diff --git a/chat/sign/sign.go b/chat/sign/sign.go
index 220ba36..1074698 100644
--- a/chat/sign/sign.go
+++ b/chat/sign/sign.go
@@ -52,6 +52,16 @@ func (m *MessageHeader) ReadFrom(r io.Reader) (n int64, err error) {
 	return n + n3, err
 }
 
+func (m *MessageHeader) Hash(bodyHash []byte) []byte {
+	hash := sha256.New()
+	if m.PrevSignature != nil {
+		hash.Write(m.PrevSignature)
+	}
+	hash.Write(m.Sender[:])
+	hash.Write(bodyHash)
+	return hash.Sum(nil)
+}
+
 type MessageBody struct {
 	PlainMsg     string
 	DecoratedMsg json.RawMessage
@@ -182,6 +192,10 @@ func (msg *PlayerMessage) WriteTo(w io.Writer) (n int64, err error) {
 	}.WriteTo(w)
 }
 
+func (msg *PlayerMessage) Hash() []byte {
+	return msg.MessageHeader.Hash(msg.MessageBody.Hash())
+}
+
 func genSalt() (salt int64) {
 	err := binary.Read(rand.Reader, binary.BigEndian, &salt)
 	if err != nil {
diff --git a/data/packetid/packetid.go b/data/packetid/packetid.go
index b5db1ae..f799818 100644
--- a/data/packetid/packetid.go
+++ b/data/packetid/packetid.go
@@ -145,6 +145,7 @@ const (
 	ClientboundUpdateMobEffect
 	ClientboundUpdateRecipes
 	ClientboundUpdateTags
+	ClientboundPacketIDGuard
 )
 
 // Game Serverbound
@@ -200,4 +201,5 @@ const (
 	ServerboundTeleportToEntity
 	ServerboundUseItemOn
 	ServerboundUseItem
+	ServerboundPacketIDGuard
 )