diff --git a/waku/v2/protocol/relay/validators.go b/waku/v2/protocol/relay/validators.go
index ed145fdf..6e99fd36 100644
--- a/waku/v2/protocol/relay/validators.go
+++ b/waku/v2/protocol/relay/validators.go
@@ -4,7 +4,9 @@ import (
 	"context"
 	"crypto/ecdsa"
 	"crypto/elliptic"
+	"encoding/binary"
 	"encoding/hex"
+	"time"
 
 	"github.com/ethereum/go-ethereum/crypto"
 	"github.com/ethereum/go-ethereum/crypto/secp256k1"
@@ -13,19 +15,46 @@ import (
 	"github.com/libp2p/go-libp2p/core/peer"
 	"github.com/waku-org/go-waku/waku/v2/hash"
 	"github.com/waku-org/go-waku/waku/v2/protocol/pb"
+	"github.com/waku-org/go-waku/waku/v2/timesource"
 	"go.uber.org/zap"
 	proto "google.golang.org/protobuf/proto"
 )
 
 // Application level message hash
 func MsgHash(pubSubTopic string, msg *pb.WakuMessage) []byte {
-	// TODO: Other fields?
-	return hash.SHA256([]byte(pubSubTopic), msg.Payload, []byte(msg.ContentTopic))
+	timestampBytes := make([]byte, 8)
+	binary.LittleEndian.PutUint64(timestampBytes, uint64(msg.Timestamp))
+
+	var ephemeralByte byte
+	if msg.Ephemeral {
+		ephemeralByte = 1
+	}
+
+	return hash.SHA256(
+		[]byte(pubSubTopic),
+		msg.Payload,
+		[]byte(msg.ContentTopic),
+		timestampBytes,
+		[]byte{ephemeralByte},
+	)
+}
+
+const MessageWindowDuration = time.Minute * 5
+
+func withinTimeWindow(t timesource.Timesource, msg *pb.WakuMessage) bool {
+	if msg.Timestamp == 0 {
+		return false
+	}
+
+	now := t.Now()
+	msgTime := time.Unix(0, msg.Timestamp)
+
+	return now.Sub(msgTime).Abs() <= MessageWindowDuration
 }
 
 type validatorFn = func(ctx context.Context, peerID peer.ID, message *pubsub.Message) bool
 
-func validatorFnBuilder(topic string, publicKey *ecdsa.PublicKey) validatorFn {
+func validatorFnBuilder(t timesource.Timesource, topic string, publicKey *ecdsa.PublicKey) validatorFn {
 	pubkBytes := crypto.FromECDSAPub(publicKey)
 	return func(ctx context.Context, peerID peer.ID, message *pubsub.Message) bool {
 		msg := new(pb.WakuMessage)
@@ -34,6 +63,10 @@ func validatorFnBuilder(topic string, publicKey *ecdsa.PublicKey) validatorFn {
 			return false
 		}
 
+		if !withinTimeWindow(t, msg) {
+			return false
+		}
+
 		msgHash := MsgHash(topic, msg)
 		signature := msg.Meta
 
@@ -43,7 +76,7 @@ func validatorFnBuilder(topic string, publicKey *ecdsa.PublicKey) validatorFn {
 
 func (w *WakuRelay) AddSignedTopicValidator(topic string, publicKey *ecdsa.PublicKey) error {
 	w.log.Info("adding validator to signed topic", zap.String("topic", topic), zap.String("publicKey", hex.EncodeToString(elliptic.Marshal(publicKey.Curve, publicKey.X, publicKey.Y))))
-	err := w.pubsub.RegisterTopicValidator(topic, validatorFnBuilder(topic, publicKey))
+	err := w.pubsub.RegisterTopicValidator(topic, validatorFnBuilder(w.timesource, topic, publicKey))
 	if err != nil {
 		return err
 	}
diff --git a/waku/v2/protocol/relay/validators_test.go b/waku/v2/protocol/relay/validators_test.go
index 8f2bff5b..6377d6b7 100644
--- a/waku/v2/protocol/relay/validators_test.go
+++ b/waku/v2/protocol/relay/validators_test.go
@@ -5,17 +5,38 @@ import (
 	"context"
 	"encoding/hex"
 	"testing"
+	"time"
 
 	"github.com/ethereum/go-ethereum/crypto"
 	pubsub "github.com/libp2p/go-libp2p-pubsub"
 	pubsub_pb "github.com/libp2p/go-libp2p-pubsub/pb"
 	"github.com/stretchr/testify/require"
 	"github.com/waku-org/go-waku/waku/v2/protocol/pb"
-	"github.com/waku-org/go-waku/waku/v2/timesource"
-	"github.com/waku-org/go-waku/waku/v2/utils"
 	"google.golang.org/protobuf/proto"
 )
 
+type FakeTimesource struct {
+	now time.Time
+}
+
+func NewFakeTimesource(now time.Time) FakeTimesource {
+	return FakeTimesource{now}
+}
+
+func (f FakeTimesource) Start(ctx context.Context) error {
+	return nil
+}
+
+func (f FakeTimesource) Stop() {}
+
+func (f FakeTimesource) Now() time.Time {
+	return f.now
+}
+
+type Timesource interface {
+	Now() time.Time
+}
+
 func TestMsgHash(t *testing.T) {
 	privKeyB, _ := hex.DecodeString("5526a8990317c9b7b58d07843d270f9cd1d9aaee129294c1c478abf7261dd9e6")
 	prvKey, _ := crypto.ToECDSA(privKeyB)
@@ -23,31 +44,52 @@ func TestMsgHash(t *testing.T) {
 	payload, _ := hex.DecodeString("1A12E077D0E89F9CAC11FBBB6A676C86120B5AD3E248B1F180E98F15EE43D2DFCF62F00C92737B2FF6F59B3ABA02773314B991C41DC19ADB0AD8C17C8E26757B")
 	contentTopic := "content-topic"
 	pubsubTopic := "pubsub-topic"
+	ephemeral := true
+	timestamp := time.Unix(0, 1683208172339052800)
 
 	msg := &pb.WakuMessage{
 		Payload:      payload,
 		ContentTopic: contentTopic,
-		Timestamp:    utils.GetUnixEpoch(timesource.NewDefaultClock()),
+		Timestamp:    timestamp.UnixNano(),
+		Ephemeral:    ephemeral,
 	}
 
 	err := SignMessage(prvKey, pubsubTopic, msg)
 	require.NoError(t, err)
 
-	expectedSignature, _ := hex.DecodeString("B139487797A242291E0DD3F689777E559FB749D565D55FF202C18E24F21312A555043437B4F808BB0D21D542D703873DC712D76A3BAF1C5C8FF754210D894AD4")
+	expectedSignature, _ := hex.DecodeString("127FA211B2514F0E974A055392946DC1A14052182A6ABEFB8A6CD7C51DA1BF2E40595D28EF1A9488797C297EED3AAC45430005FB3A7F037BDD9FC4BD99F59E63")
 	require.True(t, bytes.Equal(expectedSignature, msg.Meta))
 
 	msgData, _ := proto.Marshal(msg)
 
-	expectedMessageHash, _ := hex.DecodeString("0914369D6D0C13783A8E86409FE42C68D8E8296456B9A9468C845006BCE5B9B2")
+	expectedMessageHash, _ := hex.DecodeString("662F8C20A335F170BD60ABC1F02AD66F0C6A6EE285DA2A53C95259E7937C0AE9")
 	messageHash := MsgHash(pubsubTopic, msg)
 	require.True(t, bytes.Equal(expectedMessageHash, messageHash))
 
-	myValidator := validatorFnBuilder(pubsubTopic, &prvKey.PublicKey)
-
+	myValidator := validatorFnBuilder(NewFakeTimesource(timestamp), pubsubTopic, &prvKey.PublicKey)
 	result := myValidator(context.Background(), "", &pubsub.Message{
 		Message: &pubsub_pb.Message{
 			Data: msgData,
 		},
 	})
 	require.True(t, result)
+
+	// Exceed 5m window in both directions
+	now5m1sInPast := timestamp.Add(-5 * time.Minute).Add(-1 * time.Minute)
+	myValidator = validatorFnBuilder(NewFakeTimesource(now5m1sInPast), pubsubTopic, &prvKey.PublicKey)
+	result = myValidator(context.Background(), "", &pubsub.Message{
+		Message: &pubsub_pb.Message{
+			Data: msgData,
+		},
+	})
+	require.False(t, result)
+
+	now5m1sInFuture := timestamp.Add(5 * time.Minute).Add(1 * time.Minute)
+	myValidator = validatorFnBuilder(NewFakeTimesource(now5m1sInFuture), pubsubTopic, &prvKey.PublicKey)
+	result = myValidator(context.Background(), "", &pubsub.Message{
+		Message: &pubsub_pb.Message{
+			Data: msgData,
+		},
+	})
+	require.False(t, result)
 }