErrMissingBlockInfo would be reported if some information is missing when
-// calling PrepareBlock. It implements error interface.
-type ErrMissingBlockInfo struct {
-	MissingField string
-}
-
-func (e *ErrMissingBlockInfo) Error() string {
-	return "missing " + e.MissingField + " in block"
-}
-
 // Errors for consensus core.
 var (
 	ErrProposerNotInNodeSet = fmt.Errorf(
@@ -54,10 +44,6 @@ var (
 		"unknown block is proposed")
 	ErrUnknownBlockConfirmed = fmt.Errorf(
 		"unknown block is confirmed")
-	ErrIncorrectBlockPosition = fmt.Errorf(
-		"position of block is incorrect")
-	ErrIncorrectBlockTime = fmt.Errorf(
-		"block timestampe is incorrect")
 )
 
 // consensusBAReceiver implements agreementReceiver.
@@ -182,11 +168,9 @@ type Consensus struct {
 	dkgReady   *sync.Cond
 	cfgModule  *configurationChain
 
-	// Dexon consensus modules.
-	rbModule *reliableBroadcast
-	toModule *totalOrdering
-	ctModule *consensusTimestamp
-	ccModule *compactionChain
+	// Dexon consensus v1's modules.
+	shardModule *Shard
+	ccModule    *compactionChain
 
 	// Interfaces.
 	db        blockdb.BlockDatabase
@@ -212,33 +196,29 @@ func NewConsensus(
 
 	// TODO(w): load latest blockHeight from DB, and use config at that height.
 	var round uint64
-	config := gov.GetConfiguration(round)
+	config := gov.Configuration(round)
 	// TODO(w): notarySet is different for each chain, need to write a
 	// GetNotarySetForChain(nodeSet, shardID, chainID, crs) function to get the
 	// correct notary set for a given chain.
 	nodeSetCache := NewNodeSetCache(gov)
-	crs := gov.GetCRS(round)
+	crs := gov.CRS(round)
 	// Setup acking by information returned from Governace.
 	nodes, err := nodeSetCache.GetNodeSet(0)
 	if err != nil {
 		panic(err)
 	}
-	rb := newReliableBroadcast()
-	rb.setChainNum(config.NumChains)
-	for nID := range nodes.IDs {
-		rb.addNode(nID)
-	}
 	// Setup context.
 	ctx, ctxCancel := context.WithCancel(context.Background())
-
-	// Setup sequencer by information returned from Governace.
-	to := newTotalOrdering(
-		uint64(config.K),
-		uint64(float32(len(nodes.IDs)-1)*config.PhiRatio+1),
-		config.NumChains)
-
-	ID := types.NewNodeID(prv.PublicKey())
+	// Setup auth module.
 	authModule := NewAuthenticator(prv)
+	// Check if the application implement Debug interface.
+	debugApp, _ := app.(Debug)
+	// Setup nonblocking module.
+	nbModule := newNonBlocking(app, debugApp)
+	// Init shard.
+	shardModule := NewShard(config, authModule, nbModule, nbModule, db)
+	// Init configuration chain.
+	ID := types.NewNodeID(prv.PublicKey())
 	cfgModule := newConfigurationChain(
 		ID,
 		&consensusDKGReceiver{
@@ -252,17 +232,13 @@ func NewConsensus(
 	// Register DKG for the initial round. This is a temporary function call for
 	// simulation.
 	cfgModule.registerDKG(0, config.NumDKGSet/3)
-
-	// Check if the application implement Debug interface.
-	debug, _ := app.(Debug)
+	// Construct Consensus instance.
 	con := &Consensus{
 		ID:            ID,
 		currentConfig: config,
-		rbModule:      rb,
-		toModule:      to,
-		ctModule:      newConsensusTimestamp(),
 		ccModule:      newCompactionChain(db),
-		nbModule:      newNonBlocking(app, debug),
+		shardModule:   shardModule,
+		nbModule:      nbModule,
 		gov:           gov,
 		db:            db,
 		network:       network,
@@ -356,14 +332,10 @@ BALoop:
 				if err != nil {
 					panic(err)
 				}
-				nIDs = nodes.GetSubSet(con.gov.GetConfiguration(con.round).NumNotarySet,
-					types.NewNotarySetTarget(con.gov.GetCRS(con.round), chainID))
-			}
-			aID := types.Position{
-				ChainID: chainID,
-				Height:  con.rbModule.nextHeight(chainID),
+				nIDs = nodes.GetSubSet(con.gov.Configuration(con.round).NumNotarySet,
+					types.NewNotarySetTarget(con.gov.CRS(con.round), chainID))
 			}
-			agreement.restart(nIDs, aID)
+			agreement.restart(nIDs, con.shardModule.NextPosition(chainID))
 		default:
 		}
 		err := agreement.nextState()
@@ -406,7 +378,7 @@ func (con *Consensus) runDKGTSIG() {
 		}
 		hash := HashConfigurationBlock(
 			nodes.IDs,
-			con.gov.GetConfiguration(round),
+			con.gov.Configuration(round),
 			common.Hash{},
 			con.cfgModule.prevHash)
 		psig, err := con.cfgModule.preparePartialSignature(
@@ -438,7 +410,7 @@ func (con *Consensus) runCRS() {
 		<-ticker.Tick()
 		// Start running next round CRS.
 		psig, err := con.cfgModule.preparePartialSignature(
-			con.round, con.gov.GetCRS(con.round), types.TSigCRS)
+			con.round, con.gov.CRS(con.round), types.TSigCRS)
 		if err != nil {
 			log.Println(err)
 		} else if err = con.authModule.SignDKGPartialSignature(psig); err != nil {
@@ -447,7 +419,7 @@ func (con *Consensus) runCRS() {
 			log.Println(err)
 		} else {
 			con.network.BroadcastDKGPartialSignature(psig)
-			crs, err := con.cfgModule.runCRSTSig(con.round, con.gov.GetCRS(con.round))
+			crs, err := con.cfgModule.runCRSTSig(con.round, con.gov.CRS(con.round))
 			if err != nil {
 				log.Println(err)
 			} else {
@@ -458,7 +430,7 @@ func (con *Consensus) runCRS() {
 		<-ticker.Tick()
 		// Change round.
 		con.round++
-		con.currentConfig = con.gov.GetConfiguration(con.round)
+		con.currentConfig = con.gov.Configuration(con.round)
 		func() {
 			con.dkgReady.L.Lock()
 			defer con.dkgReady.L.Unlock()
@@ -506,23 +478,14 @@ func (con *Consensus) processMsg(msgChan <-chan interface{}) {
 
 func (con *Consensus) proposeBlock(chainID uint32) *types.Block {
 	block := &types.Block{
-		ProposerID: con.ID,
 		Position: types.Position{
 			ChainID: chainID,
-			Height:  con.rbModule.nextHeight(chainID),
 		},
 	}
 	if err := con.prepareBlock(block, time.Now().UTC()); err != nil {
 		log.Println(err)
 		return nil
 	}
-	// TODO(mission): decide CRS by block's round, which could be determined by
-	//                block's info (ex. position, timestamp).
-	if err := con.authModule.SignCRS(
-		block, con.gov.GetCRS(0)); err != nil {
-		log.Println(err)
-		return nil
-	}
 	return block
 }
 
@@ -533,43 +496,12 @@ func (con *Consensus) ProcessVote(vote *types.Vote) (err error) {
 	return err
 }
 
-// sanityCheck checks if the block is a valid block
-func (con *Consensus) sanityCheck(b *types.Block) (err error) {
-	// Check block.Position.
-	if b.Position.ChainID >= con.rbModule.chainNum() {
-		return ErrIncorrectBlockPosition
-	}
-	// Check the timestamp of block.
-	if !b.IsGenesis() {
-		chainTime := con.rbModule.chainTime(b.Position.ChainID)
-		if b.Timestamp.Before(chainTime.Add(con.currentConfig.MinBlockInterval)) ||
-			b.Timestamp.After(chainTime.Add(con.currentConfig.MaxBlockInterval)) {
-			return ErrIncorrectBlockTime
-		}
-	}
-	// Check the hash of block.
-	hash, err := hashBlock(b)
-	if err != nil || hash != b.Hash {
-		return ErrIncorrectHash
-	}
-
-	// Check the signer.
-	pubKey, err := crypto.SigToPub(b.Hash, b.Signature)
-	if err != nil {
-		return err
-	}
-	if !b.ProposerID.Equal(crypto.Keccak256Hash(pubKey.Bytes())) {
-		return ErrIncorrectSignature
-	}
-	return nil
-}
-
 // preProcessBlock performs Byzantine Agreement on the block.
 func (con *Consensus) preProcessBlock(b *types.Block) (err error) {
-	if err := con.sanityCheck(b); err != nil {
-		return err
+	if err = con.shardModule.SanityCheck(b); err != nil {
+		return
 	}
-	if err := con.baModules[b.Position.ChainID].processBlock(b); err != nil {
+	if err = con.baModules[b.Position.ChainID].processBlock(b); err != nil {
 		return err
 	}
 	return
@@ -577,73 +509,30 @@ func (con *Consensus) preProcessBlock(b *types.Block) (err error) {
 
 // processBlock is the entry point to submit one block to a Consensus instance.
 func (con *Consensus) processBlock(block *types.Block) (err error) {
-	if err := con.sanityCheck(block); err != nil {
-		return err
+	verifiedBlocks, deliveredBlocks, err := con.shardModule.ProcessBlock(block)
+	if err != nil {
+		return
 	}
-	var (
-		deliveredBlocks []*types.Block
-		earlyDelivered  bool
-	)
-	// To avoid application layer modify the content of block during
-	// processing, we should always operate based on the cloned one.
-	b := block.Clone()
-
-	con.lock.Lock()
-	defer con.lock.Unlock()
-	// Perform reliable broadcast checking.
-	if err = con.rbModule.processBlock(b); err != nil {
-		return err
+	// Pass verified blocks (pass sanity check) back to BA module.
+	for _, b := range verifiedBlocks {
+		if err :=
+			con.baModules[b.Position.ChainID].processBlock(b); err != nil {
+			return err
+		}
 	}
-	con.nbModule.BlockConfirmed(block.Hash)
-	for _, b := range con.rbModule.extractBlocks() {
-		// Notify application layer that some block is strongly acked.
-		con.nbModule.StronglyAcked(b.Hash)
-		// Perform total ordering.
-		deliveredBlocks, earlyDelivered, err = con.toModule.processBlock(b)
-		if err != nil {
+	// Pass delivered blocks to compaction chain.
+	for _, b := range deliveredBlocks {
+		if err = con.ccModule.processBlock(b); err != nil {
 			return
 		}
-		if len(deliveredBlocks) == 0 {
-			continue
-		}
-		for _, b := range deliveredBlocks {
-			if err = con.db.Put(*b); err != nil {
-				return
-			}
-		}
-		// TODO(mission): handle membership events here.
-		hashes := make(common.Hashes, len(deliveredBlocks))
-		for idx := range deliveredBlocks {
-			hashes[idx] = deliveredBlocks[idx].Hash
-		}
-		con.nbModule.TotalOrderingDelivered(hashes, earlyDelivered)
-		// Perform timestamp generation.
-		err = con.ctModule.processBlocks(deliveredBlocks)
-		if err != nil {
+		if err = con.db.Update(*b); err != nil {
 			return
 		}
-		for _, b := range deliveredBlocks {
-			if err = con.ccModule.processBlock(b); err != nil {
-				return
-			}
-			if err = con.db.Update(*b); err != nil {
-				return
-			}
-			con.nbModule.BlockDelivered(*b)
-			// TODO(mission): Find a way to safely recycle the block.
-			//                We should deliver block directly to
-			//                nonBlocking and let them recycle the
-			//                block.
-		}
-	}
-	return
-}
-
-func (con *Consensus) checkPrepareBlock(
-	b *types.Block, proposeTime time.Time) (err error) {
-	if (b.ProposerID == types.NodeID{}) {
-		err = &ErrMissingBlockInfo{MissingField: "ProposerID"}
-		return
+		con.nbModule.BlockDelivered(*b)
+		// TODO(mission): Find a way to safely recycle the block.
+		//                We should deliver block directly to
+		//                nonBlocking and let them recycle the
+		//                block.
 	}
 	return
 }
@@ -651,16 +540,12 @@ func (con *Consensus) checkPrepareBlock(
 // PrepareBlock would setup header fields of block based on its ProposerID.
 func (con *Consensus) prepareBlock(b *types.Block,
 	proposeTime time.Time) (err error) {
-	if err = con.checkPrepareBlock(b, proposeTime); err != nil {
+	if err = con.shardModule.PrepareBlock(b, proposeTime); err != nil {
 		return
 	}
-	con.lock.RLock()
-	defer con.lock.RUnlock()
-
-	con.rbModule.prepareBlock(b)
-	b.Timestamp = proposeTime
-	b.Payload, b.Witness.Data = con.nbModule.PrepareBlock(b.Position)
-	if err = con.authModule.SignBlock(b); err != nil {
+	// TODO(mission): decide CRS by block's round, which could be determined by
+	//                block's info (ex. position, timestamp).
+	if err = con.authModule.SignCRS(b, con.gov.CRS(0)); err != nil {
 		return
 	}
 	return
@@ -669,18 +554,12 @@ func (con *Consensus) prepareBlock(b *types.Block,
 // PrepareGenesisBlock would setup header fields for genesis block.
 func (con *Consensus) PrepareGenesisBlock(b *types.Block,
 	proposeTime time.Time) (err error) {
-	if err = con.checkPrepareBlock(b, proposeTime); err != nil {
+	if err = con.prepareBlock(b, proposeTime); err != nil {
 		return
 	}
 	if len(b.Payload) != 0 {
 		err = ErrGenesisBlockNotEmpty
 		return
 	}
-	b.Position.Height = 0
-	b.ParentHash = common.Hash{}
-	b.Timestamp = proposeTime
-	if err = con.authModule.SignBlock(b); err != nil {
-		return
-	}
 	return
 }
diff --git a/core/consensus_test.go b/core/consensus_test.go
index 583a2e5..71163e7 100644
--- a/core/consensus_test.go
+++ b/core/consensus_test.go
@@ -67,18 +67,16 @@ type ConsensusTestSuite struct {
 }
 
 func (s *ConsensusTestSuite) prepareGenesisBlock(
-	proposerID types.NodeID,
 	chainID uint32,
 	con *Consensus) *types.Block {
 
 	block := &types.Block{
-		ProposerID: proposerID,
 		Position: types.Position{
 			ChainID: chainID,
 		},
 	}
 	err := con.PrepareGenesisBlock(block, time.Now().UTC())
-	s.Require().Nil(err)
+	s.Require().NoError(err)
 	return block
 }
 
@@ -103,12 +101,14 @@ func (s *ConsensusTestSuite) TestSimpleDeliverBlock() {
 	// o o o o <- genesis blocks
 	// 0 1 2 3 <- index of node ID
 	//
-	// This test case only works for Total Ordering with K=0.
+	// - This test case only works for Total Ordering with K=0.
+	// - Byzantine Agreement layer is not taken into consideration, every
+	//   block is passed to shard module directly.
 	var (
 		gov, err    = test.NewGovernance(4, time.Second)
-		minInterval = gov.GetConfiguration(0).MinBlockInterval
+		minInterval = gov.Configuration(0).MinBlockInterval
 		req         = s.Require()
-		prvKeys     = gov.GetPrivateKeys()
+		prvKeys     = gov.PrivateKeys()
 		nodes       []types.NodeID
 	)
 	s.Require().Nil(err)
@@ -134,24 +134,22 @@ func (s *ConsensusTestSuite) TestSimpleDeliverBlock() {
 		}
 	}
 	// Genesis blocks
-	b00 := s.prepareGenesisBlock(nodes[0], 0, objs[nodes[0]].con)
-	b10 := s.prepareGenesisBlock(nodes[1], 1, objs[nodes[1]].con)
-	b20 := s.prepareGenesisBlock(nodes[2], 2, objs[nodes[2]].con)
-	b30 := s.prepareGenesisBlock(nodes[3], 3, objs[nodes[3]].con)
+	b00 := s.prepareGenesisBlock(0, objs[nodes[0]].con)
+	b10 := s.prepareGenesisBlock(1, objs[nodes[1]].con)
+	b20 := s.prepareGenesisBlock(2, objs[nodes[2]].con)
+	b30 := s.prepareGenesisBlock(3, objs[nodes[3]].con)
 	broadcast(b00)
 	broadcast(b10)
 	broadcast(b20)
 	broadcast(b30)
 	// Setup b11.
 	b11 := &types.Block{
-		ProposerID: nodes[1],
 		Position: types.Position{
 			ChainID: 1,
 		},
 	}
-	b11.Hash, err = hashBlock(b11)
-	s.Require().Nil(err)
-	req.Nil(objs[nodes[1]].con.prepareBlock(b11, b10.Timestamp.Add(minInterval)))
+	req.NoError(
+		objs[nodes[1]].con.prepareBlock(b11, b10.Timestamp.Add(minInterval)))
 	req.Len(b11.Acks, 4)
 	req.Contains(b11.Acks, b00.Hash)
 	req.Contains(b11.Acks, b10.Hash)
@@ -160,37 +158,43 @@ func (s *ConsensusTestSuite) TestSimpleDeliverBlock() {
 	broadcast(b11)
 	// Setup b01.
 	b01 := &types.Block{
-		ProposerID: nodes[0],
 		Position: types.Position{
 			ChainID: 0,
 		},
-		Hash: common.NewRandomHash(),
 	}
-	req.Nil(objs[nodes[0]].con.prepareBlock(b01, b00.Timestamp.Add(minInterval)))
+	req.NoError(
+		objs[nodes[0]].con.prepareBlock(b01, b00.Timestamp.Add(minInterval)))
 	req.Len(b01.Acks, 4)
+	req.Contains(b01.Acks, b00.Hash)
 	req.Contains(b01.Acks, b11.Hash)
+	req.Contains(b01.Acks, b20.Hash)
+	req.Contains(b01.Acks, b30.Hash)
 	// Setup b21.
 	b21 := &types.Block{
-		ProposerID: nodes[2],
 		Position: types.Position{
 			ChainID: 2,
 		},
-		Hash: common.NewRandomHash(),
 	}
-	req.Nil(objs[nodes[2]].con.prepareBlock(b21, b20.Timestamp.Add(minInterval)))
+	req.NoError(
+		objs[nodes[2]].con.prepareBlock(b21, b20.Timestamp.Add(minInterval)))
 	req.Len(b21.Acks, 4)
+	req.Contains(b21.Acks, b00.Hash)
 	req.Contains(b21.Acks, b11.Hash)
+	req.Contains(b21.Acks, b20.Hash)
+	req.Contains(b21.Acks, b30.Hash)
 	// Setup b31.
 	b31 := &types.Block{
-		ProposerID: nodes[3],
 		Position: types.Position{
 			ChainID: 3,
 		},
-		Hash: common.NewRandomHash(),
 	}
-	req.Nil(objs[nodes[3]].con.prepareBlock(b31, b30.Timestamp.Add(minInterval)))
+	req.NoError(
+		objs[nodes[3]].con.prepareBlock(b31, b30.Timestamp.Add(minInterval)))
 	req.Len(b31.Acks, 4)
+	req.Contains(b31.Acks, b00.Hash)
 	req.Contains(b31.Acks, b11.Hash)
+	req.Contains(b31.Acks, b20.Hash)
+	req.Contains(b31.Acks, b30.Hash)
 	// Broadcast other height=1 blocks.
 	broadcast(b01)
 	broadcast(b21)
@@ -198,26 +202,24 @@ func (s *ConsensusTestSuite) TestSimpleDeliverBlock() {
 	// Setup height=2 blocks.
 	// Setup b02.
 	b02 := &types.Block{
-		ProposerID: nodes[0],
 		Position: types.Position{
 			ChainID: 0,
 		},
-		Hash: common.NewRandomHash(),
 	}
-	req.Nil(objs[nodes[0]].con.prepareBlock(b02, b01.Timestamp.Add(minInterval)))
+	req.NoError(
+		objs[nodes[0]].con.prepareBlock(b02, b01.Timestamp.Add(minInterval)))
 	req.Len(b02.Acks, 3)
 	req.Contains(b02.Acks, b01.Hash)
 	req.Contains(b02.Acks, b21.Hash)
 	req.Contains(b02.Acks, b31.Hash)
 	// Setup b12.
 	b12 := &types.Block{
-		ProposerID: nodes[1],
 		Position: types.Position{
 			ChainID: 1,
 		},
-		Hash: common.NewRandomHash(),
 	}
-	req.Nil(objs[nodes[1]].con.prepareBlock(b12, b11.Timestamp.Add(minInterval)))
+	req.NoError(
+		objs[nodes[1]].con.prepareBlock(b12, b11.Timestamp.Add(minInterval)))
 	req.Len(b12.Acks, 4)
 	req.Contains(b12.Acks, b01.Hash)
 	req.Contains(b12.Acks, b11.Hash)
@@ -225,26 +227,24 @@ func (s *ConsensusTestSuite) TestSimpleDeliverBlock() {
 	req.Contains(b12.Acks, b31.Hash)
 	// Setup b22.
 	b22 := &types.Block{
-		ProposerID: nodes[2],
 		Position: types.Position{
 			ChainID: 2,
 		},
-		Hash: common.NewRandomHash(),
 	}
-	req.Nil(objs[nodes[2]].con.prepareBlock(b22, b21.Timestamp.Add(minInterval)))
+	req.NoError(
+		objs[nodes[2]].con.prepareBlock(b22, b21.Timestamp.Add(minInterval)))
 	req.Len(b22.Acks, 3)
 	req.Contains(b22.Acks, b01.Hash)
 	req.Contains(b22.Acks, b21.Hash)
 	req.Contains(b22.Acks, b31.Hash)
 	// Setup b32.
 	b32 := &types.Block{
-		ProposerID: nodes[3],
 		Position: types.Position{
 			ChainID: 3,
 		},
-		Hash: common.NewRandomHash(),
 	}
-	req.Nil(objs[nodes[3]].con.prepareBlock(b32, b31.Timestamp.Add(minInterval)))
+	req.NoError(
+		objs[nodes[3]].con.prepareBlock(b32, b31.Timestamp.Add(minInterval)))
 	req.Len(b32.Acks, 3)
 	req.Contains(b32.Acks, b01.Hash)
 	req.Contains(b32.Acks, b21.Hash)
@@ -269,7 +269,7 @@ func (s *ConsensusTestSuite) TestSimpleDeliverBlock() {
 		// Genesis blocks are delivered by total ordering as a set.
 		delivered0 := common.Hashes{b00.Hash, b10.Hash, b20.Hash, b30.Hash}
 		sort.Sort(delivered0)
-		req.Len(app.TotalOrdered, 2)
+		req.Len(app.TotalOrdered, 4)
 		req.Equal(app.TotalOrdered[0].BlockHashes, delivered0)
 		req.False(app.TotalOrdered[0].Early)
 		// b11 is the sencond set delivered by total ordering.
@@ -277,6 +277,16 @@ func (s *ConsensusTestSuite) TestSimpleDeliverBlock() {
 		sort.Sort(delivered1)
 		req.Equal(app.TotalOrdered[1].BlockHashes, delivered1)
 		req.False(app.TotalOrdered[1].Early)
+		// b01, b21, b31 are the third set delivered by total ordering.
+		delivered2 := common.Hashes{b01.Hash, b21.Hash, b31.Hash}
+		sort.Sort(delivered2)
+		req.Equal(app.TotalOrdered[2].BlockHashes, delivered2)
+		req.False(app.TotalOrdered[2].Early)
+		// b02, b12, b22, b32 are the fourth set delivered by total ordering.
+		delivered3 := common.Hashes{b02.Hash, b12.Hash, b22.Hash, b32.Hash}
+		sort.Sort(delivered3)
+		req.Equal(app.TotalOrdered[3].BlockHashes, delivered3)
+		req.False(app.TotalOrdered[3].Early)
 		// Check generated timestamps.
 		req.Contains(app.Delivered, b00.Hash)
 		req.Contains(app.Delivered, b10.Hash)
@@ -292,7 +302,7 @@ func (s *ConsensusTestSuite) TestSimpleDeliverBlock() {
 		timestamps[2] = b20.Timestamp
 		timestamps[3] = b30.Timestamp
 		t, err := getMedianTime(timestamps)
-		req.Nil(err)
+		req.NoError(err)
 		req.Equal(t, app.Delivered[b11.Hash].ConsensusTime)
 	}
 	for _, obj := range objs {
@@ -313,7 +323,7 @@ func (s *ConsensusTestSuite) TestPrepareBlock() {
 		gov, err = test.NewGovernance(4, time.Second)
 		req      = s.Require()
 		nodes    []types.NodeID
-		prvKeys  = gov.GetPrivateKeys()
+		prvKeys  = gov.PrivateKeys()
 	)
 	s.Require().Nil(err)
 	// Setup core.Consensus and test.App.
@@ -324,10 +334,10 @@ func (s *ConsensusTestSuite) TestPrepareBlock() {
 		cons[nID] = con
 		nodes = append(nodes, nID)
 	}
-	b00 := s.prepareGenesisBlock(nodes[0], 0, cons[nodes[0]])
-	b10 := s.prepareGenesisBlock(nodes[1], 1, cons[nodes[1]])
-	b20 := s.prepareGenesisBlock(nodes[2], 2, cons[nodes[2]])
-	b30 := s.prepareGenesisBlock(nodes[3], 3, cons[nodes[3]])
+	b00 := s.prepareGenesisBlock(0, cons[nodes[0]])
+	b10 := s.prepareGenesisBlock(1, cons[nodes[1]])
+	b20 := s.prepareGenesisBlock(2, cons[nodes[2]])
+	b30 := s.prepareGenesisBlock(3, cons[nodes[3]])
 	for _, con := range cons {
 		req.Nil(con.processBlock(b00))
 		req.Nil(con.processBlock(b10))
@@ -335,74 +345,33 @@ func (s *ConsensusTestSuite) TestPrepareBlock() {
 		req.Nil(con.processBlock(b30))
 	}
 	b11 := &types.Block{
-		ProposerID: nodes[1],
+		Position: types.Position{ChainID: b10.Position.ChainID},
 	}
-	interval := gov.GetConfiguration(0).MinBlockInterval
+	interval := gov.Configuration(0).MinBlockInterval
 	req.Nil(cons[nodes[1]].prepareBlock(b11, b10.Timestamp.Add(interval)))
 	for _, con := range cons {
+		req.Nil(con.preProcessBlock(b11))
 		req.Nil(con.processBlock(b11))
 	}
 	b12 := &types.Block{
-		ProposerID: nodes[1],
+		Position: types.Position{ChainID: b11.Position.ChainID},
 	}
-	req.Nil(cons[nodes[1]].prepareBlock(b12, b10.Timestamp.Add(interval)))
+	req.Nil(cons[nodes[1]].prepareBlock(b12, b11.Timestamp.Add(interval)))
 	req.Len(b12.Acks, 1)
 	req.Contains(b12.Acks, b11.Hash)
 }
 
 func (s *ConsensusTestSuite) TestPrepareGenesisBlock() {
 	gov, err := test.NewGovernance(4, time.Second)
-	s.Require().Nil(err)
-	prvKey := gov.GetPrivateKeys()[0]
+	s.Require().NoError(err)
+	prvKey := gov.PrivateKeys()[0]
 	_, con := s.prepareConsensus(gov, prvKey)
 	block := &types.Block{
-		ProposerID: types.NewNodeID(prvKey.PublicKey()),
+		Position: types.Position{ChainID: 0},
 	}
-	con.PrepareGenesisBlock(block, time.Now().UTC())
+	s.Require().NoError(con.PrepareGenesisBlock(block, time.Now().UTC()))
 	s.True(block.IsGenesis())
-	s.Nil(con.sanityCheck(block))
-}
-
-func (s *ConsensusTestSuite) TestSanityCheck() {
-	gov, err := test.NewGovernance(4, time.Second)
-	s.Require().Nil(err)
-	prvKey := gov.GetPrivateKeys()[0]
-	_, con := s.prepareConsensus(gov, prvKey)
-	nID := types.NewNodeID(prvKey.PublicKey())
-	b0 := s.prepareGenesisBlock(nID, 0, con)
-	s.Require().NoError(con.processBlock(b0))
-	invalidChain := &types.Block{
-		ProposerID: nID,
-		Position: types.Position{
-			ChainID: 1000,
-		},
-	}
-	s.Equal(ErrIncorrectBlockPosition, con.sanityCheck(invalidChain))
-	invalidTimestamp := &types.Block{
-		ProposerID: nID,
-	}
-	s.Require().NoError(con.prepareBlock(invalidTimestamp, b0.Timestamp))
-	s.Equal(ErrIncorrectBlockTime, con.sanityCheck(invalidTimestamp))
-	s.Require().NoError(con.prepareBlock(invalidTimestamp, b0.Timestamp.Add(
-		gov.GetConfiguration(0).MaxBlockInterval).Add(1*time.Second)))
-	s.Equal(ErrIncorrectBlockTime, con.sanityCheck(invalidTimestamp))
-
-	ts := b0.Timestamp.Add(gov.GetConfiguration(0).MinBlockInterval)
-
-	invalidHash := &types.Block{
-		ProposerID: nID,
-	}
-	s.Require().NoError(con.prepareBlock(invalidHash, ts))
-	invalidHash.Hash = common.NewRandomHash()
-	s.Equal(ErrIncorrectHash, con.sanityCheck(invalidHash))
-
-	invalidSignature := &types.Block{
-		ProposerID: nID,
-	}
-	s.Require().NoError(con.prepareBlock(invalidSignature, ts))
-	invalidSignature.Signature, err = prvKey.Sign(common.NewRandomHash())
-	s.Require().NoError(err)
-	s.Equal(ErrIncorrectSignature, con.sanityCheck(invalidSignature))
+	s.NoError(con.preProcessBlock(block))
 }
 
 func TestConsensus(t *testing.T) {
diff --git a/core/interfaces.go b/core/interfaces.go
index d1868a5..fa593eb 100644
--- a/core/interfaces.go
+++ b/core/interfaces.go
@@ -79,27 +79,27 @@ type Network interface {
 // Note that there are a lot more methods in the governance contract, that this
 // interface only define those that are required to run the consensus algorithm.
 type Governance interface {
-	// GetConfiguration returns the configuration at a given round.
+	// Configuration returns the configuration at a given round.
 	// Return the genesis configuration if round == 0.
-	GetConfiguration(round uint64) *types.Config
+	Configuration(round uint64) *types.Config
 
-	// GetCRS returns the CRS for a given round.
+	// CRS returns the CRS for a given round.
 	// Return the genesis CRS if round == 0.
-	GetCRS(round uint64) common.Hash
+	CRS(round uint64) common.Hash
 
 	// Propose a CRS of round.
 	ProposeCRS(round uint64, signedCRS []byte)
 
-	// GetNodeSet returns the node set at a given round.
+	// NodeSet returns the node set at a given round.
 	// Return the genesis node set if round == 0.
-	GetNodeSet(round uint64) []crypto.PublicKey
+	NodeSet(round uint64) []crypto.PublicKey
 
 	//// DKG-related methods.
 
 	// AddDKGComplaint adds a DKGComplaint.
 	AddDKGComplaint(complaint *types.DKGComplaint)
 
-	// GetDKGComplaints gets all the DKGComplaints of round.
+	// DKGComplaints gets all the DKGComplaints of round.
 	DKGComplaints(round uint64) []*types.DKGComplaint
 
 	// AddDKGMasterPublicKey adds a DKGMasterPublicKey.
diff --git a/core/nodeset-cache.go b/core/nodeset-cache.go
index 610131b..49521ab 100644
--- a/core/nodeset-cache.go
+++ b/core/nodeset-cache.go
@@ -106,7 +106,7 @@ func (cache *NodeSetCache) update(
 	defer cache.lock.Unlock()
 
 	// Get the requested round from governance contract.
-	keySet := cache.gov.GetNodeSet(round)
+	keySet := cache.gov.NodeSet(round)
 	if keySet == nil {
 		// That round is not ready yet.
 		err = ErrRoundNotReady
diff --git a/core/nodeset-cache_test.go b/core/nodeset-cache_test.go
index 84e5d54..d7e7dba 100644
--- a/core/nodeset-cache_test.go
+++ b/core/nodeset-cache_test.go
@@ -32,10 +32,10 @@ type testGov struct {
 	curKeys []crypto.PublicKey
 }
 
-func (g *testGov) GetConfiguration(round uint64) (cfg *types.Config) { return }
-func (g *testGov) GetCRS(round uint64) (b common.Hash)               { return }
-func (g *testGov) ProposeCRS(uint64, []byte)                         {}
-func (g *testGov) GetNodeSet(round uint64) []crypto.PublicKey {
+func (g *testGov) Configuration(round uint64) (cfg *types.Config) { return }
+func (g *testGov) CRS(round uint64) (b common.Hash)               { return }
+func (g *testGov) ProposeCRS(uint64, []byte)                      {}
+func (g *testGov) NodeSet(round uint64) []crypto.PublicKey {
 	// Randomly generating keys, and check them for verification.
 	g.curKeys = []crypto.PublicKey{}
 	for i := 0; i < 10; i++ {
diff --git a/core/reliable-broadcast.go b/core/reliable-broadcast.go
deleted file mode 100644
index e8c5ca4..0000000
--- a/core/reliable-broadcast.go
+++ /dev/null
@@ -1,436 +0,0 @@
-// Copyright 2018 The dexon-consensus-core Authors
-// This file is part of the dexon-consensus-core library.
-//
-// The dexon-consensus-core library is free software: you can redistribute it
-// and/or modify it under the terms of the GNU Lesser General Public License as
-// published by the Free Software Foundation, either version 3 of the License,
-// or (at your option) any later version.
-//
-// The dexon-consensus-core library is distributed in the hope that it will be
-// useful, but WITHOUT ANY WARRANTY; without even the implied warranty of
-// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser
-// General Public License for more details.
-//
-// You should have received a copy of the GNU Lesser General Public License
-// along with the dexon-consensus-core library. If not, see
-// <http://www.gnu.org/licenses/>.
-
-package core
-
-import (
-	"fmt"
-	"time"
-
-	"github.com/dexon-foundation/dexon-consensus-core/common"
-	"github.com/dexon-foundation/dexon-consensus-core/core/types"
-)
-
-// Status represents the block process state.
-type blockStatus int
-
-// Block Status.
-const (
-	blockStatusInit blockStatus = iota
-	blockStatusAcked
-	blockStatusOrdering
-	blockStatusFinal
-)
-
-// reliableBroadcast is a module for reliable broadcast.
-type reliableBroadcast struct {
-	// lattice stores node's blocks and other info.
-	lattice []*rbcNodeStatus
-
-	// blockInfos stores block infos.
-	blockInfos map[common.Hash]*rbcBlockInfo
-
-	// receivedBlocks stores blocks which is received but its acks are not all
-	// in lattice.
-	receivedBlocks map[common.Hash]*types.Block
-
-	// nodes stores node set.
-	nodes map[types.NodeID]struct{}
-}
-
-type rbcNodeStatus struct {
-	// blocks stores blocks proposed by specified node in map which key is
-	// the height of the block.
-	blocks map[uint64]*types.Block
-
-	// nextAck stores the height of next height that should be acked, i.e. last
-	// acked height + 1. Initialized to 0, when genesis blocks are still not
-	// being acked. For example, rb.lattice[vid1].NextAck[vid2] - 1 is the last
-	// acked height by vid1 acking vid2.
-	nextAck []uint64
-
-	// nextOutput is the next output height of block, default to 0.
-	nextOutput uint64
-
-	// nextHeight is the next height of block to be prepared.
-	nextHeight uint64
-
-	// timestamp of the chain.
-	timestamp time.Time
-}
-
-type rbcBlockInfo struct {
-	block        *types.Block
-	receivedTime time.Time
-	status       blockStatus
-	ackedChain   map[uint32]struct{}
-}
-
-// Errors for sanity check error.
-var (
-	ErrInvalidChainID     = fmt.Errorf("invalid chain id")
-	ErrInvalidProposerID  = fmt.Errorf("invalid proposer id")
-	ErrInvalidTimestamp   = fmt.Errorf("invalid timestamp")
-	ErrForkBlock          = fmt.Errorf("fork block")
-	ErrNotAckParent       = fmt.Errorf("not ack parent")
-	ErrDoubleAck          = fmt.Errorf("double ack")
-	ErrInvalidBlockHeight = fmt.Errorf("invalid block height")
-	ErrAlreadyInLattice   = fmt.Errorf("block already in lattice")
-)
-
-// newReliableBroadcast creates a new reliableBroadcast struct.
-func newReliableBroadcast() *reliableBroadcast {
-	return &reliableBroadcast{
-		blockInfos:     make(map[common.Hash]*rbcBlockInfo),
-		receivedBlocks: make(map[common.Hash]*types.Block),
-		nodes:          make(map[types.NodeID]struct{}),
-	}
-}
-
-func (rb *reliableBroadcast) sanityCheck(b *types.Block) error {
-	// Check if the chain id is valid.
-	if b.Position.ChainID >= uint32(len(rb.lattice)) {
-		return ErrInvalidChainID
-	}
-
-	// Check if its proposer is in node set.
-	if _, exist := rb.nodes[b.ProposerID]; !exist {
-		return ErrInvalidProposerID
-	}
-
-	// Check if it forks.
-	if bInLattice, exist :=
-		rb.lattice[b.Position.ChainID].blocks[b.Position.Height]; exist {
-		if b.Hash != bInLattice.Hash {
-			return ErrForkBlock
-		}
-		return ErrAlreadyInLattice
-	}
-
-	// Check non-genesis blocks if it acks its parent.
-	if b.Position.Height > 0 {
-		if !b.IsAcking(b.ParentHash) {
-			return ErrNotAckParent
-		}
-		bParentStat, exists := rb.blockInfos[b.ParentHash]
-		if exists && bParentStat.block.Position.Height != b.Position.Height-1 {
-			return ErrInvalidBlockHeight
-		}
-	}
-
-	// Check if it acks older blocks.
-	for _, hash := range b.Acks {
-		if bAckStat, exist := rb.blockInfos[hash]; exist {
-			bAck := bAckStat.block
-			if bAck.Position.Height <
-				rb.lattice[b.Position.ChainID].nextAck[bAck.Position.ChainID] {
-				return ErrDoubleAck
-			}
-		}
-	}
-
-	// Check if its timestamp is valid.
-	if bParent, exist :=
-		rb.lattice[b.Position.ChainID].blocks[b.Position.Height-1]; exist {
-		if !b.Timestamp.After(bParent.Timestamp) {
-			return ErrInvalidTimestamp
-		}
-	}
-
-	// TODO(haoping): application layer check of block's content
-
-	return nil
-}
-
-// areAllAcksReceived checks if all ack blocks of a block are all in lattice.
-func (rb *reliableBroadcast) areAllAcksInLattice(b *types.Block) bool {
-	for _, h := range b.Acks {
-		bAckStat, exist := rb.blockInfos[h]
-		if !exist {
-			return false
-		}
-		bAck := bAckStat.block
-
-		bAckInLattice, exist :=
-			rb.lattice[bAck.Position.ChainID].blocks[bAck.Position.Height]
-		if !exist {
-			return false
-		}
-		if bAckInLattice.Hash != bAck.Hash {
-			panic("areAllAcksInLattice: reliableBroadcast.lattice has corrupted")
-		}
-	}
-	return true
-}
-
-// processBlock processes block, it does sanity check, inserts block into
-// lattice, handles strong acking and deletes blocks which will not be used.
-func (rb *reliableBroadcast) processBlock(block *types.Block) (err error) {
-	// If a block does not pass sanity check, discard this block.
-	if err = rb.sanityCheck(block); err != nil {
-		return
-	}
-	rb.blockInfos[block.Hash] = &rbcBlockInfo{
-		block:        block,
-		receivedTime: time.Now().UTC(),
-		ackedChain:   make(map[uint32]struct{}),
-	}
-	rb.receivedBlocks[block.Hash] = block
-	if rb.lattice[block.Position.ChainID].nextHeight <= block.Position.Height {
-		rb.lattice[block.Position.ChainID].nextHeight = block.Position.Height + 1
-	}
-	rb.lattice[block.Position.ChainID].timestamp = block.Timestamp
-
-	// Check blocks in receivedBlocks if its acks are all in lattice. If a block's
-	// acking blocks are all in lattice, execute sanity check and add the block
-	// into lattice.
-	blocksToAcked := map[common.Hash]*types.Block{}
-	for {
-		blocksToLattice := map[common.Hash]*types.Block{}
-		for _, b := range rb.receivedBlocks {
-			if rb.areAllAcksInLattice(b) {
-				blocksToLattice[b.Hash] = b
-			}
-		}
-		if len(blocksToLattice) == 0 {
-			break
-		}
-		for _, b := range blocksToLattice {
-			// Sanity check must been executed again here for the case that several
-			// valid blocks with different content being added into blocksToLattice
-			// in the same time. For example
-			// B   C  Block B and C both ack A and are valid. B, C received first
-			//  \ /   (added in receivedBlocks), and A comes, if sanity check is
-			//   A    not being executed here, B and C will both be added in lattice
-			if err = rb.sanityCheck(b); err != nil {
-				delete(rb.blockInfos, b.Hash)
-				delete(rb.receivedBlocks, b.Hash)
-				continue
-				// TODO(mission): how to return for multiple errors?
-			}
-			chainID := b.Position.ChainID
-			rb.lattice[chainID].blocks[b.Position.Height] = b
-			delete(rb.receivedBlocks, b.Hash)
-			for _, h := range b.Acks {
-				bAckStat := rb.blockInfos[h]
-				// Update nextAck only when bAckStat.block.Position.Height + 1
-				// is greater. A block might ack blocks proposed by same node with
-				// different height.
-				if rb.lattice[chainID].nextAck[bAckStat.block.Position.ChainID] <
-					bAckStat.block.Position.Height+1 {
-					rb.lattice[chainID].nextAck[bAckStat.block.Position.ChainID] =
-						bAckStat.block.Position.Height + 1
-				}
-				// Update ackedChain for each ack blocks and its parents.
-				for {
-					if _, exist := bAckStat.ackedChain[chainID]; exist {
-						break
-					}
-					if bAckStat.status > blockStatusInit {
-						break
-					}
-					bAckStat.ackedChain[chainID] = struct{}{}
-					// A block is strongly acked if it is acked by more than
-					// 2 * (maximum number of byzatine nodes) unique nodes.
-					if len(bAckStat.ackedChain) > 2*((len(rb.lattice)-1)/3) {
-						blocksToAcked[bAckStat.block.Hash] = bAckStat.block
-					}
-					if bAckStat.block.Position.Height == 0 {
-						break
-					}
-					bAckStat = rb.blockInfos[bAckStat.block.ParentHash]
-				}
-			}
-		}
-	}
-
-	for _, b := range blocksToAcked {
-		rb.blockInfos[b.Hash].status = blockStatusAcked
-	}
-
-	// Delete blocks in received array when it is received a long time ago.
-	oldBlocks := []common.Hash{}
-	for h, b := range rb.receivedBlocks {
-		if time.Now().Sub(rb.blockInfos[b.Hash].receivedTime) >= 30*time.Second {
-			oldBlocks = append(oldBlocks, h)
-		}
-	}
-	for _, h := range oldBlocks {
-		delete(rb.receivedBlocks, h)
-		delete(rb.blockInfos, h)
-	}
-
-	// Delete old blocks in "lattice" and "blocks" for release memory space.
-	// First, find the height that blocks below it can be deleted. This height
-	// is defined by finding minimum of node's nextOutput and last acking
-	// heights from other nodes, i.e. rb.lattice[v_other].nextAck[this_vid].
-	// This works because blocks of height below this minimum are not going to be
-	// acked anymore, the ackings of these blocks are illegal.
-	for vid := range rb.lattice {
-		// Find the minimum height that heights lesser can be deleted.
-		min := rb.lattice[vid].nextOutput
-		for vid2 := range rb.lattice {
-			if rb.lattice[vid2].nextAck[vid] < min {
-				min = rb.lattice[vid2].nextAck[vid]
-			}
-		}
-		// "min" is the height of "next" last acked, min - 1 is the last height.
-		// Delete blocks from min - 2 which will never be acked.
-		if min < 3 {
-			continue
-		}
-		min -= 2
-		for {
-			b, exist := rb.lattice[vid].blocks[min]
-			if !exist {
-				break
-			}
-			if rb.blockInfos[b.Hash].status >= blockStatusOrdering {
-				delete(rb.lattice[vid].blocks, b.Position.Height)
-				delete(rb.blockInfos, b.Hash)
-			}
-			if min == 0 {
-				break
-			}
-			min--
-		}
-	}
-	return
-}
-
-// extractBlocks returns all blocks that can be inserted into total ordering's
-// DAG. This function changes the status of blocks from blockStatusAcked to
-// blockStatusOrdering.
-func (rb *reliableBroadcast) extractBlocks() []*types.Block {
-	ret := []*types.Block{}
-	for {
-		updated := false
-		for vid := range rb.lattice {
-			b, exist := rb.lattice[vid].blocks[rb.lattice[vid].nextOutput]
-			if !exist || rb.blockInfos[b.Hash].status < blockStatusAcked {
-				continue
-			}
-			allAcksInOrderingStatus := true
-			// Check if all acks are in ordering or above status. If a block of an ack
-			// does not exist means that it deleted but its status is definitely Acked
-			// or ordering.
-			for _, ackHash := range b.Acks {
-				bAckStat, exist := rb.blockInfos[ackHash]
-				if !exist {
-					continue
-				}
-				if bAckStat.status < blockStatusOrdering {
-					allAcksInOrderingStatus = false
-					break
-				}
-			}
-			if !allAcksInOrderingStatus {
-				continue
-			}
-			updated = true
-			rb.blockInfos[b.Hash].status = blockStatusOrdering
-			ret = append(ret, b)
-			rb.lattice[vid].nextOutput++
-		}
-		if !updated {
-			break
-		}
-	}
-	return ret
-}
-
-// prepareBlock helps to setup fields of block based on its ProposerID,
-// including:
-//  - Set 'Acks' and 'Timestamps' for the highest block of each node not
-//    acked by this proposer before.
-//  - Set 'ParentHash' and 'Height' from parent block, if we can't find a
-//    parent, these fields would be setup like a genesis block.
-func (rb *reliableBroadcast) prepareBlock(block *types.Block) {
-	// Reset fields to make sure we got these information from parent block.
-	block.Position.Height = 0
-	block.ParentHash = common.Hash{}
-	acks := common.Hashes{}
-	for chainID := range rb.lattice {
-		// find height of the latest block for that node.
-		var (
-			curBlock   *types.Block
-			nextHeight = rb.lattice[block.Position.ChainID].nextAck[chainID]
-		)
-
-		for {
-			tmpBlock, exists := rb.lattice[chainID].blocks[nextHeight]
-			if !exists {
-				break
-			}
-			curBlock = tmpBlock
-			nextHeight++
-		}
-		if curBlock == nil {
-			continue
-		}
-		acks = append(acks, curBlock.Hash)
-		if uint32(chainID) == block.Position.ChainID {
-			block.ParentHash = curBlock.Hash
-			if block.Timestamp.Before(curBlock.Timestamp) {
-				// TODO (mission): make epslon configurable.
-				block.Timestamp = curBlock.Timestamp.Add(1 * time.Millisecond)
-			}
-			if block.Position.Height == 0 {
-				block.Position.Height = curBlock.Position.Height + 1
-			}
-		}
-	}
-	block.Acks = common.NewSortedHashes(acks)
-	return
-}
-
-// addNode adds node in the node set.
-func (rb *reliableBroadcast) addNode(h types.NodeID) {
-	rb.nodes[h] = struct{}{}
-}
-
-// deleteNode deletes node in node set.
-func (rb *reliableBroadcast) deleteNode(h types.NodeID) {
-	delete(rb.nodes, h)
-}
-
-// setChainNum set the number of chains.
-func (rb *reliableBroadcast) setChainNum(num uint32) {
-	rb.lattice = make([]*rbcNodeStatus, num)
-	for i := range rb.lattice {
-		rb.lattice[i] = &rbcNodeStatus{
-			blocks:     make(map[uint64]*types.Block),
-			nextAck:    make([]uint64, num),
-			nextOutput: 0,
-			nextHeight: 0,
-		}
-	}
-}
-
-func (rb *reliableBroadcast) chainNum() uint32 {
-	return uint32(len(rb.lattice))
-}
-
-// nextHeight returns the next height for the chain.
-func (rb *reliableBroadcast) nextHeight(chainID uint32) uint64 {
-	return rb.lattice[chainID].nextHeight
-}
-
-// chainTime returnes the latest time for the chain.
-func (rb *reliableBroadcast) chainTime(chainID uint32) time.Time {
-	return rb.lattice[chainID].timestamp
-}
diff --git a/core/reliable-broadcast_test.go b/core/reliable-broadcast_test.go
deleted file mode 100644
index 0e627d1..0000000
--- a/core/reliable-broadcast_test.go
+++ /dev/null
@@ -1,702 +0,0 @@
-// Copyright 2018 The dexon-consensus-core Authors
-// This file is part of the dexon-consensus-core library.
-//
-// The dexon-consensus-core library is free software: you can redistribute it
-// and/or modify it under the terms of the GNU Lesser General Public License as
-// published by the Free Software Foundation, either version 3 of the License,
-// or (at your option) any later version.
-//
-// The dexon-consensus-core library is distributed in the hope that it will be
-// useful, but WITHOUT ANY WARRANTY; without even the implied warranty of
-// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser
-// General Public License for more details.
-//
-// You should have received a copy of the GNU Lesser General Public License
-// along with the dexon-consensus-core library. If not, see
-// <http://www.gnu.org/licenses/>.
-
-// TODO(mission): we should check the return value from processBlock.
-
-package core
-
-import (
-	"math/rand"
-	"sort"
-	"testing"
-	"time"
-
-	"github.com/stretchr/testify/suite"
-
-	"github.com/dexon-foundation/dexon-consensus-core/common"
-	"github.com/dexon-foundation/dexon-consensus-core/core/blockdb"
-	"github.com/dexon-foundation/dexon-consensus-core/core/test"
-	"github.com/dexon-foundation/dexon-consensus-core/core/types"
-)
-
-type ReliableBroadcastTest struct {
-	suite.Suite
-}
-
-func (s *ReliableBroadcastTest) SetupSuite() {
-
-}
-
-func (s *ReliableBroadcastTest) SetupTest() {
-
-}
-
-func (s *ReliableBroadcastTest) prepareGenesisBlock(
-	proposerID types.NodeID,
-	nodeIDs []types.NodeID) (b *types.Block) {
-
-	b = &types.Block{
-		ProposerID: proposerID,
-		ParentHash: common.Hash{},
-		Position: types.Position{
-			Height: 0,
-		},
-		Acks:      common.NewSortedHashes(common.Hashes{}),
-		Timestamp: time.Now().UTC(),
-	}
-	for i, vID := range nodeIDs {
-		if proposerID == vID {
-			b.Position.ChainID = uint32(i)
-			break
-		}
-	}
-	b.Timestamp = time.Now().UTC()
-	var err error
-	b.Hash, err = hashBlock(b)
-	s.Require().Nil(err)
-	return
-}
-
-// genTestCase1 generates test case 1,
-//  3
-//  |
-//  2
-//  | \
-//  1  |     1
-//  |  |     |
-//  0  0  0  0 (block height)
-//  0  1  2  3 (node)
-func genTestCase1(s *ReliableBroadcastTest, rb *reliableBroadcast) []types.NodeID {
-	// Create new reliableBroadcast instance with 4 nodes
-	var b *types.Block
-	var h common.Hash
-
-	vids := []types.NodeID{}
-	for i := 0; i < 4; i++ {
-		vid := types.NodeID{Hash: common.NewRandomHash()}
-		rb.addNode(vid)
-		vids = append(vids, vid)
-	}
-	rb.setChainNum(uint32(len(vids)))
-	// Add genesis blocks.
-	for _, vid := range vids {
-		b = s.prepareGenesisBlock(vid, vids)
-		s.Require().Nil(rb.processBlock(b))
-	}
-
-	// Add block 0-1 which acks 0-0.
-	h = rb.lattice[0].blocks[0].Hash
-	b = &types.Block{
-		ProposerID: vids[0],
-		ParentHash: h,
-		Hash:       common.NewRandomHash(),
-		Timestamp:  time.Now().UTC(),
-		Position: types.Position{
-			ChainID: 0,
-			Height:  1,
-		},
-		Acks: common.NewSortedHashes(common.Hashes{h}),
-	}
-	var err error
-	b.Hash, err = hashBlock(b)
-	s.Require().Nil(err)
-	s.Require().Nil(rb.processBlock(b))
-	s.Require().NotNil(rb.lattice[0].blocks[1])
-
-	// Add block 0-2 which acks 0-1 and 1-0.
-	h = rb.lattice[0].blocks[1].Hash
-	b = &types.Block{
-		ProposerID: vids[0],
-		ParentHash: h,
-		Position: types.Position{
-			ChainID: 0,
-			Height:  2,
-		},
-		Timestamp: time.Now().UTC(),
-		Acks: common.NewSortedHashes(common.Hashes{
-			h,
-			rb.lattice[1].blocks[0].Hash,
-		}),
-	}
-	b.Hash, err = hashBlock(b)
-	s.Require().Nil(err)
-	s.Require().Nil(rb.processBlock(b))
-	s.Require().NotNil(rb.lattice[0].blocks[2])
-
-	// Add block 0-3 which acks 0-2.
-	h = rb.lattice[0].blocks[2].Hash
-	b = &types.Block{
-		ProposerID: vids[0],
-		ParentHash: h,
-		Hash:       common.NewRandomHash(),
-		Timestamp:  time.Now().UTC(),
-		Position: types.Position{
-			ChainID: 0,
-			Height:  3,
-		},
-		Acks: common.NewSortedHashes(common.Hashes{h}),
-	}
-	b.Hash, err = hashBlock(b)
-	s.Require().Nil(err)
-	s.Require().Nil(rb.processBlock(b))
-	s.Require().NotNil(rb.lattice[0].blocks[3])
-
-	// Add block 3-1 which acks 3-0.
-	h = rb.lattice[3].blocks[0].Hash
-	b = &types.Block{
-		ProposerID: vids[3],
-		ParentHash: h,
-		Hash:       common.NewRandomHash(),
-		Timestamp:  time.Now().UTC(),
-		Position: types.Position{
-			ChainID: 3,
-			Height:  1,
-		},
-		Acks: common.NewSortedHashes(common.Hashes{h}),
-	}
-	b.Hash, err = hashBlock(b)
-	s.Require().Nil(err)
-	s.Require().Nil(rb.processBlock(b))
-	s.Require().NotNil(rb.lattice[3].blocks[0])
-
-	return vids
-}
-
-func (s *ReliableBroadcastTest) TestAddNode() {
-	rb := newReliableBroadcast()
-	s.Require().Equal(len(rb.lattice), 0)
-	vids := genTestCase1(s, rb)
-	s.Require().Equal(len(rb.lattice), 4)
-	for _, vid := range vids {
-		rb.deleteNode(vid)
-	}
-}
-
-func (s *ReliableBroadcastTest) TestSanityCheck() {
-	var b *types.Block
-	var h common.Hash
-	var vids []types.NodeID
-	var err error
-	rb := newReliableBroadcast()
-	vids = genTestCase1(s, rb)
-
-	// Non-genesis block with no ack, should get error.
-	b = &types.Block{
-		ProposerID: vids[0],
-		ParentHash: common.NewRandomHash(),
-		Position: types.Position{
-			ChainID: 0,
-			Height:  10,
-		},
-		Acks: common.NewSortedHashes(common.Hashes{}),
-	}
-	b.Hash, err = hashBlock(b)
-	s.Require().Nil(err)
-	err = rb.sanityCheck(b)
-	s.Require().NotNil(err)
-	s.Require().Equal(ErrNotAckParent.Error(), err.Error())
-
-	// Non-genesis block which does not ack its parent.
-	b = &types.Block{
-		ProposerID: vids[1],
-		ParentHash: common.NewRandomHash(),
-		Position: types.Position{
-			ChainID: 1,
-			Height:  1,
-		},
-		Acks: common.NewSortedHashes(
-			common.Hashes{rb.lattice[2].blocks[0].Hash}),
-	}
-	b.Hash, err = hashBlock(b)
-	s.Require().Nil(err)
-	err = rb.sanityCheck(b)
-	s.Require().NotNil(err)
-	s.Require().Equal(ErrNotAckParent.Error(), err.Error())
-
-	// Non-genesis block which acks its parent but the height is invalid.
-	h = rb.lattice[1].blocks[0].Hash
-	b = &types.Block{
-		ProposerID: vids[1],
-		ParentHash: h,
-		Position: types.Position{
-			ChainID: 1,
-			Height:  2,
-		},
-		Acks: common.NewSortedHashes(common.Hashes{h}),
-	}
-	b.Hash, err = hashBlock(b)
-	s.Require().Nil(err)
-	err = rb.sanityCheck(b)
-	s.Require().NotNil(err)
-	s.Require().Equal(ErrInvalidBlockHeight.Error(), err.Error())
-
-	// Invalid proposer ID.
-	h = rb.lattice[1].blocks[0].Hash
-	b = &types.Block{
-		ProposerID: types.NodeID{Hash: common.NewRandomHash()},
-		ParentHash: h,
-		Position: types.Position{
-			Height: 1,
-		},
-		Acks: common.NewSortedHashes(common.Hashes{h}),
-	}
-	b.Hash, err = hashBlock(b)
-	s.Require().Nil(err)
-	err = rb.sanityCheck(b)
-	s.Require().NotNil(err)
-	s.Require().Equal(ErrInvalidProposerID.Error(), err.Error())
-
-	// Invalid chain ID.
-	h = rb.lattice[1].blocks[0].Hash
-	b = &types.Block{
-		ProposerID: vids[1],
-		ParentHash: h,
-		Position: types.Position{
-			ChainID: 100,
-			Height:  1,
-		},
-		Acks: common.NewSortedHashes(common.Hashes{h}),
-	}
-	b.Hash, err = hashBlock(b)
-	s.Require().Nil(err)
-	err = rb.sanityCheck(b)
-	s.Require().NotNil(err)
-	s.Require().Equal(ErrInvalidChainID.Error(), err.Error())
-
-	// Fork block.
-	h = rb.lattice[0].blocks[0].Hash
-	b = &types.Block{
-		ProposerID: vids[0],
-		ParentHash: h,
-		Position: types.Position{
-			ChainID: 0,
-			Height:  1,
-		},
-		Acks:      common.NewSortedHashes(common.Hashes{h}),
-		Timestamp: time.Now().UTC(),
-	}
-	b.Hash, err = hashBlock(b)
-	s.Require().Nil(err)
-	err = rb.sanityCheck(b)
-	s.Require().NotNil(err)
-	s.Require().Equal(ErrForkBlock.Error(), err.Error())
-
-	// Replicated ack.
-	h = rb.lattice[0].blocks[3].Hash
-	b = &types.Block{
-		ProposerID: vids[0],
-		ParentHash: h,
-		Position: types.Position{
-			ChainID: 0,
-			Height:  4,
-		},
-		Acks: common.NewSortedHashes(common.Hashes{
-			h,
-			rb.lattice[1].blocks[0].Hash,
-		}),
-	}
-	b.Hash, err = hashBlock(b)
-	s.Require().Nil(err)
-	err = rb.sanityCheck(b)
-	s.Require().NotNil(err)
-	s.Require().Equal(ErrDoubleAck.Error(), err.Error())
-
-	// Normal block.
-	h = rb.lattice[1].blocks[0].Hash
-	b = &types.Block{
-		ProposerID: vids[1],
-		ParentHash: h,
-		Position: types.Position{
-			ChainID: 1,
-			Height:  1,
-		},
-		Acks: common.NewSortedHashes(common.Hashes{
-			h,
-			common.NewRandomHash(),
-		}),
-		Timestamp: time.Now().UTC(),
-	}
-	b.Hash, err = hashBlock(b)
-	s.Require().Nil(err)
-	err = rb.sanityCheck(b)
-	s.Nil(err)
-}
-
-func (s *ReliableBroadcastTest) TestAreAllAcksInLattice() {
-	var b *types.Block
-	rb := newReliableBroadcast()
-	genTestCase1(s, rb)
-
-	// Empty ack should get true, although won't pass sanity check.
-	b = &types.Block{
-		Acks: common.NewSortedHashes(common.Hashes{}),
-	}
-	s.Require().True(rb.areAllAcksInLattice(b))
-
-	// Acks blocks in lattice
-	b = &types.Block{
-		Acks: common.NewSortedHashes(common.Hashes{
-			rb.lattice[0].blocks[0].Hash,
-			rb.lattice[0].blocks[1].Hash,
-		}),
-	}
-	s.Require().True(rb.areAllAcksInLattice(b))
-
-	// Acks random block hash.
-	b = &types.Block{
-		Acks: common.NewSortedHashes(common.Hashes{common.NewRandomHash()}),
-	}
-	s.Require().False(rb.areAllAcksInLattice(b))
-}
-
-func (s *ReliableBroadcastTest) TestStrongAck() {
-	var b *types.Block
-	var vids []types.NodeID
-
-	rb := newReliableBroadcast()
-	vids = genTestCase1(s, rb)
-
-	// Check block 0-0 to 0-3 before adding 1-1 and 2-1.
-	for i := uint64(0); i < 4; i++ {
-		s.Require().Equal(blockStatusInit, rb.blockInfos[rb.lattice[0].blocks[i].Hash].status)
-	}
-
-	// Add block 1-1 which acks 1-0 and 0-2, and block 0-0 to 0-3 are still
-	// in blockStatusInit, because they are not strongly acked.
-	b = &types.Block{
-		ProposerID: vids[1],
-		ParentHash: rb.lattice[1].blocks[0].Hash,
-		Hash:       common.NewRandomHash(),
-		Position: types.Position{
-			ChainID: 1,
-			Height:  1,
-		},
-		Timestamp: time.Now().UTC(),
-		Acks: common.NewSortedHashes(common.Hashes{
-			rb.lattice[0].blocks[2].Hash,
-			rb.lattice[1].blocks[0].Hash,
-		}),
-	}
-	var err error
-	b.Hash, err = hashBlock(b)
-	s.Require().Nil(err)
-	s.Require().Nil(rb.processBlock(b))
-	s.Require().NotNil(rb.lattice[1].blocks[1])
-	for i := uint64(0); i < 4; i++ {
-		h := rb.lattice[0].blocks[i].Hash
-		s.Require().Equal(blockStatusInit, rb.blockInfos[h].status)
-	}
-
-	// Add block 2-1 which acks 0-2 and 2-0, block 0-0 to 0-2 are strongly acked but
-	// 0-3 is still not.
-	b = &types.Block{
-		ProposerID: vids[2],
-		ParentHash: rb.lattice[2].blocks[0].Hash,
-		Hash:       common.NewRandomHash(),
-		Position: types.Position{
-			ChainID: 2,
-			Height:  1,
-		},
-		Timestamp: time.Now().UTC(),
-		Acks: common.NewSortedHashes(common.Hashes{
-			rb.lattice[0].blocks[2].Hash,
-			rb.lattice[2].blocks[0].Hash,
-		}),
-	}
-	b.Hash, err = hashBlock(b)
-	s.Require().Nil(err)
-	s.Require().Nil(rb.processBlock(b))
-
-	s.Require().Equal(blockStatusAcked, rb.blockInfos[rb.lattice[0].blocks[0].Hash].status)
-	s.Require().Equal(blockStatusAcked, rb.blockInfos[rb.lattice[0].blocks[1].Hash].status)
-	s.Require().Equal(blockStatusAcked, rb.blockInfos[rb.lattice[0].blocks[2].Hash].status)
-	s.Require().Equal(blockStatusInit, rb.blockInfos[rb.lattice[0].blocks[3].Hash].status)
-}
-
-func (s *ReliableBroadcastTest) TestExtractBlocks() {
-	var b *types.Block
-	rb := newReliableBroadcast()
-	vids := genTestCase1(s, rb)
-
-	// Add block 1-1 which acks 1-0, 0-2, 3-0.
-	b = &types.Block{
-		ProposerID: vids[1],
-		ParentHash: rb.lattice[1].blocks[0].Hash,
-		Hash:       common.NewRandomHash(),
-		Position: types.Position{
-			ChainID: 1,
-			Height:  1,
-		},
-		Timestamp: time.Now().UTC(),
-		Acks: common.NewSortedHashes(common.Hashes{
-			rb.lattice[0].blocks[2].Hash,
-			rb.lattice[1].blocks[0].Hash,
-			rb.lattice[3].blocks[0].Hash,
-		}),
-	}
-	var err error
-	b.Hash, err = hashBlock(b)
-	s.Require().Nil(err)
-	s.Require().Nil(rb.processBlock(b))
-
-	// Add block 2-1 which acks 0-2, 2-0, 3-0.
-	b = &types.Block{
-		ProposerID: vids[2],
-		ParentHash: rb.lattice[2].blocks[0].Hash,
-		Hash:       common.NewRandomHash(),
-		Position: types.Position{
-			ChainID: 2,
-			Height:  1,
-		},
-		Timestamp: time.Now().UTC(),
-		Acks: common.NewSortedHashes(common.Hashes{
-			rb.lattice[0].blocks[2].Hash,
-			rb.lattice[2].blocks[0].Hash,
-			rb.lattice[3].blocks[0].Hash,
-		}),
-	}
-	b.Hash, err = hashBlock(b)
-	s.Require().Nil(err)
-	s.Require().Nil(rb.processBlock(b))
-
-	hashes := []common.Hash{
-		rb.lattice[0].blocks[0].Hash,
-		rb.lattice[0].blocks[1].Hash,
-		rb.lattice[3].blocks[0].Hash,
-	}
-	hashExtracted := map[common.Hash]*types.Block{}
-	for _, b := range rb.extractBlocks() {
-		hashExtracted[b.Hash] = b
-		s.Require().Equal(blockStatusOrdering, rb.blockInfos[b.Hash].status)
-	}
-	for _, h := range hashes {
-		_, exist := hashExtracted[h]
-		s.Require().True(exist)
-	}
-}
-
-func (s *ReliableBroadcastTest) TestRandomIntensiveAcking() {
-	rb := newReliableBroadcast()
-	vids := test.GenerateRandomNodeIDs(4)
-	heights := map[types.NodeID]uint64{}
-	extractedBlocks := []*types.Block{}
-
-	// Generate nodes.
-	for _, vid := range vids {
-		rb.addNode(vid)
-	}
-	rb.setChainNum(uint32(len(vids)))
-	// Generate genesis blocks.
-	for _, vid := range vids {
-		b := s.prepareGenesisBlock(vid, vids)
-		s.Require().Nil(rb.processBlock(b))
-		heights[vid] = 1
-	}
-
-	for i := 0; i < 5000; i++ {
-		id := rand.Int() % len(vids)
-		vid := vids[id]
-		height := heights[vid]
-		heights[vid]++
-		parentHash := rb.lattice[id].blocks[height-1].Hash
-		acks := common.Hashes{}
-		for id2 := range vids {
-			if b, exist := rb.lattice[id2].blocks[rb.lattice[id].nextAck[id2]]; exist {
-				acks = append(acks, b.Hash)
-			}
-		}
-		b := &types.Block{
-			ProposerID: vid,
-			ParentHash: parentHash,
-			Position: types.Position{
-				ChainID: uint32(id),
-				Height:  height,
-			},
-			Timestamp: time.Now().UTC(),
-			Acks:      common.NewSortedHashes(acks),
-		}
-		var err error
-		b.Hash, err = hashBlock(b)
-		s.Require().Nil(err)
-		s.Require().Nil(rb.processBlock(b))
-		extractedBlocks = append(extractedBlocks, rb.extractBlocks()...)
-	}
-
-	extractedBlocks = append(extractedBlocks, rb.extractBlocks()...)
-	// The len of array extractedBlocks should be about 5000.
-	s.Require().True(len(extractedBlocks) > 4500)
-	// The len of rb.blockInfos should be small if deleting mechanism works.
-	// s.True(len(rb.blockInfos) < 500)
-}
-
-func (s *ReliableBroadcastTest) TestRandomlyGeneratedBlocks() {
-	var (
-		chainNum = uint32(19)
-		blockNum = 50
-		repeat   = 20
-	)
-
-	// Prepare a randomly generated blocks.
-	db, err := blockdb.NewMemBackedBlockDB("test-reliable-broadcast-random.blockdb")
-	s.Require().Nil(err)
-	defer func() {
-		// If the test fails, keep the block database for troubleshooting.
-		if s.T().Failed() {
-			s.Nil(db.Close())
-		}
-	}()
-	gen := test.NewBlocksGenerator(nil, hashBlock)
-	_, err = gen.Generate(chainNum, blockNum, nil, db)
-	s.Require().Nil(err)
-	iter, err := db.GetAll()
-	s.Require().Nil(err)
-	// Setup a revealer that would reveal blocks randomly.
-	revealer, err := test.NewRandomRevealer(iter)
-	s.Require().Nil(err)
-
-	stronglyAckedHashesAsString := map[string]struct{}{}
-	for i := 0; i < repeat; i++ {
-		nodes := map[types.NodeID]struct{}{}
-		rb := newReliableBroadcast()
-		rb.setChainNum(chainNum)
-		stronglyAckedHashes := common.Hashes{}
-		revealer.Reset()
-
-		for {
-			// Reveal next block.
-			b, err := revealer.Next()
-			if err != nil {
-				if err == blockdb.ErrIterationFinished {
-					err = nil
-					break
-				}
-			}
-			s.Require().Nil(err)
-
-			// It's a hack to add node to reliableBroadcast module.
-			if _, added := nodes[b.ProposerID]; !added {
-				rb.addNode(b.ProposerID)
-				nodes[b.ProposerID] = struct{}{}
-			}
-			// Perform reliable broadcast process.
-			s.Require().Nil(rb.processBlock(&b))
-			for _, b := range rb.extractBlocks() {
-				stronglyAckedHashes = append(stronglyAckedHashes, b.Hash)
-			}
-		}
-		// To make it easier to check, sort hashes of
-		// strongly acked blocks, and concatenate them into
-		// a string.
-		sort.Sort(stronglyAckedHashes)
-		asString := ""
-		for _, h := range stronglyAckedHashes {
-			asString += h.String() + ","
-		}
-		stronglyAckedHashesAsString[asString] = struct{}{}
-	}
-	// Make sure concatenated hashes of strongly acked blocks are identical.
-	s.Require().Len(stronglyAckedHashesAsString, 1)
-	for h := range stronglyAckedHashesAsString {
-		// Make sure at least some blocks are strongly acked.
-		s.True(len(h) > 0)
-	}
-}
-
-func (s *ReliableBroadcastTest) TestPrepareBlock() {
-	var (
-		req         = s.Require()
-		rb          = newReliableBroadcast()
-		minInterval = 50 * time.Millisecond
-		nodes       = test.GenerateRandomNodeIDs(4)
-	)
-	// Prepare node IDs.
-	for _, vID := range nodes {
-		rb.addNode(vID)
-	}
-	rb.setChainNum(uint32(len(nodes)))
-	// Setup genesis blocks.
-	b00 := s.prepareGenesisBlock(nodes[0], nodes)
-	time.Sleep(minInterval)
-	b10 := s.prepareGenesisBlock(nodes[1], nodes)
-	time.Sleep(minInterval)
-	b20 := s.prepareGenesisBlock(nodes[2], nodes)
-	time.Sleep(minInterval)
-	b30 := s.prepareGenesisBlock(nodes[3], nodes)
-	// Submit these blocks to reliableBroadcast instance.
-	s.Require().Nil(rb.processBlock(b00))
-	s.Require().Nil(rb.processBlock(b10))
-	s.Require().Nil(rb.processBlock(b20))
-	s.Require().Nil(rb.processBlock(b30))
-	// We should be able to collect all 4 genesis blocks by calling
-	// prepareBlock.
-	b11 := &types.Block{
-		ProposerID: nodes[1],
-		Position: types.Position{
-			ChainID: 1,
-		},
-	}
-	rb.prepareBlock(b11)
-	var err error
-	b11.Hash, err = hashBlock(b11)
-	s.Require().Nil(err)
-	req.Contains(b11.Acks, b00.Hash)
-	req.Contains(b11.Acks, b10.Hash)
-	req.Contains(b11.Acks, b20.Hash)
-	req.Contains(b11.Acks, b30.Hash)
-	req.Equal(b11.Timestamp,
-		b10.Timestamp.Add(time.Millisecond))
-	req.Equal(b11.ParentHash, b10.Hash)
-	req.Equal(b11.Position.Height, uint64(1))
-	s.Require().Nil(rb.processBlock(b11))
-	// Propose/Process a block based on collected info.
-	b12 := &types.Block{
-		ProposerID: nodes[1],
-		Position: types.Position{
-			ChainID: 1,
-		},
-	}
-	rb.prepareBlock(b12)
-	b12.Hash, err = hashBlock(b12)
-	s.Require().Nil(err)
-	// This time we only need to ack b11.
-	req.Len(b12.Acks, 1)
-	req.Contains(b12.Acks, b11.Hash)
-	req.Equal(b12.ParentHash, b11.Hash)
-	req.Equal(b12.Position.Height, uint64(2))
-	// When calling with other node ID, we should be able to
-	// get 4 blocks to ack.
-	b01 := &types.Block{
-		ProposerID: nodes[0],
-		Position: types.Position{
-			ChainID: 0,
-		},
-	}
-	rb.prepareBlock(b01)
-	b01.Hash, err = hashBlock(b01)
-	s.Require().Nil(err)
-	req.Len(b01.Acks, 4)
-	req.Contains(b01.Acks, b00.Hash)
-	req.Contains(b01.Acks, b11.Hash)
-	req.Contains(b01.Acks, b20.Hash)
-	req.Contains(b01.Acks, b30.Hash)
-	req.Equal(b01.ParentHash, b00.Hash)
-	req.Equal(b01.Position.Height, uint64(1))
-}
-
-func TestReliableBroadcast(t *testing.T) {
-	suite.Run(t, new(ReliableBroadcastTest))
-}
diff --git a/core/shard.go b/core/shard.go
index 32f1b79..7085872 100644
--- a/core/shard.go
+++ b/core/shard.go
@@ -30,7 +30,6 @@ import (
 // Shard represents a unit to produce a global ordering from multiple chains.
 type Shard struct {
 	lock       sync.RWMutex
-	ID         uint32
 	authModule *Authenticator
 	chainNum   uint32
 	app        Application
@@ -44,22 +43,23 @@ type Shard struct {
 
 // NewShard constructs an Shard instance.
 func NewShard(
-	ID uint32,
 	cfg *types.Config,
 	authModule *Authenticator,
 	app Application,
 	debug Debug,
 	db blockdb.BlockDatabase) (s *Shard) {
-
+	lattice := newBlockLattice(
+		cfg.NumChains,
+		cfg.MinBlockInterval,
+		cfg.MaxBlockInterval)
 	s = &Shard{
-		ID:         ID,
 		authModule: authModule,
 		chainNum:   cfg.NumChains,
 		app:        app,
 		debug:      debug,
 		db:         db,
 		pool:       newBlockPool(cfg.NumChains),
-		lattice:    newBlockLattice(ID, cfg.NumChains),
+		lattice:    lattice,
 		toModule: newTotalOrdering(
 			uint64(cfg.K),
 			uint64(float32(cfg.NumChains-1)*cfg.PhiRatio+1),
@@ -188,3 +188,11 @@ func (s *Shard) ProcessBlock(
 	}
 	return
 }
+
+// NextPosition returns expected position of incoming block for that chain.
+func (s *Shard) NextPosition(chainID uint32) types.Position {
+	s.lock.RLock()
+	defer s.lock.RUnlock()
+
+	return s.lattice.nextPosition(chainID)
+}
diff --git a/core/shard_test.go b/core/shard_test.go
index d4ceffd..84f230b 100644
--- a/core/shard_test.go
+++ b/core/shard_test.go
@@ -22,6 +22,7 @@ import (
 	"testing"
 	"time"
 
+	"github.com/dexon-foundation/dexon-consensus-core/common"
 	"github.com/dexon-foundation/dexon-consensus-core/core/blockdb"
 	"github.com/dexon-foundation/dexon-consensus-core/core/crypto/ecdsa"
 	"github.com/dexon-foundation/dexon-consensus-core/core/test"
@@ -105,7 +106,6 @@ func (s *ShardTestSuite) newTestShardMgr(cfg *types.Config) *testShardMgr {
 		app:      app,
 		db:       db,
 		shard: NewShard(
-			uint32(0),
 			cfg,
 			NewAuthenticator(prvKey),
 			app,
@@ -124,9 +124,11 @@ func (s *ShardTestSuite) TestBasicUsage() {
 		req           = s.Require()
 		err           error
 		cfg           = types.Config{
-			NumChains: chainNum,
-			PhiRatio:  float32(2) / float32(3),
-			K:         0,
+			NumChains:        chainNum,
+			PhiRatio:         float32(2) / float32(3),
+			K:                0,
+			MinBlockInterval: 0,
+			MaxBlockInterval: 3000 * time.Second,
 		}
 		master    = s.newTestShardMgr(&cfg)
 		apps      = []*test.App{master.app}
@@ -187,6 +189,37 @@ func (s *ShardTestSuite) TestBasicUsage() {
 	}
 }
 
+func (s *ShardTestSuite) TestSanityCheck() {
+	// This sanity check focuses on hash/signature part.
+	var (
+		chainNum = uint32(19)
+		cfg      = types.Config{
+			NumChains:        chainNum,
+			PhiRatio:         float32(2) / float32(3),
+			K:                0,
+			MinBlockInterval: 0,
+			MaxBlockInterval: 3000 * time.Second,
+		}
+		shard = s.newTestShardMgr(&cfg).shard
+		auth  = shard.authModule // Steal auth module from shard, :(
+		req   = s.Require()
+		err   error
+	)
+	// A block properly signed should pass sanity check.
+	b := &types.Block{
+		Position: types.Position{ChainID: 0},
+	}
+	req.NoError(auth.SignBlock(b))
+	req.NoError(shard.SanityCheck(b))
+	// A block with incorrect signature should not pass sanity check.
+	b.Signature, err = auth.prvKey.Sign(common.NewRandomHash())
+	req.NoError(err)
+	req.Equal(shard.SanityCheck(b), ErrIncorrectSignature)
+	// A block with incorrect hash should not pass sanity check.
+	b.Hash = common.NewRandomHash()
+	req.Equal(shard.SanityCheck(b), ErrIncorrectHash)
+}
+
 func TestShard(t *testing.T) {
 	suite.Run(t, new(ShardTestSuite))
 }
diff --git a/core/test/governance.go b/core/test/governance.go
index 6ae2462..ee4491f 100644
--- a/core/test/governance.go
+++ b/core/test/governance.go
@@ -62,7 +62,7 @@ func NewGovernance(nodeCount int, lambda time.Duration) (
 		DKGComplaint:       make(map[uint64][]*types.DKGComplaint),
 		DKGMasterPublicKey: make(map[uint64][]*types.DKGMasterPublicKey),
 		RoundInterval:      365 * 86400 * time.Second,
-		MinBlockInterval:   lambda * 3,
+		MinBlockInterval:   1 * time.Millisecond,
 		MaxBlockInterval:   lambda * 8,
 	}
 	for i := 0; i < nodeCount; i++ {
@@ -76,9 +76,9 @@ func NewGovernance(nodeCount int, lambda time.Duration) (
 	return
 }
 
-// GetNodeSet implements Governance interface to return current
+// NodeSet implements Governance interface to return current
 // notary set.
-func (g *Governance) GetNodeSet(_ uint64) (
+func (g *Governance) NodeSet(_ uint64) (
 	ret []crypto.PublicKey) {
 	for _, key := range g.privateKeys {
 		ret = append(ret, key.PublicKey())
@@ -86,8 +86,8 @@ func (g *Governance) GetNodeSet(_ uint64) (
 	return
 }
 
-// GetConfiguration returns the configuration at a given block height.
-func (g *Governance) GetConfiguration(_ uint64) *types.Config {
+// Configuration returns the configuration at a given block height.
+func (g *Governance) Configuration(_ uint64) *types.Config {
 	return &types.Config{
 		NumShards:        1,
 		NumChains:        uint32(len(g.privateKeys)),
@@ -104,8 +104,8 @@ func (g *Governance) GetConfiguration(_ uint64) *types.Config {
 	}
 }
 
-// GetCRS returns the CRS for a given round.
-func (g *Governance) GetCRS(round uint64) common.Hash {
+// CRS returns the CRS for a given round.
+func (g *Governance) CRS(round uint64) common.Hash {
 	return g.crs[round]
 }
 
@@ -114,9 +114,9 @@ func (g *Governance) ProposeCRS(round uint64, signedCRS []byte) {
 	g.crs[round] = crypto.Keccak256Hash(signedCRS)
 }
 
-// GetPrivateKeys return the private key for that node, this function
+// PrivateKeys return the private key for that node, this function
 // is a test utility and not a general Governance interface.
-func (g *Governance) GetPrivateKeys() (keys []crypto.PrivateKey) {
+func (g *Governance) PrivateKeys() (keys []crypto.PrivateKey) {
 	for _, k := range g.privateKeys {
 		keys = append(keys, k)
 	}
diff --git a/core/ticker.go b/core/ticker.go
index eac80de..0d2e433 100644
--- a/core/ticker.go
+++ b/core/ticker.go
@@ -65,11 +65,11 @@ func newTicker(gov Governance, round uint64, tickerType TickerType) (t Ticker) {
 		var duration time.Duration
 		switch tickerType {
 		case TickerBA:
-			duration = gov.GetConfiguration(round).LambdaBA
+			duration = gov.Configuration(round).LambdaBA
 		case TickerDKG:
-			duration = gov.GetConfiguration(round).LambdaDKG
+			duration = gov.Configuration(round).LambdaDKG
 		case TickerCRS:
-			duration = gov.GetConfiguration(round).RoundInterval / 2
+			duration = gov.Configuration(round).RoundInterval / 2
 		}
 		t = newDefaultTicker(duration)
 	}
diff --git a/integration_test/node.go b/integration_test/node.go
index bbd604a..2fa3eb6 100644
--- a/integration_test/node.go
+++ b/integration_test/node.go
@@ -85,10 +85,9 @@ func NewNode(
 	proposingLatency test.LatencyModel) *Node {
 
 	var (
-		shardID          = uint32(0)
 		chainID          = uint32(math.MaxUint32)
-		governanceConfig = gov.GetConfiguration(0)
-		nodeSetKeys      = gov.GetNodeSet(0)
+		governanceConfig = gov.Configuration(0)
+		nodeSetKeys      = gov.NodeSet(0)
 		nodeID           = types.NewNodeID(privateKey.PublicKey())
 	)
 	broadcastTargets := make(map[types.NodeID]struct{})
@@ -116,7 +115,6 @@ func NewNode(
 		app:              app,
 		db:               db,
 		shard: core.NewShard(
-			shardID,
 			governanceConfig,
 			core.NewAuthenticator(privateKey),
 			app,
diff --git a/integration_test/utils.go b/integration_test/utils.go
index 3e33362..6c665ad 100644
--- a/integration_test/utils.go
+++ b/integration_test/utils.go
@@ -25,7 +25,7 @@ func PrepareNodes(
 	if err != nil {
 		return
 	}
-	for _, prvKey := range gov.GetPrivateKeys() {
+	for _, prvKey := range gov.PrivateKeys() {
 		nID := types.NewNodeID(prvKey.PublicKey())
 		apps[nID] = test.NewApp()
 		dbs[nID], err = blockdb.NewMemBackedBlockDB()
diff --git a/simulation/governance.go b/simulation/governance.go
index 8b6c3e5..8a83feb 100644
--- a/simulation/governance.go
+++ b/simulation/governance.go
@@ -78,8 +78,8 @@ func (g *simGovernance) setNetwork(network *network) {
 	g.network = network
 }
 
-// GetNodeSet returns the current notary set.
-func (g *simGovernance) GetNodeSet(round uint64) (ret []crypto.PublicKey) {
+// NodeSet returns the current notary set.
+func (g *simGovernance) NodeSet(round uint64) (ret []crypto.PublicKey) {
 	g.lock.RLock()
 	defer g.lock.RUnlock()
 
@@ -89,8 +89,8 @@ func (g *simGovernance) GetNodeSet(round uint64) (ret []crypto.PublicKey) {
 	return
 }
 
-// GetConfiguration returns the configuration at a given round.
-func (g *simGovernance) GetConfiguration(round uint64) *types.Config {
+// Configuration returns the configuration at a given round.
+func (g *simGovernance) Configuration(round uint64) *types.Config {
 	return &types.Config{
 		NumShards:        1,
 		NumChains:        g.chainNum,
@@ -107,8 +107,8 @@ func (g *simGovernance) GetConfiguration(round uint64) *types.Config {
 	}
 }
 
-// GetCRS returns the CRS for a given round.
-func (g *simGovernance) GetCRS(round uint64) common.Hash {
+// CRS returns the CRS for a given round.
+func (g *simGovernance) CRS(round uint64) common.Hash {
 	return g.crs[round]
 }