diff --git a/action/protocol/context.go b/action/protocol/context.go
index 9b30146b3e..68d74ac010 100644
--- a/action/protocol/context.go
+++ b/action/protocol/context.go
@@ -177,6 +177,7 @@ type (
 		CalculateProbationList   CheckFunc
 		LoadCandidatesLegacy     CheckFunc
 		CandCenterHasAlias       CheckFunc
+		CandidateWithoutIdentity CheckFunc
 	}
 )
 
@@ -391,6 +392,9 @@ func WithFeatureWithHeightCtx(ctx context.Context) context.Context {
 			CandCenterHasAlias: func(height uint64) bool {
 				return !g.IsOkhotsk(height)
 			},
+			CandidateWithoutIdentity: func(height uint64) bool {
+				return !g.IsToBeEnabled(height)
+			},
 		},
 	)
 }
diff --git a/action/protocol/poll/protocol.go b/action/protocol/poll/protocol.go
index f152b1dee1..bd62325146 100644
--- a/action/protocol/poll/protocol.go
+++ b/action/protocol/poll/protocol.go
@@ -129,7 +129,7 @@ func NewProtocol(
 	candidateIndexer *CandidateIndexer,
 	readContract ReadContract,
 	getCandidates GetCandidates,
-	getprobationList GetProbationList,
+	getProbationList GetProbationList,
 	getUnproductiveDelegate GetUnproductiveDelegate,
 	electionCommittee committee.Committee,
 	stakingProto *staking.Protocol,
@@ -155,7 +155,7 @@ func NewProtocol(
 		slasher, err = NewSlasher(
 			productivity,
 			getCandidates,
-			getprobationList,
+			getProbationList,
 			getUnproductiveDelegate,
 			candidateIndexer,
 			genesisConfig.NumCandidateDelegates,
diff --git a/action/protocol/poll/slasher.go b/action/protocol/poll/slasher.go
index 212fad6568..b2c29bb227 100644
--- a/action/protocol/poll/slasher.go
+++ b/action/protocol/poll/slasher.go
@@ -274,7 +274,7 @@ func (sh *Slasher) GetCandidates(ctx context.Context, sr protocol.StateReader, r
 		return nil, uint64(0), errors.Wrapf(err, "failed to get probation list at height %d", targetEpochStartHeight)
 	}
 	// recalculate the voting power for probationlist delegates
-	filteredCandidate, err := filterCandidates(candidates, unqualifiedList, targetEpochStartHeight)
+	filteredCandidate, err := filterCandidates(candidates, unqualifiedList, targetEpochStartHeight, featureWithHeightCtx.CandidateWithoutIdentity(targetEpochStartHeight))
 	if err != nil {
 		return nil, uint64(0), err
 	}
@@ -334,7 +334,7 @@ func (sh *Slasher) GetCandidatesFromIndexer(ctx context.Context, epochStartHeigh
 		return nil, err
 	}
 	// recalculate the voting power for probationlist delegates
-	return filterCandidates(candidates, probationList, epochStartHeight)
+	return filterCandidates(candidates, probationList, epochStartHeight, featureWithHeightCtx.CandidateWithoutIdentity(epochStartHeight))
 }
 
 // GetBPFromIndexer returns BP list from indexer
@@ -520,11 +520,12 @@ func (sh *Slasher) calculateUnproductiveDelegates(ctx context.Context, sr protoc
 	} else {
 		produce[blkCtx.Producer.String()] = 1
 	}
-
+	producerToOwner := make(map[string]string)
 	for _, abp := range delegates {
 		if _, ok := produce[abp.Address]; !ok {
 			produce[abp.Address] = 0
 		}
+		producerToOwner[abp.Address] = abp.Identity
 	}
 	unqualified := make(map[string]uint64, 0)
 	expectedNumBlks := numBlks / uint64(len(produce))
@@ -533,7 +534,18 @@ func (sh *Slasher) calculateUnproductiveDelegates(ctx context.Context, sr protoc
 			unqualified[addr] = expectedNumBlks - actualNumBlks
 		}
 	}
-	return unqualified, nil
+	if protocol.MustGetFeatureWithHeightCtx(ctx).CandidateWithoutIdentity(blkCtx.BlockHeight) {
+		return unqualified, nil
+	}
+	retval := make(map[string]uint64, len(unqualified))
+	for addr, count := range unqualified {
+		if owner, ok := producerToOwner[addr]; ok {
+			retval[owner] = count
+		} else {
+			retval[addr] = count
+		}
+	}
+	return retval, nil
 }
 
 func (sh *Slasher) updateCurrentBlockMeta(ctx context.Context, sm protocol.StateManager) error {
@@ -595,13 +607,18 @@ func filterCandidates(
 	candidates state.CandidateList,
 	unqualifiedList *vote.ProbationList,
 	epochStartHeight uint64,
+	usingOperatorAddr bool,
 ) (state.CandidateList, error) {
 	candidatesMap := make(map[string]*state.Candidate)
 	updatedVotingPower := make(map[string]*big.Int)
 	intensityRate := float64(uint32(100)-unqualifiedList.IntensityRate) / float64(100)
 	for _, cand := range candidates {
 		filterCand := cand.Clone()
-		if _, ok := unqualifiedList.ProbationInfo[cand.Address]; ok {
+		id := cand.Address
+		if !usingOperatorAddr {
+			id = cand.Identity
+		}
+		if _, ok := unqualifiedList.ProbationInfo[id]; ok {
 			// if it is an unqualified delegate, multiply the voting power with probation intensity rate
 			votingPower := new(big.Float).SetInt(filterCand.Votes)
 			filterCand.Votes, _ = votingPower.Mul(votingPower, big.NewFloat(intensityRate)).Int(nil)
diff --git a/action/protocol/rewarding/reward.go b/action/protocol/rewarding/reward.go
index 574bee10b7..be581b65b9 100644
--- a/action/protocol/rewarding/reward.go
+++ b/action/protocol/rewarding/reward.go
@@ -516,12 +516,29 @@ func (p *Protocol) slashDelegate(
 	candidate *state.Candidate,
 	amount *big.Int,
 ) (*action.Log, error) {
-	candidateAddr, err := address.FromString(candidate.Address)
-	if err != nil {
-		return nil, err
-	}
-	if err := stakingProtocol.SlashCandidate(ctx, sm, candidateAddr, amount); err != nil {
-		return nil, errors.Wrapf(err, "failed to slash candidate %s", candidate.Address)
+	var candidateAddr address.Address
+	var err error
+	switch {
+	case protocol.MustGetFeatureCtx(ctx).CandidateSlashByOwner || !protocol.MustGetFeatureWithHeightCtx(ctx).CandidateWithoutIdentity(blockHeight):
+		if candidate.Identity != "" {
+			candidateAddr, err = address.FromString(candidate.Identity)
+			if err != nil {
+				return nil, err
+			}
+			if err := stakingProtocol.SlashCandidateByID(ctx, sm, candidateAddr, amount); err != nil {
+				return nil, errors.Wrapf(err, "failed to slash candidate %s", candidate.Identity)
+			}
+			break
+		}
+		fallthrough
+	default:
+		candidateAddr, err = address.FromString(candidate.Address)
+		if err != nil {
+			return nil, err
+		}
+		if err := stakingProtocol.SlashCandidateByOperator(ctx, sm, candidateAddr, amount); err != nil {
+			return nil, errors.Wrapf(err, "failed to slash candidate %s", candidate.Address)
+		}
 	}
 	data, err := p.encodeRewardLog(rewardingpb.RewardLog_UNPRODUCTIVE_SLASH, candidateAddr.String(), amount)
 	if err != nil {
@@ -558,8 +575,13 @@ func (p *Protocol) slashUqd(
 	slashLogs := make([]*action.Log, 0)
 	snapshot := view.Snapshot()
 	fCtx := protocol.MustGetFeatureCtx(ctx)
+	usingOperator := protocol.MustGetFeatureWithHeightCtx(ctx).CandidateWithoutIdentity(blockHeight)
 	for _, candidate := range candidates {
-		if missed, ok := uqdMap[candidate.Address]; ok {
+		id := candidate.Identity
+		if usingOperator {
+			id = candidate.Address
+		}
+		if missed, ok := uqdMap[id]; ok {
 			if missed == 0 {
 				// hard probation, no slash
 				continue
@@ -571,10 +593,10 @@ func (p *Protocol) slashUqd(
 				slashLogs = append(slashLogs, actLog)
 				totalSlashAmount.Add(totalSlashAmount, amount)
 			case staking.ErrNoSelfStakeBucket:
-				log.S().Errorf("Candidate %s doesn't have self-stake bucket, no slash", candidate.Address)
+				log.S().Errorf("Candidate %s doesn't have self-stake bucket, no slash", id)
 			case staking.ErrCandidateNotExist:
 				if !fCtx.CandidateSlashByOwner {
-					log.S().Errorf("Candidate %s doesn't exist, ignore slash", candidate.Address)
+					log.S().Errorf("Candidate %s doesn't exist, ignore slash", id)
 					continue
 				}
 				fallthrough
diff --git a/action/protocol/staking/candidate.go b/action/protocol/staking/candidate.go
index 19d600f2f4..3017b0daec 100644
--- a/action/protocol/staking/candidate.go
+++ b/action/protocol/staking/candidate.go
@@ -341,14 +341,18 @@ func (d *Candidate) toIoTeXTypes() *iotextypes.CandidateV2 {
 	}
 }
 
-func (d *Candidate) toStateCandidate() *state.Candidate {
-	return &state.Candidate{
+func (d *Candidate) toStateCandidate(ignoreIdentity bool) *state.Candidate {
+	c := &state.Candidate{
 		Address:       d.Operator.String(), // state need candidate operator not owner address
 		Votes:         new(big.Int).Set(d.Votes),
 		RewardAddress: d.Reward.String(),
 		CanName:       []byte(d.Name),
 		BLSPubKey:     d.BLSPubKey,
 	}
+	if !ignoreIdentity {
+		c.Identity = d.GetIdentifier().String()
+	}
+	return c
 }
 
 func (l CandidateList) Len() int      { return len(l) }
@@ -457,10 +461,10 @@ func (l *CandidateList) Decode(keys [][]byte, gvs []systemcontracts.GenericValue
 	return nil
 }
 
-func (l CandidateList) toStateCandidateList() (state.CandidateList, error) {
+func (l CandidateList) toStateCandidateList(ignoreIdentity bool) (state.CandidateList, error) {
 	list := make(state.CandidateList, 0, len(l))
 	for _, c := range l {
-		list = append(list, c.toStateCandidate())
+		list = append(list, c.toStateCandidate(ignoreIdentity))
 	}
 	sort.Sort(list)
 	return list, nil
diff --git a/action/protocol/staking/candidate_center_test.go b/action/protocol/staking/candidate_center_test.go
index 4c192528d9..7a5f495eb7 100644
--- a/action/protocol/staking/candidate_center_test.go
+++ b/action/protocol/staking/candidate_center_test.go
@@ -55,7 +55,7 @@ func testEqualAllCommit(r *require.Assertions, m *CandidateCenter, old Candidate
 	list := m.All()
 	r.Equal(size+increase, len(list))
 	r.Equal(size+increase, m.Size())
-	all, err := list.toStateCandidateList()
+	all, err := list.toStateCandidateList(true)
 	r.NoError(err)
 
 	// number of changed cand = change
@@ -76,7 +76,7 @@ func testEqualAllCommit(r *require.Assertions, m *CandidateCenter, old Candidate
 	list = m.All()
 	r.Equal(size+increase, len(list))
 	r.Equal(size+increase, m.Size())
-	all1, err := list.toStateCandidateList()
+	all1, err := list.toStateCandidateList(true)
 	r.NoError(err)
 	r.Equal(all, all1)
 	return list, nil
diff --git a/action/protocol/staking/candidate_test.go b/action/protocol/staking/candidate_test.go
index 4f480d73f9..b12dba3758 100644
--- a/action/protocol/staking/candidate_test.go
+++ b/action/protocol/staking/candidate_test.go
@@ -62,6 +62,19 @@ func TestSer(t *testing.T) {
 	r.NoError(l1.Deserialize(ser))
 	r.Equal(l, l1)
 
+	sl, err := l.toStateCandidateList(true)
+	r.NoError(err)
+	r.Equal(l.Len(), len(sl))
+	for _, sc := range sl {
+		r.Equal("", sc.Identity)
+	}
+	sl, err = l.toStateCandidateList(false)
+	r.NoError(err)
+	r.Equal(l.Len(), len(sl))
+	for _, sc := range sl {
+		r.NotEqual("", sc.Identity)
+	}
+
 	// empty CandidateList can successfully Serialize/Deserialize
 	var m CandidateList
 	ser, err = m.Serialize()
@@ -102,7 +115,15 @@ func TestClone(t *testing.T) {
 	d.Identifier = identityset.Address(3)
 	r.Equal(d.Identifier, d.GetIdentifier())
 
-	c := d.toStateCandidate()
+	c := d.toStateCandidate(false)
+	r.Equal(d.GetIdentifier().String(), c.Identity)
+	r.Equal(d.Owner.String(), c.Address)
+	r.Equal(d.Reward.String(), c.RewardAddress)
+	r.Equal(d.Votes, c.Votes)
+	r.Equal(d.Name, string(c.CanName))
+
+	c = d.toStateCandidate(true)
+	r.Equal("", c.Identity)
 	r.Equal(d.Owner.String(), c.Address)
 	r.Equal(d.Reward.String(), c.RewardAddress)
 	r.Equal(d.Votes, c.Votes)
diff --git a/action/protocol/staking/protocol.go b/action/protocol/staking/protocol.go
index 53822f8266..252aaca70c 100644
--- a/action/protocol/staking/protocol.go
+++ b/action/protocol/staking/protocol.go
@@ -405,28 +405,43 @@ func (p *Protocol) CreateGenesisStates(
 	return errors.Wrap(csm.Commit(ctx), "failed to commit candidate change in CreateGenesisStates")
 }
 
-func (p *Protocol) SlashCandidate(
+func (p *Protocol) SlashCandidateByOperator(
 	ctx context.Context,
 	sm protocol.StateManager,
 	operator address.Address,
 	amount *big.Int,
 ) error {
-	if amount == nil || amount.Sign() <= 0 {
-		return errors.New("nil or non-positive amount")
+	csm, err := NewCandidateStateManager(sm)
+	if err != nil {
+		return errors.Wrap(err, "failed to create candidate state manager")
 	}
+	return p.slashCandidate(ctx, csm, csm.GetByOperator(operator), amount)
+}
+
+func (p *Protocol) SlashCandidateByID(
+	ctx context.Context,
+	sm protocol.StateManager,
+	id address.Address,
+	amount *big.Int,
+) error {
 	csm, err := NewCandidateStateManager(sm)
 	if err != nil {
 		return errors.Wrap(err, "failed to create candidate state manager")
 	}
-	fCtx := protocol.MustGetFeatureCtx(ctx)
-	var candidate *Candidate
-	if fCtx.CandidateSlashByOwner {
-		candidate = csm.GetByIdentifier(operator)
-	} else {
-		candidate = csm.GetByOperator(operator)
+	return p.slashCandidate(ctx, csm, csm.GetByIdentifier(id), amount)
+}
+
+func (p *Protocol) slashCandidate(
+	ctx context.Context,
+	csm CandidateStateManager,
+	candidate *Candidate,
+	amount *big.Int,
+) error {
+	if amount == nil || amount.Sign() <= 0 {
+		return errors.New("nil or non-positive amount")
 	}
 	if candidate == nil {
-		return errors.Wrapf(ErrCandidateNotExist, "candidate operator %s does not exist", operator.String())
+		return ErrCandidateNotExist
 	}
 	if candidate.SelfStakeBucketIdx == candidateNoSelfStakeBucketIndex {
 		return errors.Wrap(ErrNoSelfStakeBucket, "failed to slash candidate")
@@ -864,7 +879,7 @@ func (p *Protocol) ActiveCandidates(ctx context.Context, sr protocol.StateReader
 			cand = append(cand, list[i])
 		}
 	}
-	return cand.toStateCandidateList()
+	return cand.toStateCandidateList(protocol.MustGetFeatureWithHeightCtx(ctx).CandidateWithoutIdentity(height))
 }
 
 // ReadState read the state on blockchain via protocol
diff --git a/action/protocol/staking/protocol_test.go b/action/protocol/staking/protocol_test.go
index f05a706df5..53943cbb45 100644
--- a/action/protocol/staking/protocol_test.go
+++ b/action/protocol/staking/protocol_test.go
@@ -177,9 +177,9 @@ func TestProtocol(t *testing.T) {
 	}
 
 	// csm's candidate center should be identical to all candidates in stateDB
-	c1, err := all.toStateCandidateList()
+	c1, err := all.toStateCandidateList(true)
 	r.NoError(err)
-	c2, err := csm.DirtyView().candCenter.All().toStateCandidateList()
+	c2, err := csm.DirtyView().candCenter.All().toStateCandidateList(true)
 	r.NoError(err)
 	r.Equal(c1, c2)
 
@@ -669,6 +669,7 @@ func TestSlashCandidate(t *testing.T) {
 		BlockHeight: 100,
 	})
 	ctx = protocol.WithFeatureCtx(ctx)
+	ctx = protocol.WithFeatureWithHeightCtx(ctx)
 
 	t.Run("nil amount", func(t *testing.T) {
 		err := p.SlashCandidate(ctx, sm, owner, nil)
@@ -741,5 +742,10 @@ func TestSlashCandidate(t *testing.T) {
 		)
 		require.NoError(err)
 		require.Equal(1, len(cl))
+		require.Equal(cl[0].Identity, "")
+		cl, err = p.ActiveCandidates(ctx, sm, genesis.Default.ToBeEnabledBlockHeight)
+		require.NoError(err)
+		require.Equal(1, len(cl))
+		require.Equal(cl[0].Identity, owner.String())
 	})
 }
diff --git a/e2etest/contract_staking_v2_test.go b/e2etest/contract_staking_v2_test.go
index c23dccd89c..062c079f60 100644
--- a/e2etest/contract_staking_v2_test.go
+++ b/e2etest/contract_staking_v2_test.go
@@ -2065,6 +2065,7 @@ func checkStakingViewInit(test *e2etest, require *require.Assertions) {
 		BlockTimeStamp: tipHeader.Timestamp(),
 	})
 	ctx = protocol.WithFeatureCtx(ctx)
+	ctx = protocol.WithFeatureWithHeightCtx(ctx)
 	cands, err := stk.ActiveCandidates(ctx, test.cs.StateFactory(), 0)
 	require.NoError(err)
 
@@ -2097,6 +2098,7 @@ func checkStakingVoteView(test *e2etest, require *require.Assertions, candName s
 	})
 	ctx = genesis.WithGenesisContext(ctx, test.cfg.Genesis)
 	ctx = protocol.WithFeatureCtx(ctx)
+	ctx = protocol.WithFeatureWithHeightCtx(ctx)
 	cands, err := stkPtl.ActiveCandidates(ctx, test.cs.StateFactory(), 0)
 	require.NoError(err)
 	cand1 := slices.IndexFunc(cands, func(c *state.Candidate) bool {
diff --git a/go.mod b/go.mod
index 56931316c9..8723c70415 100644
--- a/go.mod
+++ b/go.mod
@@ -30,7 +30,7 @@ require (
 	github.com/iotexproject/iotex-address v0.2.9-0.20251203033311-6e8aa4fd43ef
 	github.com/iotexproject/iotex-antenna-go/v2 v2.6.4
 	github.com/iotexproject/iotex-election v0.3.8-0.20251015031218-8df952babca1
-	github.com/iotexproject/iotex-proto v0.6.5
+	github.com/iotexproject/iotex-proto v0.6.6-0.20251119052518-636e321b7e33
 	github.com/ipfs/go-ipfs-api v0.7.0
 	github.com/libp2p/go-libp2p v0.39.0
 	github.com/mackerelio/go-osstat v0.2.4
diff --git a/go.sum b/go.sum
index d47cf6ec60..73337b0a81 100644
--- a/go.sum
+++ b/go.sum
@@ -668,8 +668,8 @@ github.com/iotexproject/iotex-antenna-go/v2 v2.6.4 h1:7e0VyBDFT+iqwvr/BIk38yf7nC
 github.com/iotexproject/iotex-antenna-go/v2 v2.6.4/go.mod h1:L6AzDHo2TBFDAPA3ly+/PCS4JSX2g3zzhwV8RGQsTDI=
 github.com/iotexproject/iotex-election v0.3.8-0.20251015031218-8df952babca1 h1:jPLni/qKAnxv87HMCutde2tP9JmfWuLZgGpB4OArQGM=
 github.com/iotexproject/iotex-election v0.3.8-0.20251015031218-8df952babca1/go.mod h1:w9HriT1coMRbuknaSD2xqiOqDTnowBDzvFZv8tg1j2M=
-github.com/iotexproject/iotex-proto v0.6.5 h1:EyzwDXYtGWvJ/qnYCwhqypOjpEAQPvESo+EdPcUJPE0=
-github.com/iotexproject/iotex-proto v0.6.5/go.mod h1:OOXZIG6Q9tInog8Y5zzEJQsDv9IaG/xxpDtl4KzdWZs=
+github.com/iotexproject/iotex-proto v0.6.6-0.20251119052518-636e321b7e33 h1:zMcBndFDAbu0eutHEP2VuaeSZ53HXvc4BwOnhn2YvYk=
+github.com/iotexproject/iotex-proto v0.6.6-0.20251119052518-636e321b7e33/go.mod h1:OOXZIG6Q9tInog8Y5zzEJQsDv9IaG/xxpDtl4KzdWZs=
 github.com/ipfs/boxo v0.27.2 h1:sGo4KdwBaMjdBjH08lqPJyt27Z4CO6sugne3ryX513s=
 github.com/ipfs/boxo v0.27.2/go.mod h1:qEIRrGNr0bitDedTCzyzBHxzNWqYmyuHgK8LG9Q83EM=
 github.com/ipfs/go-block-format v0.2.0 h1:ZqrkxBA2ICbDRbK8KJs/u0O3dlp6gmAuuXUJNiW1Ycs=
diff --git a/state/candidate.go b/state/candidate.go
index 8ba4fa1da8..af4484757c 100644
--- a/state/candidate.go
+++ b/state/candidate.go
@@ -35,7 +35,8 @@ var (
 type (
 	// Candidate indicates the structure of a candidate
 	Candidate struct {
-		Address       string
+		Identity      string // Candidate Identity
+		Address       string // Operator address
 		Votes         *big.Int
 		RewardAddress string
 		CanName       []byte // used as identifier to merge with native staking result, not part of protobuf
@@ -57,7 +58,8 @@ func (c *Candidate) Equal(d *Candidate) bool {
 	if c == nil || d == nil {
 		return false
 	}
-	return strings.Compare(c.Address, d.Address) == 0 &&
+	return strings.Compare(c.Identity, d.Identity) == 0 &&
+		strings.Compare(c.Address, d.Address) == 0 &&
 		c.RewardAddress == d.RewardAddress &&
 		c.Votes.Cmp(d.Votes) == 0 &&
 		bytes.Equal(c.BLSPubKey, d.BLSPubKey)
@@ -76,6 +78,7 @@ func (c *Candidate) Clone() *Candidate {
 		copy(pubkey, c.BLSPubKey)
 	}
 	return &Candidate{
+		Identity:      c.Identity,
 		Address:       c.Address,
 		Votes:         new(big.Int).Set(c.Votes),
 		RewardAddress: c.RewardAddress,
@@ -198,6 +201,7 @@ func (l *CandidateList) Decode(suffixs [][]byte, values []systemcontracts.Generi
 // candidateToPb converts a candidate to protobuf's candidate message
 func candidateToPb(cand *Candidate) *iotextypes.Candidate {
 	candidatePb := &iotextypes.Candidate{
+		Identity:      cand.Identity,
 		Address:       cand.Address,
 		Votes:         cand.Votes.Bytes(),
 		RewardAddress: cand.RewardAddress,
@@ -217,6 +221,7 @@ func pbToCandidate(candPb *iotextypes.Candidate) (*Candidate, error) {
 		return nil, errors.Wrap(ErrCandidatePb, "protobuf's candidate message cannot be nil")
 	}
 	candidate := &Candidate{
+		Identity:      candPb.Identity,
 		Address:       candPb.Address,
 		Votes:         big.NewInt(0).SetBytes(candPb.Votes),
 		RewardAddress: candPb.RewardAddress,