diff --git a/fulcrm_crypto.module b/fulcrm_crypto.module
index c72fa8e..c330724 100644
--- a/fulcrm_crypto.module
+++ b/fulcrm_crypto.module
@@ -34,6 +34,11 @@ function fulcrm_crypto_object_id_hmac( $object_type, $object_id ) {
     return drupal_hmac_base64( 'fulcrm:' . strval( $object_id ) . ':' . $object_type, session_id() . drupal_get_hash_salt() );
 }
 
+function fulcrm_crypto_check_object_id_hmac( $object_type, $object_id, $hmac ) {
+    $real_hmac = fulcrm_crypto_object_id_hmac( $object_type, $object_id );
+    return hash_equals( $real_hmac, $hmac );
+}
+
 function fulcrm_crypto_object_id_form_value( $object_type, $object_id ) {
     return $object_id . ':' . fulcrm_crypto_object_id_hmac( $object_type, $object_id );
 }