--- a/mod_http_oauth2/mod_http_oauth2.lua	Sun Jun 25 23:53:15 2023 +0200
+++ b/mod_http_oauth2/mod_http_oauth2.lua	Mon Jun 26 00:19:05 2023 +0200
@@ -1018,10 +1018,6 @@
 		return nil, oauth_error("invalid_client_metadata", "No allowed 'response_types' specified");
 	end
 
-	-- Ensure each signed client_id JWT is unique, short ID and issued at
-	-- timestamp should be sufficient to rule out brute force attacks
-	client_metadata.nonce = id.short();
-
 	-- Do we want to keep everything?
 	local client_id = sign_client(client_metadata);
 
@@ -1029,7 +1025,14 @@
 	client_metadata.client_id_issued_at = os.time();
 
 	if client_metadata.token_endpoint_auth_method ~= "none" then
-		local client_secret = make_client_secret(client_id);
+		-- Ensure that each client_id JWT with a client_secret is unique.
+		-- A short ID along with the issued at timestamp should be sufficient to
+		-- rule out brute force attacks.
+		-- Not needed for public clients without a secret, but those are expected
+		-- to be uncommon since they can only do the insecure implicit flow.
+		client_metadata.nonce = id.short();
+
+		local client_secret = make_client_secret(client_id, client_metadata);
 		client_metadata.client_secret = client_secret;
 		client_metadata.client_secret_expires_at = 0;