diff --git a/crypto/ext4crypt/KeyBuffer.cpp b/crypto/ext4crypt/KeyBuffer.cpp
new file mode 100644
index 0000000..e7aede5
--- /dev/null
+++ b/crypto/ext4crypt/KeyBuffer.cpp
@@ -0,0 +1,37 @@
+/*
+ * Copyright (C) 2017 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "KeyBuffer.h"
+
+#include <algorithm>
+#include <cstring>
+
+namespace android {
+namespace vold {
+
+KeyBuffer operator+(KeyBuffer&& lhs, const KeyBuffer& rhs) {
+    std::copy(rhs.begin(), rhs.end(), std::back_inserter(lhs));
+    return std::move(lhs);
+}
+
+KeyBuffer operator+(KeyBuffer&& lhs, const char* rhs) {
+    std::copy(rhs, rhs + strlen(rhs), std::back_inserter(lhs));
+    return std::move(lhs);
+}
+
+}  // namespace vold
+}  // namespace android
+