diff --git a/midgen.go b/midgen.go
new file mode 100644
index 00000000..03293294
--- /dev/null
+++ b/midgen.go
@@ -0,0 +1,32 @@
+package pubsub
+
+import "sync"
+
+type msgIDGenerator struct {
+	defGen MsgIdFunction
+
+	topicGens    map[string]MsgIdFunction
+	topicGensLk sync.RWMutex
+}
+
+func (m *msgIDGenerator) Add(topic string, gen MsgIdFunction) {
+	m.topicGensLk.Lock()
+	m.topicGens[topic] = gen
+	m.topicGensLk.Unlock()
+}
+
+func (m *msgIDGenerator) GenID(msg *Message) string {
+	if msg.ID != "" {
+		return msg.ID
+	}
+
+	m.topicGensLk.RLock()
+	gen, ok := m.topicGens[msg.GetTopic()]
+	m.topicGensLk.RUnlock()
+	if !ok {
+		gen = m.defGen
+	}
+
+	msg.ID = gen(msg.Message)
+	return msg.ID
+}
diff --git a/pubsub.go b/pubsub.go
index fdfa755b..cba16c59 100644
--- a/pubsub.go
+++ b/pubsub.go
@@ -213,6 +213,7 @@ const (
 
 type Message struct {
 	*pb.Message
+	ID string
 	ReceivedFrom  peer.ID
 	ValidatorData interface{}
 }
@@ -1047,8 +1048,7 @@ func (p *PubSub) handleIncomingRPC(rpc *RPC) {
 				continue
 			}
 
-			msg := &Message{pmsg, rpc.from, nil}
-			p.pushMsg(msg)
+			p.pushMsg(&Message{pmsg, "", rpc.from, nil})
 		}
 	}
 
diff --git a/topic.go b/topic.go
index 8de88c3c..edec94ff 100644
--- a/topic.go
+++ b/topic.go
@@ -283,7 +283,7 @@ func (t *Topic) Publish(ctx context.Context, data []byte, opts ...PubOpt) error
 		}
 	}
 
-	return t.p.val.PushLocal(&Message{m, t.p.host.ID(), nil})
+	return t.p.val.PushLocal(&Message{m, "", t.p.host.ID(), nil})
 }
 
 // WithReadiness returns a publishing option for only publishing when the router is ready.