diff --git a/ratchet/ratchet.go b/ratchet/ratchet.go
index a6c26f2..833d87c 100644
--- a/ratchet/ratchet.go
+++ b/ratchet/ratchet.go
@@ -238,17 +238,20 @@ func (r *Ratchet) CompleteKeyExchange(kx *KeyExchange, alice bool) error {
 }
 
 // Encrypt acts like append() but appends an encrypted version of msg to out.
-func (r *Ratchet) Encrypt(out, msg []byte) []byte {
+func (r *Ratchet) Encrypt(out, msg []byte) ([]byte, error) {
 	if r.ratchet {
 		r.randBytes(r.sendRatchetPrivate[:])
 		copy(r.sendHeaderKey[:], r.nextSendHeaderKey[:])
 
-		var sharedKey, keyMaterial [32]byte
-		curve25519.ScalarMult(&sharedKey, &r.sendRatchetPrivate, &r.recvRatchetPublic)
+		var keyMaterial [32]byte
+		sharedKey, err := curve25519.X25519(r.sendRatchetPrivate[:], r.recvRatchetPublic[:])
+		if err != nil {
+			return nil, err
+		}
 		sha := sha256.New()
 		sha.Write(rootKeyUpdateLabel)
 		sha.Write(r.rootKey[:])
-		sha.Write(sharedKey[:])
+		sha.Write(sharedKey)
 		sha.Sum(keyMaterial[:0])
 		h := hmac.New(sha256.New, keyMaterial[:])
 		deriveKey(&r.rootKey, rootKeyLabel, h)
@@ -277,7 +280,7 @@ func (r *Ratchet) Encrypt(out, msg []byte) []byte {
 	out = append(out, headerNonce[:]...)
 	out = secretbox.Seal(out, header[:], &headerNonce, &r.sendHeaderKey)
 	r.sendCount++
-	return secretbox.Seal(out, msg, &messageNonce, &messageKey)
+	return secretbox.Seal(out, msg, &messageNonce, &messageKey), nil
 }
 
 // trySavedKeys tries to decrypt ciphertext using keys saved for missing messages.
@@ -458,15 +461,17 @@ func (r *Ratchet) Decrypt(ciphertext []byte) ([]byte, error) {
 		return nil, err
 	}
 
-	var dhPublic, sharedKey, rootKey, chainKey, keyMaterial [32]byte
+	var dhPublic, rootKey, chainKey, keyMaterial [32]byte
 	copy(dhPublic[:], header[8:])
 
-	curve25519.ScalarMult(&sharedKey, &r.sendRatchetPrivate, &dhPublic)
-
+	sharedKey, err := curve25519.X25519(r.sendRatchetPrivate[:], dhPublic[:])
+	if err != nil {
+		return nil, err
+	}
 	sha := sha256.New()
 	sha.Write(rootKeyUpdateLabel)
 	sha.Write(r.rootKey[:])
-	sha.Write(sharedKey[:])
+	sha.Write(sharedKey)
 
 	var rootKeyHMAC hash.Hash
 
diff --git a/ratchet/ratchet_test.go b/ratchet/ratchet_test.go
index d97ef7d..c3dbb8c 100644
--- a/ratchet/ratchet_test.go
+++ b/ratchet/ratchet_test.go
@@ -97,7 +97,10 @@ func TestExchange(t *testing.T) {
 	a, b := pairedRatchet(t)
 
 	msg := []byte(strings.Repeat("test message", 1024*1024))
-	encrypted := a.Encrypt(nil, msg)
+	encrypted, err := a.Encrypt(nil, msg)
+	if err != nil {
+		t.Fatal(err)
+	}
 	result, err := b.Decrypt(encrypted)
 	if err != nil {
 		t.Fatal(err)
@@ -163,8 +166,10 @@ func testScript(t *testing.T, script []scriptAction) {
 
 			var msg [20]byte
 			rand.Reader.Read(msg[:])
-			encrypted := sender.Encrypt(nil, msg[:])
-
+			encrypted, err := sender.Encrypt(nil, msg[:])
+			if err != nil {
+				t.Fatalf("Encrypt: %v", err)
+			}
 			switch action.result {
 			case deliver:
 				result, err := receiver.Decrypt(encrypted)
@@ -339,7 +344,10 @@ func TestDiskState(t *testing.T) {
 	a, b := pairedRatchet(t)
 
 	msg := []byte("test message")
-	encrypted := a.Encrypt(nil, msg)
+	encrypted, err := a.Encrypt(nil, msg)
+	if err != nil {
+		t.Fatal(err)
+	}
 	result, err := b.Decrypt(encrypted)
 	if err != nil {
 		t.Fatal(err)
@@ -348,7 +356,10 @@ func TestDiskState(t *testing.T) {
 		t.Fatalf("result doesn't match: %x vs %x", msg, result)
 	}
 
-	encrypted = b.Encrypt(nil, msg)
+	encrypted, err = b.Encrypt(nil, msg)
+	if err != nil {
+		t.Fatal(err)
+	}
 	result, err = a.Decrypt(encrypted)
 	if err != nil {
 		t.Fatal(err)
@@ -414,7 +425,10 @@ func TestDiskState(t *testing.T) {
 	}
 
 	// send message to alice
-	encrypted = newBob.Encrypt(nil, msg)
+	encrypted, err = newBob.Encrypt(nil, msg)
+	if err != nil {
+		t.Fatal(err)
+	}
 	result, err = newAlice.Decrypt(encrypted)
 	if err != nil {
 		t.Fatal(err)
@@ -423,7 +437,10 @@ func TestDiskState(t *testing.T) {
 		t.Fatalf("result doesn't match: %x vs %x", msg, result)
 	}
 
-	encrypted = newAlice.Encrypt(nil, msg)
+	encrypted, err = newAlice.Encrypt(nil, msg)
+	if err != nil {
+		t.Fatal(err)
+	}
 	result, err = newBob.Decrypt(encrypted)
 	if err != nil {
 		t.Fatal(err)
diff --git a/zkclient/msg.go b/zkclient/msg.go
index 9abfc23..ddd06cf 100644
--- a/zkclient/msg.go
+++ b/zkclient/msg.go
@@ -415,9 +415,7 @@ func (z *ZKC) crpc(r *ratchet.Ratchet, payload interface{}) ([]byte, error) {
 	bb.Write(p)
 
 	// encrypt CRPC
-	blob := r.Encrypt(nil, bb.Bytes())
-
-	return blob, nil
+	return r.Encrypt(nil, bb.Bytes())
 }
 
 func (z *ZKC) pm(id [zkidentity.IdentitySize]byte, message string, mode rpc.MessageMode) error {
diff --git a/zkidentity/zkidentity_test.go b/zkidentity/zkidentity_test.go
index 4b8fece..64404f2 100644
--- a/zkidentity/zkidentity_test.go
+++ b/zkidentity/zkidentity_test.go
@@ -78,7 +78,10 @@ func TestEncryptDecryptSmall(t *testing.T) {
 	a, b := pairedRatchet()
 
 	msg := []byte("test message")
-	encrypted := a.Encrypt(nil, msg)
+	encrypted, err := a.Encrypt(nil, msg)
+	if err != nil {
+		t.Fatal(err)
+	}
 	result, err := b.Decrypt(encrypted)
 	if err != nil {
 		t.Fatal(err)
@@ -124,7 +127,10 @@ func TestEncryptDecryptLarge(t *testing.T) {
 	a, b := pairedRatchet()
 
 	msg := []byte(strings.Repeat("test message", 1024*1024))
-	encrypted := a.Encrypt(nil, msg)
+	encrypted, err := a.Encrypt(nil, msg)
+	if err != nil {
+		t.Fatal(err)
+	}
 	result, err := b.Decrypt(encrypted)
 	if err != nil {
 		t.Fatal(err)