Can't use Rules to password protect existing nodes?

Thanks for your response.
With https://www.drupal.org/node/2371613#comment-9387241, I can get it to work. But I'm trying to get to this:

I'm using Drupal Commerce for a shop (I hope you know how Commerce works, or else this probably won't make much sense to you). I'm using rules to automatically create a Product Display when I create a product. I added a field "password" to the product-type. When a password is entered when I create a product, that password has to be used to password-protect the Product Display.
I don't know how to fit the password part to my rule. This is how my rule looks now:

EVENT:
After saving a new commerce product
ACTIONS:
Create a new entity (entity type=node, content type=product_display)
Set a data value (data=productdisplay-created:field_product_reference, value=commerce-product)
Safe entity (entity=product_display-created)

I hope you can help?

Thanks,

Mike.

When I create a new rule that react on the event: Before saving content, with the action to set the password (test) on a node of type product_display, I get this error (when saving a new product):

Notice: Undefined property: stdClass::$nid in auto_entitylabel_set_title() (line 230 of /drupal/sites/all/modules/auto_entitylabel/auto_entitylabel.module).
Notice: Undefined property: stdClass::$protected_node_show_title in _protected_node_save() (line 848 of /drupal/sites/all/modules/protected_node/protected_node.module).
PDOException: SQLSTATE[23000]: Integrity constraint violation: 1048 Column 'protected_node_show_title' cannot be null: INSERT INTO {protected_nodes} (protected_node_is_protected, protected_node_passwd, protected_node_show_title, nid, protected_node_emails, protected_node_hint) VALUES (:db_insert_placeholder_0, :db_insert_placeholder_1, :db_insert_placeholder_2, :db_insert_placeholder_3, :db_insert_placeholder_4, :db_insert_placeholder_5); Array ( [:db_insert_placeholder_0] => 1 [:db_insert_placeholder_1] => a94a8fe5ccb19ba61c4c0873d391e987982fbbd3 [:db_insert_placeholder_2] => [:db_insert_placeholder_3] => 86 [:db_insert_placeholder_4] => [:db_insert_placeholder_5] => ) in _protected_node_save() (line 853 of /drupal/sites/all/modules/protected_node/protected_node.module).

First I assumed it was because of the Auto Entity Label module (hence my other issue), but now it looks like the rule is in fact trying to set the password (test) but can't set it because it has no value for the 'protected_node_show_title' field in the database. Well, that's what I make of this error, but maybe I'm wrong.

Not sure if the title is still accurate, but I think the issue remains.