diff --git a/dht_test.go b/dht_test.go
index 74eb52724..76331951f 100644
--- a/dht_test.go
+++ b/dht_test.go
@@ -1910,3 +1910,51 @@ func TestProtocolUpgrade(t *testing.T) {
 		t.Fatalf("Expected 'buzz' got '%s'", string(value))
 	}
 }
+
+func TestInvalidKeys(t *testing.T) {
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	nDHTs := 2
+	dhts := setupDHTS(t, ctx, nDHTs)
+	defer func() {
+		for i := 0; i < nDHTs; i++ {
+			dhts[i].Close()
+			defer dhts[i].host.Close()
+		}
+	}()
+
+	t.Logf("connecting %d dhts in a ring", nDHTs)
+	for i := 0; i < nDHTs; i++ {
+		connect(t, ctx, dhts[i], dhts[(i+1)%len(dhts)])
+	}
+
+	querier := dhts[0]
+	_, err := querier.GetClosestPeers(ctx, "")
+	if err == nil {
+		t.Fatal("get closest peers should have failed")
+	}
+
+	_, err = querier.FindProviders(ctx, cid.Cid{})
+	switch err {
+	case routing.ErrNotFound, routing.ErrNotSupported, kb.ErrLookupFailure:
+		t.Fatal("failed with the wrong error: ", err)
+	case nil:
+		t.Fatal("find providers should have failed")
+	}
+
+	_, err = querier.FindPeer(ctx, peer.ID(""))
+	if err != peer.ErrEmptyPeerID {
+		t.Fatal("expected to fail due to the empty peer ID")
+	}
+
+	_, err = querier.GetValue(ctx, "")
+	if err == nil {
+		t.Fatal("expected to have failed")
+	}
+
+	err = querier.PutValue(ctx, "", []byte("foobar"))
+	if err == nil {
+		t.Fatal("expected to have failed")
+	}
+}
diff --git a/handlers.go b/handlers.go
index 42445b70f..3dc709792 100644
--- a/handlers.go
+++ b/handlers.go
@@ -52,16 +52,15 @@ func (dht *IpfsDHT) handlerForMsgType(t pb.Message_MessageType) dhtHandler {
 }
 
 func (dht *IpfsDHT) handleGetValue(ctx context.Context, p peer.ID, pmes *pb.Message) (_ *pb.Message, err error) {
-	// setup response
-	resp := pb.NewMessage(pmes.GetType(), pmes.GetKey(), pmes.GetClusterLevel())
-
 	// first, is there even a key?
 	k := pmes.GetKey()
 	if len(k) == 0 {
 		return nil, errors.New("handleGetValue but no key was provided")
-		// TODO: send back an error response? could be bad, but the other node's hanging.
 	}
 
+	// setup response
+	resp := pb.NewMessage(pmes.GetType(), pmes.GetKey(), pmes.GetClusterLevel())
+
 	rec, err := dht.checkLocalDatastore(k)
 	if err != nil {
 		return nil, err
@@ -150,6 +149,10 @@ func cleanRecord(rec *recpb.Record) {
 
 // Store a value in this peer local storage
 func (dht *IpfsDHT) handlePutValue(ctx context.Context, p peer.ID, pmes *pb.Message) (_ *pb.Message, err error) {
+	if len(pmes.GetKey()) == 0 {
+		return nil, errors.New("handleGetValue but no key was provided")
+	}
+
 	rec := pmes.GetRecord()
 	if rec == nil {
 		logger.Debugw("got nil record from", "from", p)
@@ -253,6 +256,10 @@ func (dht *IpfsDHT) handleFindPeer(ctx context.Context, from peer.ID, pmes *pb.M
 	resp := pb.NewMessage(pmes.GetType(), nil, pmes.GetClusterLevel())
 	var closest []peer.ID
 
+	if len(pmes.GetKey()) == 0 {
+		return nil, fmt.Errorf("handleFindPeer with empty key")
+	}
+
 	// if looking for self... special case where we send it on CloserPeers.
 	targetPid := peer.ID(pmes.GetKey())
 	if targetPid == dht.self {
@@ -300,12 +307,15 @@ func (dht *IpfsDHT) handleFindPeer(ctx context.Context, from peer.ID, pmes *pb.M
 }
 
 func (dht *IpfsDHT) handleGetProviders(ctx context.Context, p peer.ID, pmes *pb.Message) (_ *pb.Message, _err error) {
-	resp := pb.NewMessage(pmes.GetType(), pmes.GetKey(), pmes.GetClusterLevel())
 	key := pmes.GetKey()
 	if len(key) > 80 {
 		return nil, fmt.Errorf("handleGetProviders key size too large")
+	} else if len(key) == 0 {
+		return nil, fmt.Errorf("handleGetProviders key is empty")
 	}
 
+	resp := pb.NewMessage(pmes.GetType(), pmes.GetKey(), pmes.GetClusterLevel())
+
 	// check if we have this value, to add ourselves as provider.
 	has, err := dht.datastore.Has(convertToDsKey(key))
 	if err != nil && err != ds.ErrNotFound {
@@ -341,7 +351,9 @@ func (dht *IpfsDHT) handleGetProviders(ctx context.Context, p peer.ID, pmes *pb.
 func (dht *IpfsDHT) handleAddProvider(ctx context.Context, p peer.ID, pmes *pb.Message) (_ *pb.Message, _err error) {
 	key := pmes.GetKey()
 	if len(key) > 80 {
-		return nil, fmt.Errorf("handleAddProviders key size too large")
+		return nil, fmt.Errorf("handleAddProvider key size too large")
+	} else if len(key) == 0 {
+		return nil, fmt.Errorf("handleAddProvider key is empty")
 	}
 
 	logger.Debugf("adding provider", "from", p, "key", key)
diff --git a/handlers_test.go b/handlers_test.go
index 6e098f815..d88fdac1f 100644
--- a/handlers_test.go
+++ b/handlers_test.go
@@ -67,6 +67,27 @@ func TestCleanRecord(t *testing.T) {
 	}
 }
 
+func TestBadMessage(t *testing.T) {
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	dht := setupDHT(ctx, t, false)
+
+	for _, typ := range []pb.Message_MessageType{
+		pb.Message_PUT_VALUE, pb.Message_GET_VALUE, pb.Message_ADD_PROVIDER,
+		pb.Message_GET_PROVIDERS, pb.Message_FIND_NODE,
+	} {
+		msg := &pb.Message{
+			Type: typ,
+			// explicitly avoid the key.
+		}
+		_, err := dht.handlerForMsgType(typ)(ctx, dht.Host().ID(), msg)
+		if err == nil {
+			t.Fatalf("expected processing message to fail for type %s", pb.Message_FIND_NODE)
+		}
+	}
+}
+
 func BenchmarkHandleFindPeer(b *testing.B) {
 	ctx, cancel := context.WithCancel(context.Background())
 	defer cancel()
diff --git a/lookup.go b/lookup.go
index a602a9a8f..a696df4cf 100644
--- a/lookup.go
+++ b/lookup.go
@@ -72,6 +72,9 @@ func (lk loggableKeyBytes) String() string {
 // If the context is canceled, this function will return the context error along
 // with the closest K peers it has found so far.
 func (dht *IpfsDHT) GetClosestPeers(ctx context.Context, key string) (<-chan peer.ID, error) {
+	if key == "" {
+		return nil, fmt.Errorf("can't lookup empty key")
+	}
 	//TODO: I can break the interface! return []peer.ID
 	lookupRes, err := dht.runLookupWithFollowup(ctx, key,
 		func(ctx context.Context, p peer.ID) ([]*peer.AddrInfo, error) {
diff --git a/pb/message.go b/pb/message.go
index a7e9d14f2..3023d6438 100644
--- a/pb/message.go
+++ b/pb/message.go
@@ -5,7 +5,6 @@ import (
 	"github.com/libp2p/go-libp2p-core/peer"
 
 	logging "github.com/ipfs/go-log"
-	b58 "github.com/mr-tron/base58/base58"
 	ma "github.com/multiformats/go-multiaddr"
 )
 
@@ -138,16 +137,6 @@ func (m *Message) SetClusterLevel(level int) {
 	m.ClusterLevelRaw = lvl + 1
 }
 
-// Loggable turns a Message into machine-readable log output
-func (m *Message) Loggable() map[string]interface{} {
-	return map[string]interface{}{
-		"message": map[string]string{
-			"type": m.Type.String(),
-			"key":  b58.Encode([]byte(m.GetKey())),
-		},
-	}
-}
-
 // ConnectionType returns a Message_ConnectionType associated with the
 // network.Connectedness.
 func ConnectionType(c network.Connectedness) Message_ConnectionType {
diff --git a/routing.go b/routing.go
index 8ae8180b5..6808284a1 100644
--- a/routing.go
+++ b/routing.go
@@ -394,6 +394,8 @@ func (dht *IpfsDHT) refreshRTIfNoShortcut(key kb.ID, lookupRes *lookupWithFollow
 func (dht *IpfsDHT) Provide(ctx context.Context, key cid.Cid, brdcst bool) (err error) {
 	if !dht.enableProviders {
 		return routing.ErrNotSupported
+	} else if !key.Defined() {
+		return fmt.Errorf("invalid cid: undefined")
 	}
 	logger.Debugw("finding provider", "cid", key)
 
@@ -486,7 +488,10 @@ func (dht *IpfsDHT) makeProvRecord(key []byte) (*pb.Message, error) {
 func (dht *IpfsDHT) FindProviders(ctx context.Context, c cid.Cid) ([]peer.AddrInfo, error) {
 	if !dht.enableProviders {
 		return nil, routing.ErrNotSupported
+	} else if !c.Defined() {
+		return nil, fmt.Errorf("invalid cid: undefined")
 	}
+
 	var providers []peer.AddrInfo
 	for p := range dht.FindProvidersAsync(ctx, c, dht.bucketSize) {
 		providers = append(providers, p)
@@ -500,7 +505,7 @@ func (dht *IpfsDHT) FindProviders(ctx context.Context, c cid.Cid) ([]peer.AddrIn
 // completes. Note: not reading from the returned channel may block the query
 // from progressing.
 func (dht *IpfsDHT) FindProvidersAsync(ctx context.Context, key cid.Cid, count int) <-chan peer.AddrInfo {
-	if !dht.enableProviders {
+	if !dht.enableProviders || !key.Defined() {
 		peerOut := make(chan peer.AddrInfo)
 		close(peerOut)
 		return peerOut
@@ -613,6 +618,10 @@ func (dht *IpfsDHT) findProvidersAsyncRoutine(ctx context.Context, key multihash
 
 // FindPeer searches for a peer with given ID.
 func (dht *IpfsDHT) FindPeer(ctx context.Context, id peer.ID) (_ peer.AddrInfo, err error) {
+	if err := id.Validate(); err != nil {
+		return peer.AddrInfo{}, err
+	}
+
 	logger.Debugw("finding peer", "peer", id)
 
 	// Check if were already connected to them