diff --git a/libs/binder/include/binder/CertificateFormat.h b/libs/binder/include/binder/CertificateFormat.h
new file mode 100644
index 0000000..4f7e71e
--- /dev/null
+++ b/libs/binder/include/binder/CertificateFormat.h
@@ -0,0 +1,28 @@
+/*
+ * Copyright (C) 2021 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.
+ */
+
+// Formats for serializing TLS certificate.
+
+#pragma once
+
+namespace android {
+
+enum class CertificateFormat {
+    PEM,
+    // TODO(b/195166979): support other formats, e.g. DER
+};
+
+} // namespace android
diff --git a/libs/binder/include/binder/RpcTransport.h b/libs/binder/include/binder/RpcTransport.h
index 8d08b34..9e6faf6 100644
--- a/libs/binder/include/binder/RpcTransport.h
+++ b/libs/binder/include/binder/RpcTransport.h
@@ -25,15 +25,12 @@
 #include <android-base/unique_fd.h>
 #include <utils/Errors.h>
 
+#include <binder/CertificateFormat.h>
+
 namespace android {
 
 class FdTrigger;
 
-enum class CertificateFormat {
-    PEM,
-    // TODO(b/195166979): support other formats, e.g. DER
-};
-
 // Represents a socket connection.
 // No thread-safety is guaranteed for these APIs.
 class RpcTransport {