diff --git a/includes/class-signature.php b/includes/class-signature.php
index 64467b7..2c5be60 100644
--- a/includes/class-signature.php
+++ b/includes/class-signature.php
@@ -242,6 +242,11 @@ class Signature {
 	 * @return string $publicKeyPem
 	 */
 	public static function get_remote_key( $key_id ) { // phpcs:ignore
+		$pre = apply_filters( 'pre_get_remote_key', false, $key_id );
+		if ( $pre ) {
+			return $pre;
+		}
+
 		$actor = \Activitypub\get_remote_metadata_by_actor( strtok( strip_fragment_from_url( $key_id ), '?' ) ); // phpcs:ignore
 		if ( \is_wp_error( $actor ) ) {
 			return $actor;
diff --git a/tests/test-class-activitypub-rest-post-signature-verification.php b/tests/test-class-activitypub-rest-post-signature-verification.php
index e9335fa..e87b1fd 100644
--- a/tests/test-class-activitypub-rest-post-signature-verification.php
+++ b/tests/test-class-activitypub-rest-post-signature-verification.php
@@ -1,6 +1,35 @@
 <?php
 
-class Test_Activitypub_Rest_Post_Signature_Verification extends WP_UnitTestCase {
+class Test_Activitypub_Signature_Verification extends WP_UnitTestCase {
+	public $server;
+	public function setUp() : void {
+		parent::setUp();
+
+		/**
+		 * Global $wp_rest_server variable
+		 *
+		 * @var WP_REST_Server $wp_rest_server Mock REST server.
+		 */
+		global $wp_rest_server;
+		add_filter( 'pre_get_remote_key', array( get_called_class(), 'pre_get_remote_key' ), 10, 2 );
+		$wp_rest_server = new \WP_REST_Server();
+		$this->server   = $wp_rest_server;
+
+		do_action( 'rest_api_init' );
+
+	}
+
+	/**
+	 * Tear down after test ends
+	 */
+	public function tearDown() : void {
+		remove_filter( 'pre_get_remote_key', array( get_called_class(), 'pre_get_remote_key' ) );
+		parent::tearDown();
+
+		global $wp_rest_server;
+		$wp_rest_server = null;
+
+	}
 
 	public function test_activity_signature() {
 
@@ -55,5 +84,61 @@ class Test_Activitypub_Rest_Post_Signature_Verification extends WP_UnitTestCase
 		remove_filter( 'pre_http_request', array( $pre_http_request, 'filter' ), 10 );
 	}
 
+	public function test_rest_activity_signature() {
+
+		$pre_http_request = new MockAction();
+		// $pre_get_remote_key = new MockAction();
+		add_filter( 'pre_http_request', array( $pre_http_request, 'filter' ), 10, 3 );
+		add_filter( 'pre_get_remote_key', array( get_called_class(), 'pre_get_remote_key' ), 10, 2 );
+
+		// Activity Object
+		$post = \wp_insert_post(
+			array(
+				'post_author' => 1,
+				'post_content' => 'hello world',
+			)
+		);
+		$remote_actor = \get_author_posts_url( 2 );
+		$remote_actor_inbox = \get_rest_url( null, 'activitypub/1.0/inbox' );
+		$activitypub_post = new \Activitypub\Model\Post( $post );
+		$activitypub_activity = new Activitypub\Model\Activity( 'Create' );
+		$activitypub_activity->from_post( $activitypub_post );
+		$activitypub_activity->add_cc( $remote_actor_inbox );
+		$activity = $activitypub_activity->to_json();
+
+		// generate_digest & generate_signature
+		$digest = Activitypub\Signature::generate_digest( $activity );
+		$date = gmdate( 'D, d M Y H:i:s T' );
+		$signature = Activitypub\Signature::generate_signature( 1, 'POST', $remote_actor, $date, $digest );
+
+		//  Signed headers
+		$url_parts = wp_parse_url( $remote_actor );
+		$route = add_query_arg( $url_parts['query'], $url_parts['path'] );
+		$host = $url_parts['host'];
+
+		$request  = new WP_REST_Request( 'POST', ACTIVITYPUB_REST_NAMESPACE . '/inbox' );
+		$request->set_header( 'content-type', 'application/activity+json' );
+		$request->set_header( 'digest', "SHA-256=$digest" );
+		$request->set_header( 'signature', $signature );
+		$request->set_header( 'date', $date );
+		$request->set_header( 'host', $host );
+		$request->set_body( $activity );
+
+		// Start verification
+		$verified = \Activitypub\Signature::verify_http_signature( $request );
+		// $this->assertTRUE( $verified );
+
+		remove_filter( 'pre_get_remote_key', array( get_called_class(), 'pre_get_remote_key' ) );
+		remove_filter( 'pre_http_request', array( $pre_http_request, 'filter' ), 10 );
+	}
+
+	public static function pre_get_remote_key( $pre, $key_id ) {
+		$query = wp_parse_url( $key_id, PHP_URL_QUERY );
+		parse_str( $query, $output );
+		if ( is_int( $output['author'] ) ) {
+			return ActivityPub\Signature::get_public_key( int( $output['author'] ) );
+		}
+		return $pre;
+	}
 
 }