diff --git a/includes/class-signature.php b/includes/class-signature.php
index 66b16ba..a91ea0e 100644
--- a/includes/class-signature.php
+++ b/includes/class-signature.php
@@ -245,7 +245,7 @@ class Signature {
 	 * @return string The public key.
 	 */
 	public static function get_remote_key( $key_id ) { // phpcs:ignore
-		$actor = \Activitypub\get_remote_metadata_by_actor( strtok( strip_fragment_from_url( $key_id ), '?' ) ); // phpcs:ignore
+		$actor = get_remote_metadata_by_actor( strtok( strip_fragment_from_url( $key_id ), '?' ) ); // phpcs:ignore
 		if ( \is_wp_error( $actor ) ) {
 			return $actor;
 		}
diff --git a/includes/class-user-factory.php b/includes/class-user-factory.php
index 8ba4521..db3be67 100644
--- a/includes/class-user-factory.php
+++ b/includes/class-user-factory.php
@@ -5,6 +5,7 @@ use WP_Error;
 use WP_User_Query;
 use Activitypub\Model\User;
 use Activitypub\Model\Blog_User;
+use Activitypub\Model\Application_User;
 
 class User_Factory {
 	/**
@@ -63,7 +64,7 @@ class User_Factory {
 		}
 
 		// check for application user.
-		if ( get_option( 'activitypub_application_user_identifier', null ) === $username ) {
+		if ( 'application' === $username ) {
 			return self::get_by_id( self::APPLICATION_USER_ID );
 		}
 
diff --git a/includes/model/class-application-user.php b/includes/model/class-application-user.php
index 1e562b1..fe5fcc8 100644
--- a/includes/model/class-application-user.php
+++ b/includes/model/class-application-user.php
@@ -2,8 +2,11 @@
 namespace Activitypub\Model;
 
 use WP_Query;
+use Activitypub\Signature;
 use Activitypub\User_Factory;
 
+use function Activitypub\get_rest_url_by_path;
+
 class Application_User extends Blog_User {
 	/**
 	 * The User-ID
@@ -24,7 +27,7 @@ class Application_User extends Blog_User {
 	 *
 	 * @param int $user_id The User-ID.
 	 */
-	public function __construct( $user_id ) {
+	public function __construct( $user_id = null ) {
 		// do nothing
 	}
 
@@ -34,11 +37,15 @@ class Application_User extends Blog_User {
 	 * @return string The User-Url.
 	 */
 	public function get_url() {
-		return '';
+		return get_rest_url_by_path( 'application' );
 	}
 
 	public function get_name() {
-		return \esc_html( \get_option( 'activitypub_application_identifier', 'application' ) );
+		return 'application';
+	}
+
+	public function get_username() {
+		return $this::get_name();
 	}
 
 	public function get_public_key() {
diff --git a/includes/rest/class-server.php b/includes/rest/class-server.php
index 351284d..3b78af2 100644
--- a/includes/rest/class-server.php
+++ b/includes/rest/class-server.php
@@ -4,11 +4,7 @@ namespace Activitypub\Rest;
 use stdClass;
 use WP_REST_Response;
 use Activitypub\Signature;
-use Activitypub\Model\User;
-
-use function Activitypub\get_context;
-use function Activitypub\get_rest_url_by_path;
-
+use Activitypub\Model\Application_User;
 
 /**
  * ActivityPub Server REST-Class
@@ -18,7 +14,6 @@ use function Activitypub\get_rest_url_by_path;
  * @see https://www.w3.org/TR/activitypub/#security-verification
  */
 class Server {
-
 	/**
 	 * Initialize the class, registering WordPress hooks
 	 */
@@ -50,21 +45,8 @@ class Server {
 	 * @return WP_REST_Response The JSON profile of the Application Actor.
 	 */
 	public static function application_actor() {
-		$json = new stdClass();
-
-		$json->{'@context'} = get_context();
-		$json->id = get_rest_url_by_path( 'application' );
-		$json->type = 'Application';
-		$json->preferredUsername = str_replace( array( '.' ), '-', wp_parse_url( get_site_url(), PHP_URL_HOST ) ); // phpcs:ignore WordPress.NamingConventions
-		$json->name = get_bloginfo( 'name' );
-		$json->summary = __( 'WordPress-ActivityPub application actor', 'activitypub' );
-		$json->manuallyApprovesFollowers = true; // phpcs:ignore WordPress.NamingConventions
-		$json->icon = array( get_site_icon_url() ); // phpcs:ignore WordPress.NamingConventions short array syntax
-		$json->publicKey = array( // phpcs:ignore WordPress.NamingConventions
-			'id' => get_rest_url_by_path( 'application#main-key' ),
-			'owner' => get_rest_url_by_path( 'application' ),
-			'publicKeyPem' => Signature::get_public_key( User::APPLICATION_USER_ID ), // phpcs:ignore WordPress.NamingConventions
-		);
+		$user = new Application_User();
+		$json = $user->to_array();
 
 		$response = new WP_REST_Response( $json, 200 );
 
diff --git a/tests/test-class-activitypub-rest-post-signature-verification.php b/tests/test-class-activitypub-rest-post-signature-verification.php
index f0acd34..2b7fc29 100644
--- a/tests/test-class-activitypub-rest-post-signature-verification.php
+++ b/tests/test-class-activitypub-rest-post-signature-verification.php
@@ -42,7 +42,9 @@ class Test_Activitypub_Signature_Verification extends WP_UnitTestCase {
 		$signed_headers = $signature_block['headers'];
 		$signed_data = Activitypub\Signature::get_signed_data( $signed_headers, $signature_block, $headers );
 
-		$public_key = Activitypub\Signature::get_public_key( 1 );
+		$user = Activitypub\User_Factory::get_by_id( 1 );
+
+		$public_key = $user->get_public_key();
 
 		// signature_verification
 		$verified = \openssl_verify( $signed_data, $signature_block['signature'], $public_key, 'rsa-sha256' ) > 0;
@@ -53,6 +55,8 @@ class Test_Activitypub_Signature_Verification extends WP_UnitTestCase {
 		add_filter(
 			'pre_get_remote_metadata_by_actor',
 			function( $json, $actor ) {
+				$user = Activitypub\User_Factory::get_by_id( 1 );
+				$public_key = $user->get_public_key();
 				// return ActivityPub Profile with signature
 				return array(
 					'id' => $actor,
@@ -60,7 +64,7 @@ class Test_Activitypub_Signature_Verification extends WP_UnitTestCase {
 					'publicKey' => array(
 						'id' => $actor . '#main-key',
 						'owner' => $actor,
-						'publicKeyPem' => \Activitypub\Signature::get_public_key( 1 ),
+						'publicKeyPem' => $public_key,
 					),
 				);
 			},