How to make private (hidden) node path aliases?
There is different solutions


https://www.drupal.org/sandbox/ajlee/2109425 (disable access to nodes through the "normal" URL such as node/123)
https://www.drupal.org/project/access_unpublished (key to give view access to unpublished node)
https://www.drupal.org/project/node_authlink authorization key for every node and gives additional grants (view/edit/delete) to every user (anonymous too) who accesses page with correct key in URL