Protocol-level changes required to support PIN-less authentication.

remoting/proto/control.proto

Index: remoting/proto/control.proto
diff --git a/remoting/proto/control.proto b/remoting/proto/control.proto
index 88eda00f68fd8c9c0e5d93dd45436d8847417cbc..888c0b01b90108757fcbcf33d71554da7a39a749 100644
--- a/remoting/proto/control.proto
+++ b/remoting/proto/control.proto
@@ -53,3 +53,16 @@ message Capabilities {
   // are separated by spaces).
   optional string capabilities = 1;
 }
+
+message PairingRequest {
+  // Human-readable name of the client.
+  optional string client_name = 1;
+}
+
+message PairingResponse {
+  // Unique identifier for this client.
+  optional string client_id = 1;
+
+  // Shared secret for this client.
+  optional string shared_secret = 2;
+}