diff --git a/consensus/istanbul/backend.go b/consensus/istanbul/backend.go
new file mode 100644
index 0000000000..46039438e7
--- /dev/null
+++ b/consensus/istanbul/backend.go
@@ -0,0 +1,73 @@
+// Copyright 2017 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum 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 go-ethereum 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 go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package istanbul
+
+import (
+	"math/big"
+	"time"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/event"
+)
+
+// Backend provides application specific functions for Istanbul core
+type Backend interface {
+	// Address returns the owner's address
+	Address() common.Address
+
+	// Validators returns the validator set
+	Validators(proposal Proposal) ValidatorSet
+
+	// EventMux returns the event mux in backend
+	EventMux() *event.TypeMux
+
+	// Broadcast sends a message to all validators (include self)
+	Broadcast(valSet ValidatorSet, payload []byte) error
+
+	// Gossip sends a message to all validators (exclude self)
+	Gossip(valSet ValidatorSet, payload []byte) error
+
+	// Commit delivers an approved proposal to backend.
+	// The delivered proposal will be put into blockchain.
+	Commit(proposal Proposal, seals [][]byte) error
+
+	// Verify verifies the proposal. If a consensus.ErrFutureBlock error is returned,
+	// the time difference of the proposal and current time is also returned.
+	Verify(Proposal) (time.Duration, error)
+
+	// Sign signs input data with the backend's private key
+	Sign([]byte) ([]byte, error)
+
+	// CheckSignature verifies the signature by checking if it's signed by
+	// the given validator
+	CheckSignature(data []byte, addr common.Address, sig []byte) error
+
+	// LastProposal retrieves latest committed proposal and the address of proposer
+	LastProposal() (Proposal, common.Address)
+
+	// HasPropsal checks if the combination of the given hash and height matches any existing blocks
+	HasPropsal(hash common.Hash, number *big.Int) bool
+
+	// GetProposer returns the proposer of the given block height
+	GetProposer(number uint64) common.Address
+
+	// ParentValidators returns the validator set of the given proposal's parent block
+	ParentValidators(proposal Proposal) ValidatorSet
+
+	// HasBadBlock returns whether the block with the hash is a bad block
+	HasBadProposal(hash common.Hash) bool
+}
diff --git a/consensus/istanbul/config.go b/consensus/istanbul/config.go
index e6cb762604..d2d44bf2e8 100644
--- a/consensus/istanbul/config.go
+++ b/consensus/istanbul/config.go
@@ -24,17 +24,15 @@ const (
 )
 
 type Config struct {
-	RequestTimeout uint64         `toml:",omitempty"` // The timeout for each Istanbul round in milliseconds. This timeout should be larger than BlockPauseTime.
+	RequestTimeout uint64         `toml:",omitempty"` // The timeout for each Istanbul round in milliseconds.
 	BlockPeriod    uint64         `toml:",omitempty"` // Default minimum difference between two consecutive block's timestamps in second
-	BlockPauseTime uint64         `toml:",omitempty"` // Pause time when zero tx in previous block, values should be larger than istanbul_block_period
-	ProposerPolicy ProposerPolicy `toml:",omitempty"` // The policy for proposer, the detail is not determined
+	ProposerPolicy ProposerPolicy `toml:",omitempty"` // The policy for proposer selection
 	Epoch          uint64         `toml:",omitempty"` // The number of blocks after which to checkpoint and reset the pending votes
 }
 
 var DefaultConfig = &Config{
 	RequestTimeout: 10000,
 	BlockPeriod:    1,
-	BlockPauseTime: 2,
 	ProposerPolicy: RoundRobin,
 	Epoch:          30000,
 }
diff --git a/consensus/istanbul/errors.go b/consensus/istanbul/errors.go
new file mode 100644
index 0000000000..ed5b62342f
--- /dev/null
+++ b/consensus/istanbul/errors.go
@@ -0,0 +1,29 @@
+// Copyright 2017 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum 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 go-ethereum 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 go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package istanbul
+
+import "errors"
+
+var (
+	// ErrUnauthorizedAddress is returned when given address cannot be found in
+	// current validator set.
+	ErrUnauthorizedAddress = errors.New("unauthorized address")
+	// ErrStoppedEngine is returned if the engine is stopped
+	ErrStoppedEngine = errors.New("stopped engine")
+	// ErrStartedEngine is returned if the engine is already started
+	ErrStartedEngine = errors.New("started engine")
+)
diff --git a/consensus/istanbul/events.go b/consensus/istanbul/events.go
new file mode 100644
index 0000000000..fb6e5bd9c2
--- /dev/null
+++ b/consensus/istanbul/events.go
@@ -0,0 +1,31 @@
+// Copyright 2017 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum 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 go-ethereum 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 go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package istanbul
+
+// RequestEvent is posted to propose a proposal
+type RequestEvent struct {
+	Proposal Proposal
+}
+
+// MessageEvent is posted for Istanbul engine communication
+type MessageEvent struct {
+	Payload []byte
+}
+
+// FinalCommittedEvent is posted when a proposal is committed
+type FinalCommittedEvent struct {
+}
diff --git a/consensus/istanbul/types.go b/consensus/istanbul/types.go
new file mode 100644
index 0000000000..86b586a2d0
--- /dev/null
+++ b/consensus/istanbul/types.go
@@ -0,0 +1,147 @@
+// Copyright 2017 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum 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 go-ethereum 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 go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package istanbul
+
+import (
+	"fmt"
+	"io"
+	"math/big"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/rlp"
+)
+
+// Proposal supports retrieving height and serialized block to be used during Istanbul consensus.
+type Proposal interface {
+	// Number retrieves the sequence number of this proposal.
+	Number() *big.Int
+
+	// Hash retrieves the hash of this proposal.
+	Hash() common.Hash
+
+	EncodeRLP(w io.Writer) error
+
+	DecodeRLP(s *rlp.Stream) error
+
+	String() string
+}
+
+type Request struct {
+	Proposal Proposal
+}
+
+// View includes a round number and a sequence number.
+// Sequence is the block number we'd like to commit.
+// Each round has a number and is composed by 3 steps: preprepare, prepare and commit.
+//
+// If the given block is not accepted by validators, a round change will occur
+// and the validators start a new round with round+1.
+type View struct {
+	Round    *big.Int
+	Sequence *big.Int
+}
+
+// EncodeRLP serializes b into the Ethereum RLP format.
+func (v *View) EncodeRLP(w io.Writer) error {
+	return rlp.Encode(w, []interface{}{v.Round, v.Sequence})
+}
+
+// DecodeRLP implements rlp.Decoder, and load the consensus fields from a RLP stream.
+func (v *View) DecodeRLP(s *rlp.Stream) error {
+	var view struct {
+		Round    *big.Int
+		Sequence *big.Int
+	}
+
+	if err := s.Decode(&view); err != nil {
+		return err
+	}
+	v.Round, v.Sequence = view.Round, view.Sequence
+	return nil
+}
+
+func (v *View) String() string {
+	return fmt.Sprintf("{Round: %d, Sequence: %d}", v.Round.Uint64(), v.Sequence.Uint64())
+}
+
+// Cmp compares v and y and returns:
+//   -1 if v <  y
+//    0 if v == y
+//   +1 if v >  y
+func (v *View) Cmp(y *View) int {
+	if v.Sequence.Cmp(y.Sequence) != 0 {
+		return v.Sequence.Cmp(y.Sequence)
+	}
+	if v.Round.Cmp(y.Round) != 0 {
+		return v.Round.Cmp(y.Round)
+	}
+	return 0
+}
+
+type Preprepare struct {
+	View     *View
+	Proposal Proposal
+}
+
+// EncodeRLP serializes b into the Ethereum RLP format.
+func (b *Preprepare) EncodeRLP(w io.Writer) error {
+	return rlp.Encode(w, []interface{}{b.View, b.Proposal})
+}
+
+// DecodeRLP implements rlp.Decoder, and load the consensus fields from a RLP stream.
+func (b *Preprepare) DecodeRLP(s *rlp.Stream) error {
+	var preprepare struct {
+		View     *View
+		Proposal *types.Block
+	}
+
+	if err := s.Decode(&preprepare); err != nil {
+		return err
+	}
+	b.View, b.Proposal = preprepare.View, preprepare.Proposal
+
+	return nil
+}
+
+type Subject struct {
+	View   *View
+	Digest common.Hash
+}
+
+// EncodeRLP serializes b into the Ethereum RLP format.
+func (b *Subject) EncodeRLP(w io.Writer) error {
+	return rlp.Encode(w, []interface{}{b.View, b.Digest})
+}
+
+// DecodeRLP implements rlp.Decoder, and load the consensus fields from a RLP stream.
+func (b *Subject) DecodeRLP(s *rlp.Stream) error {
+	var subject struct {
+		View   *View
+		Digest common.Hash
+	}
+
+	if err := s.Decode(&subject); err != nil {
+		return err
+	}
+	b.View, b.Digest = subject.View, subject.Digest
+	return nil
+}
+
+func (b *Subject) String() string {
+	return fmt.Sprintf("{View: %v, Digest: %v}", b.View, b.Digest.String())
+}
diff --git a/consensus/istanbul/types_test.go b/consensus/istanbul/types_test.go
new file mode 100644
index 0000000000..cc23d486f1
--- /dev/null
+++ b/consensus/istanbul/types_test.go
@@ -0,0 +1,71 @@
+// Copyright 2017 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum 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 go-ethereum 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 go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package istanbul
+
+import (
+	"math/big"
+	"testing"
+)
+
+func TestViewCompare(t *testing.T) {
+	// test equality
+	srvView := &View{
+		Sequence: big.NewInt(2),
+		Round:    big.NewInt(1),
+	}
+	tarView := &View{
+		Sequence: big.NewInt(2),
+		Round:    big.NewInt(1),
+	}
+	if r := srvView.Cmp(tarView); r != 0 {
+		t.Errorf("source(%v) should be equal to target(%v): have %v, want %v", srvView, tarView, r, 0)
+	}
+
+	// test larger Sequence
+	tarView = &View{
+		Sequence: big.NewInt(1),
+		Round:    big.NewInt(1),
+	}
+	if r := srvView.Cmp(tarView); r != 1 {
+		t.Errorf("source(%v) should be larger than target(%v): have %v, want %v", srvView, tarView, r, 1)
+	}
+
+	// test larger Round
+	tarView = &View{
+		Sequence: big.NewInt(2),
+		Round:    big.NewInt(0),
+	}
+	if r := srvView.Cmp(tarView); r != 1 {
+		t.Errorf("source(%v) should be larger than target(%v): have %v, want %v", srvView, tarView, r, 1)
+	}
+
+	// test smaller Sequence
+	tarView = &View{
+		Sequence: big.NewInt(3),
+		Round:    big.NewInt(1),
+	}
+	if r := srvView.Cmp(tarView); r != -1 {
+		t.Errorf("source(%v) should be smaller than target(%v): have %v, want %v", srvView, tarView, r, -1)
+	}
+	tarView = &View{
+		Sequence: big.NewInt(2),
+		Round:    big.NewInt(2),
+	}
+	if r := srvView.Cmp(tarView); r != -1 {
+		t.Errorf("source(%v) should be smaller than target(%v): have %v, want %v", srvView, tarView, r, -1)
+	}
+}
diff --git a/consensus/istanbul/utils.go b/consensus/istanbul/utils.go
new file mode 100644
index 0000000000..22137b4148
--- /dev/null
+++ b/consensus/istanbul/utils.go
@@ -0,0 +1,60 @@
+// Copyright 2017 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum 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 go-ethereum 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 go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package istanbul
+
+import (
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/crypto"
+	"github.com/ethereum/go-ethereum/crypto/sha3"
+	"github.com/ethereum/go-ethereum/log"
+	"github.com/ethereum/go-ethereum/rlp"
+)
+
+func RLPHash(v interface{}) (h common.Hash) {
+	hw := sha3.NewKeccak256()
+	rlp.Encode(hw, v)
+	hw.Sum(h[:0])
+	return h
+}
+
+// GetSignatureAddress gets the signer address from the signature
+func GetSignatureAddress(data []byte, sig []byte) (common.Address, error) {
+	// 1. Keccak data
+	hashData := crypto.Keccak256(data)
+	// 2. Recover public key
+	pubkey, err := crypto.SigToPub(hashData, sig)
+	if err != nil {
+		return common.Address{}, err
+	}
+	return crypto.PubkeyToAddress(*pubkey), nil
+}
+
+func CheckValidatorSignature(valSet ValidatorSet, data []byte, sig []byte) (common.Address, error) {
+	// 1. Get signature address
+	signer, err := GetSignatureAddress(data, sig)
+	if err != nil {
+		log.Error("Failed to get signer address", "err", err)
+		return common.Address{}, err
+	}
+
+	// 2. Check validator
+	if _, val := valSet.GetByAddress(signer); val != nil {
+		return val.Address(), nil
+	}
+
+	return common.Address{}, ErrUnauthorizedAddress
+}
diff --git a/consensus/istanbul/validator.go b/consensus/istanbul/validator.go
new file mode 100644
index 0000000000..e0d142866e
--- /dev/null
+++ b/consensus/istanbul/validator.go
@@ -0,0 +1,80 @@
+// Copyright 2017 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum 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 go-ethereum 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 go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package istanbul
+
+import (
+	"strings"
+
+	"github.com/ethereum/go-ethereum/common"
+)
+
+type Validator interface {
+	// Address returns address
+	Address() common.Address
+
+	// String representation of Validator
+	String() string
+}
+
+// ----------------------------------------------------------------------------
+
+type Validators []Validator
+
+func (slice Validators) Len() int {
+	return len(slice)
+}
+
+func (slice Validators) Less(i, j int) bool {
+	return strings.Compare(slice[i].String(), slice[j].String()) < 0
+}
+
+func (slice Validators) Swap(i, j int) {
+	slice[i], slice[j] = slice[j], slice[i]
+}
+
+// ----------------------------------------------------------------------------
+
+type ValidatorSet interface {
+	// Calculate the proposer
+	CalcProposer(lastProposer common.Address, round uint64)
+	// Return the validator size
+	Size() int
+	// Return the validator array
+	List() []Validator
+	// Get validator by index
+	GetByIndex(i uint64) Validator
+	// Get validator by given address
+	GetByAddress(addr common.Address) (int, Validator)
+	// Get current proposer
+	GetProposer() Validator
+	// Check whether the validator with given address is a proposer
+	IsProposer(address common.Address) bool
+	// Add validator
+	AddValidator(address common.Address) bool
+	// Remove validator
+	RemoveValidator(address common.Address) bool
+	// Copy validator set
+	Copy() ValidatorSet
+	// Get the maximum number of faulty nodes
+	F() int
+	// Get proposer policy
+	Policy() ProposerPolicy
+}
+
+// ----------------------------------------------------------------------------
+
+type ProposalSelector func(ValidatorSet, common.Address, uint64) Validator