mse/mse.go | 26 +++++++++++++++++++-------

diff --git a/mse/mse.go b/mse/mse.go
index 02f649a6dc76c7c35ce0e73cc2e6539a06350a61..421ade3fcba6813fee2bf5113264c6044bb30d5f 100644
--- a/mse/mse.go
+++ b/mse/mse.go
@@ -116,16 +116,28 @@
 type cipherWriter struct {
 	c *rc4.Cipher
 	w io.Writer
+	b []byte
 }
 
 func (cr *cipherWriter) Write(b []byte) (n int, err error) {
-	be := make([]byte, len(b))
-	cr.c.XORKeyStream(be, b)
-	n, err = cr.w.Write(be)
-	if n != len(be) {
+	be := func() []byte {
+		if len(cr.b) < len(b) {
+			return make([]byte, len(b))
+		} else {
+			ret := cr.b
+			cr.b = nil
+			return ret
+		}
+	}()
+	cr.c.XORKeyStream(be[:], b)
+	n, err = cr.w.Write(be[:len(b)])
+	if n != len(b) {
 		// The cipher will have advanced beyond the callers stream position.
 		// We can't use the cipher anymore.
 		cr.c = nil
+	}
+	if len(be) > len(cr.b) {
+		cr.b = be
 	}
 	return
 }
@@ -390,7 +402,7 @@ 	_, err = io.CopyN(ioutil.Discard, r, int64(padLen))
 	if err != nil {
 		return
 	}
-	ret = readWriter{r, &cipherWriter{e, h.conn}}
+	ret = readWriter{r, &cipherWriter{e, h.conn, nil}}
 	return
 }
 
@@ -449,7 +461,7 @@ 		h.ia = make([]byte, lenIA)
 		unmarshal(r, h.ia)
 	}
 	buf := &bytes.Buffer{}
-	w := cipherWriter{h.newEncrypt(false), buf}
+	w := cipherWriter{h.newEncrypt(false), buf, nil}
 	padLen = uint16(newPadLen())
 	err = marshal(&w, &vc, uint32(cryptoMethodRC4), padLen, zeroPad[:padLen])
 	if err != nil {
@@ -459,7 +471,7 @@ 	err = h.postWrite(buf.Bytes())
 	if err != nil {
 		return
 	}
-	ret = readWriter{io.MultiReader(bytes.NewReader(h.ia), r), &cipherWriter{w.c, h.conn}}
+	ret = readWriter{io.MultiReader(bytes.NewReader(h.ia), r), &cipherWriter{w.c, h.conn, nil}}
 	return
 }