diff --git a/presence/proto/presence_frame.proto b/presence/proto/presence_frame.proto
index ee6c2db9..987d2ae2 100644
--- a/presence/proto/presence_frame.proto
+++ b/presence/proto/presence_frame.proto
@@ -40,6 +40,9 @@ message V1Frame {
 
     // Sent by discoverer to notify broadcaster the UWB ranging parameters.
     UwbConnectionInfo uwb_connection_info = 5;
+
+    // Used for identity authentication.
+    PresenceAuthenticationFrame authentication_frame = 6;
   }
 }
 
@@ -156,3 +159,16 @@ message ControlFrame {
 
   optional ControlType type = 1;
 }
+
+message PresenceAuthenticationFrame {
+  // The version of this frame and protocol.
+  optional int32 version = 1;
+
+  // A signature signed by the private key in the LocalCredential.
+  optional bytes private_key_signature = 2;
+
+  // A hash of the credential's id.
+  optional bytes credential_id_hash = 3;
+
+  // TBD. Keychain PSK hash (go/nearby-presence-identity-verification).
+}