Add crypto service

Change-Id: Ifd55a4caaf0b95e3d1b6504863fba112a7e18f15
Signed-off-by: Julian Hall <julian.hall@arm.com>
diff --git a/protocols/service/crypto/protobuf/open_key.proto b/protocols/service/crypto/protobuf/open_key.proto
new file mode 100644
index 0000000..90fb2ad
--- /dev/null
+++ b/protocols/service/crypto/protobuf/open_key.proto
@@ -0,0 +1,15 @@
+/*
+ * Copyright (c) 2020, Arm Limited and Contributors. All rights reserved.
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+syntax = "proto3";
+
+package ts_crypto;
+
+message OpenKeyIn {
+  uint32 id = 1;
+}
+
+message OpenKeyOut {
+  uint32 handle = 1;
+}