diff --git a/cmd/tendermint/commands/lite.go b/cmd/tendermint/commands/lite.go
index edad4fbb..150371d6 100644
--- a/cmd/tendermint/commands/lite.go
+++ b/cmd/tendermint/commands/lite.go
@@ -30,6 +30,7 @@ var (
 	nodeAddr   string
 	chainID    string
 	home       string
+	cacheSize  int
 )
 
 func init() {
@@ -37,6 +38,7 @@ func init() {
 	LiteCmd.Flags().StringVar(&nodeAddr, "node", "tcp://localhost:26657", "Connect to a Tendermint node at this address")
 	LiteCmd.Flags().StringVar(&chainID, "chain-id", "tendermint", "Specify the Tendermint chain ID")
 	LiteCmd.Flags().StringVar(&home, "home-dir", ".tendermint-lite", "Specify the home directory")
+	LiteCmd.Flags().IntVar(&cacheSize, "cache-size", 10, "Specify the memory trust store cache size")
 }
 
 func ensureAddrHasSchemeOrDefaultToTCP(addr string) (string, error) {
@@ -69,7 +71,7 @@ func runProxy(cmd *cobra.Command, args []string) error {
 	node := rpcclient.NewHTTP(nodeAddr, "/websocket")
 
 	logger.Info("Constructing Verifier...")
-	cert, err := proxy.NewVerifier(chainID, home, node, logger)
+	cert, err := proxy.NewVerifier(chainID, home, node, logger, cacheSize)
 	if err != nil {
 		return cmn.ErrorWrap(err, "constructing Verifier")
 	}
diff --git a/lite/base_verifier.go b/lite/base_verifier.go
index e60d3953..fcde01c0 100644
--- a/lite/base_verifier.go
+++ b/lite/base_verifier.go
@@ -12,7 +12,7 @@ var _ Verifier = (*BaseVerifier)(nil)
 
 // BaseVerifier lets us check the validity of SignedHeaders at height or
 // later, requiring sufficient votes (> 2/3) from the given valset.
-// To certify blocks produced by a blockchain with mutable validator sets,
+// To verify blocks produced by a blockchain with mutable validator sets,
 // use the DynamicVerifier.
 // TODO: Handle unbonding time.
 type BaseVerifier struct {
@@ -40,15 +40,15 @@ func (bc *BaseVerifier) ChainID() string {
 }
 
 // Implements Verifier.
-func (bc *BaseVerifier) Certify(signedHeader types.SignedHeader) error {
+func (bc *BaseVerifier) Verify(signedHeader types.SignedHeader) error {
 
-	// We can't certify commits older than bc.height.
+	// We can't verify commits older than bc.height.
 	if signedHeader.Height < bc.height {
-		return cmn.NewError("BaseVerifier height is %v, cannot certify height %v",
+		return cmn.NewError("BaseVerifier height is %v, cannot verify height %v",
 			bc.height, signedHeader.Height)
 	}
 
-	// We can't certify with the wrong validator set.
+	// We can't verify with the wrong validator set.
 	if !bytes.Equal(signedHeader.ValidatorsHash,
 		bc.valset.Hash()) {
 		return lerr.ErrUnexpectedValidators(signedHeader.ValidatorsHash, bc.valset.Hash())
@@ -57,7 +57,7 @@ func (bc *BaseVerifier) Certify(signedHeader types.SignedHeader) error {
 	// Do basic sanity checks.
 	err := signedHeader.ValidateBasic(bc.chainID)
 	if err != nil {
-		return cmn.ErrorWrap(err, "in certify")
+		return cmn.ErrorWrap(err, "in verify")
 	}
 
 	// Check commit signatures.
@@ -65,7 +65,7 @@ func (bc *BaseVerifier) Certify(signedHeader types.SignedHeader) error {
 		bc.chainID, signedHeader.Commit.BlockID,
 		signedHeader.Height, signedHeader.Commit)
 	if err != nil {
-		return cmn.ErrorWrap(err, "in certify")
+		return cmn.ErrorWrap(err, "in verify")
 	}
 
 	return nil
diff --git a/lite/base_verifier_test.go b/lite/base_verifier_test.go
index dab7885f..2ef1203f 100644
--- a/lite/base_verifier_test.go
+++ b/lite/base_verifier_test.go
@@ -43,7 +43,7 @@ func TestBaseCert(t *testing.T) {
 	for _, tc := range cases {
 		sh := tc.keys.GenSignedHeader(chainID, tc.height, nil, tc.vals, tc.vals,
 			[]byte("foo"), []byte("params"), []byte("results"), tc.first, tc.last)
-		err := cert.Certify(sh)
+		err := cert.Verify(sh)
 		if tc.proper {
 			assert.Nil(err, "%+v", err)
 		} else {
diff --git a/lite/doc.go b/lite/doc.go
index 59f77056..2a0ba23e 100644
--- a/lite/doc.go
+++ b/lite/doc.go
@@ -54,11 +54,11 @@ validator set, and that the height of the commit is at least height (or
 greater).
 
 SignedHeader.Commit may be signed by a different validator set, it can get
-certified with a BaseVerifier as long as sufficient signatures from the
+verified with a BaseVerifier as long as sufficient signatures from the
 previous validator set are present in the commit.
 
 DynamicVerifier - this Verifier implements an auto-update and persistence
-strategy to certify any SignedHeader of the blockchain.
+strategy to verify any SignedHeader of the blockchain.
 
 ## Provider and PersistentProvider
 
diff --git a/lite/dynamic_verifier.go b/lite/dynamic_verifier.go
index 3d1a70f2..2dee69f9 100644
--- a/lite/dynamic_verifier.go
+++ b/lite/dynamic_verifier.go
@@ -2,12 +2,15 @@ package lite
 
 import (
 	"bytes"
-
+	"fmt"
+	"sync"
 	log "github.com/tendermint/tendermint/libs/log"
 	lerr "github.com/tendermint/tendermint/lite/errors"
 	"github.com/tendermint/tendermint/types"
 )
 
+const sizeOfPendingMap = 1024
+
 var _ Verifier = (*DynamicVerifier)(nil)
 
 // DynamicVerifier implements an auto-updating Verifier.  It uses a
@@ -21,6 +24,11 @@ type DynamicVerifier struct {
 	trusted PersistentProvider
 	// This is a source of new info, like a node rpc, or other import method.
 	source Provider
+
+	// pending map for synchronize concurrent verification requests
+	pendingVerifications map[int64]chan struct{}
+
+	mtx sync.Mutex
 }
 
 // NewDynamicVerifier returns a new DynamicVerifier. It uses the
@@ -31,10 +39,11 @@ type DynamicVerifier struct {
 // files.Provider.  The source provider should be a client.HTTPProvider.
 func NewDynamicVerifier(chainID string, trusted PersistentProvider, source Provider) *DynamicVerifier {
 	return &DynamicVerifier{
-		logger:  log.NewNopLogger(),
-		chainID: chainID,
-		trusted: trusted,
-		source:  source,
+		logger:               log.NewNopLogger(),
+		chainID:              chainID,
+		trusted:              trusted,
+		source:               source,
+		pendingVerifications: make(map[int64]chan struct{}, sizeOfPendingMap),
 	}
 }
 
@@ -56,7 +65,40 @@ func (ic *DynamicVerifier) ChainID() string {
 // ic.trusted and ic.source to prove the new validators.  On success, it will
 // try to store the SignedHeader in ic.trusted if the next
 // validator can be sourced.
-func (ic *DynamicVerifier) Certify(shdr types.SignedHeader) error {
+func (ic *DynamicVerifier) Verify(shdr types.SignedHeader) error {
+
+	// Performs synchronization for multi-threads verification at the same height.
+	ic.mtx.Lock()
+	if pending := ic.pendingVerifications[shdr.Height]; pending != nil {
+		ic.mtx.Unlock()
+		<-pending // pending is chan struct{}
+	} else {
+		pending := make(chan struct{})
+		ic.pendingVerifications[shdr.Height] = pending
+		defer func() {
+			close(pending)
+			ic.mtx.Lock()
+			delete(ic.pendingVerifications, shdr.Height)
+			ic.mtx.Unlock()
+		}()
+		ic.mtx.Unlock()
+	}
+	//Get the exact trusted commit for h, and if it is
+	// equal to shdr, then don't even verify it,
+	// and just return nil.
+	trustedFCSameHeight, err := ic.trusted.LatestFullCommit(ic.chainID, shdr.Height, shdr.Height)
+	if err == nil {
+		// If loading trust commit successfully, and trust commit equal to shdr, then don't verify it,
+		// just return nil.
+		if bytes.Equal(trustedFCSameHeight.SignedHeader.Hash(), shdr.Hash()) {
+			ic.logger.Info(fmt.Sprintf("Load full commit at height %d from cache, there is not need to verify.", shdr.Height))
+			return nil
+		}
+	} else if !lerr.IsErrCommitNotFound(err) {
+		// Return error if it is not CommitNotFound error
+		ic.logger.Info(fmt.Sprintf("Encountered unknown error in loading full commit at height %d.", shdr.Height))
+		return err
+	}
 
 	// Get the latest known full commit <= h-1 from our trusted providers.
 	// The full commit at h-1 contains the valset to sign for h.
@@ -94,9 +136,9 @@ func (ic *DynamicVerifier) Certify(shdr types.SignedHeader) error {
 		}
 	}
 
-	// Certify the signed header using the matching valset.
+	// Verify the signed header using the matching valset.
 	cert := NewBaseVerifier(ic.chainID, trustedFC.Height()+1, trustedFC.NextValidators)
-	err = cert.Certify(shdr)
+	err = cert.Verify(shdr)
 	if err != nil {
 		return err
 	}
diff --git a/lite/dynamic_verifier_test.go b/lite/dynamic_verifier_test.go
index 74e2d55a..401c1487 100644
--- a/lite/dynamic_verifier_test.go
+++ b/lite/dynamic_verifier_test.go
@@ -2,8 +2,8 @@ package lite
 
 import (
 	"fmt"
+	"sync"
 	"testing"
-
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 
@@ -49,7 +49,7 @@ func TestInquirerValidPath(t *testing.T) {
 
 	// This should fail validation:
 	sh := fcz[count-1].SignedHeader
-	err = cert.Certify(sh)
+	err = cert.Verify(sh)
 	require.NotNil(err)
 
 	// Adding a few commits in the middle should be insufficient.
@@ -57,7 +57,7 @@ func TestInquirerValidPath(t *testing.T) {
 		err := source.SaveFullCommit(fcz[i])
 		require.Nil(err)
 	}
-	err = cert.Certify(sh)
+	err = cert.Verify(sh)
 	assert.NotNil(err)
 
 	// With more info, we succeed.
@@ -65,7 +65,7 @@ func TestInquirerValidPath(t *testing.T) {
 		err := source.SaveFullCommit(fcz[i])
 		require.Nil(err)
 	}
-	err = cert.Certify(sh)
+	err = cert.Verify(sh)
 	assert.Nil(err, "%+v", err)
 }
 
@@ -115,18 +115,18 @@ func TestInquirerVerifyHistorical(t *testing.T) {
 	err = source.SaveFullCommit(fcz[7])
 	require.Nil(err, "%+v", err)
 	sh := fcz[8].SignedHeader
-	err = cert.Certify(sh)
+	err = cert.Verify(sh)
 	require.Nil(err, "%+v", err)
 	assert.Equal(fcz[7].Height(), cert.LastTrustedHeight())
 	fc_, err := trust.LatestFullCommit(chainID, fcz[8].Height(), fcz[8].Height())
 	require.NotNil(err, "%+v", err)
 	assert.Equal(fc_, (FullCommit{}))
 
-	// With fcz[9] Certify will update last trusted height.
+	// With fcz[9] Verify will update last trusted height.
 	err = source.SaveFullCommit(fcz[9])
 	require.Nil(err, "%+v", err)
 	sh = fcz[8].SignedHeader
-	err = cert.Certify(sh)
+	err = cert.Verify(sh)
 	require.Nil(err, "%+v", err)
 	assert.Equal(fcz[8].Height(), cert.LastTrustedHeight())
 	fc_, err = trust.LatestFullCommit(chainID, fcz[8].Height(), fcz[8].Height())
@@ -141,13 +141,70 @@ func TestInquirerVerifyHistorical(t *testing.T) {
 
 	// Try to check an unknown seed in the past.
 	sh = fcz[3].SignedHeader
-	err = cert.Certify(sh)
+	err = cert.Verify(sh)
 	require.Nil(err, "%+v", err)
 	assert.Equal(fcz[8].Height(), cert.LastTrustedHeight())
 
 	// Jump all the way forward again.
 	sh = fcz[count-1].SignedHeader
-	err = cert.Certify(sh)
+	err = cert.Verify(sh)
 	require.Nil(err, "%+v", err)
 	assert.Equal(fcz[9].Height(), cert.LastTrustedHeight())
 }
+
+func TestConcurrencyInquirerVerify(t *testing.T) {
+	_, require := assert.New(t), require.New(t)
+	trust := NewDBProvider("trust", dbm.NewMemDB()).SetLimit(10)
+	source := NewDBProvider("source", dbm.NewMemDB())
+
+	// Set up the validators to generate test blocks.
+	var vote int64 = 10
+	keys := genPrivKeys(5)
+	nkeys := keys.Extend(1)
+
+	// Construct a bunch of commits, each with one more height than the last.
+	chainID := "inquiry-test"
+	count := 10
+	consHash := []byte("special-params")
+	fcz := make([]FullCommit, count)
+	for i := 0; i < count; i++ {
+		vals := keys.ToValidators(vote, 0)
+		nextVals := nkeys.ToValidators(vote, 0)
+		h := int64(1 + i)
+		appHash := []byte(fmt.Sprintf("h=%d", h))
+		resHash := []byte(fmt.Sprintf("res=%d", h))
+		fcz[i] = keys.GenFullCommit(
+			chainID, h, nil,
+			vals, nextVals,
+			appHash, consHash, resHash, 0, len(keys))
+		// Extend the keys by 1 each time.
+		keys = nkeys
+		nkeys = nkeys.Extend(1)
+	}
+
+	// Initialize a Verifier with the initial state.
+	err := trust.SaveFullCommit(fcz[0])
+	require.Nil(err)
+	cert := NewDynamicVerifier(chainID, trust, source)
+	cert.SetLogger(log.TestingLogger())
+
+	err = source.SaveFullCommit(fcz[7])
+	err = source.SaveFullCommit(fcz[8])
+	require.Nil(err, "%+v", err)
+	sh := fcz[8].SignedHeader
+
+	var wg sync.WaitGroup
+	count = 100
+	errList := make([]error, count)
+	for i := 0; i < count; i++ {
+		wg.Add(1)
+		go func(index int) {
+			errList[index] = cert.Verify(sh)
+			defer wg.Done()
+		}(i)
+	}
+	wg.Wait()
+	for _, err := range errList {
+		require.Nil(err)
+	}
+}
diff --git a/lite/proxy/query.go b/lite/proxy/query.go
index 6f5a2899..84ff98b4 100644
--- a/lite/proxy/query.go
+++ b/lite/proxy/query.go
@@ -146,7 +146,7 @@ func GetCertifiedCommit(h int64, client rpcclient.Client, cert lite.Verifier) (t
 			h, sh.Height)
 	}
 
-	if err = cert.Certify(sh); err != nil {
+	if err = cert.Verify(sh); err != nil {
 		return types.SignedHeader{}, err
 	}
 
diff --git a/lite/proxy/verifier.go b/lite/proxy/verifier.go
index a93d30c7..b7c11f18 100644
--- a/lite/proxy/verifier.go
+++ b/lite/proxy/verifier.go
@@ -8,12 +8,12 @@ import (
 	lclient "github.com/tendermint/tendermint/lite/client"
 )
 
-func NewVerifier(chainID, rootDir string, client lclient.SignStatusClient, logger log.Logger) (*lite.DynamicVerifier, error) {
+func NewVerifier(chainID, rootDir string, client lclient.SignStatusClient, logger log.Logger, cacheSize int) (*lite.DynamicVerifier, error) {
 
 	logger = logger.With("module", "lite/proxy")
 	logger.Info("lite/proxy/NewVerifier()...", "chainID", chainID, "rootDir", rootDir, "client", client)
 
-	memProvider := lite.NewDBProvider("trusted.mem", dbm.NewMemDB()).SetLimit(10)
+	memProvider := lite.NewDBProvider("trusted.mem", dbm.NewMemDB()).SetLimit(cacheSize)
 	lvlProvider := lite.NewDBProvider("trusted.lvl", dbm.NewDB("trust-base", dbm.LevelDBBackend, rootDir))
 	trust := lite.NewMultiProvider(
 		memProvider,
diff --git a/lite/proxy/wrapper.go b/lite/proxy/wrapper.go
index 522511a8..4c0df022 100644
--- a/lite/proxy/wrapper.go
+++ b/lite/proxy/wrapper.go
@@ -134,10 +134,10 @@ func (w Wrapper) Commit(height *int64) (*ctypes.ResultCommit, error) {
 	}
 	rpcclient.WaitForHeight(w.Client, *height, nil)
 	res, err := w.Client.Commit(height)
-	// if we got it, then certify it
+	// if we got it, then verify it
 	if err == nil {
 		sh := res.SignedHeader
-		err = w.cert.Certify(sh)
+		err = w.cert.Verify(sh)
 	}
 	return res, err
 }
diff --git a/lite/types.go b/lite/types.go
index 7228c74a..643f5ad4 100644
--- a/lite/types.go
+++ b/lite/types.go
@@ -8,6 +8,6 @@ import (
 // Verifier must know the current or recent set of validitors by some other
 // means.
 type Verifier interface {
-	Certify(sheader types.SignedHeader) error
+	Verify(sheader types.SignedHeader) error
 	ChainID() string
 }