(One Time) Access Code

Hi Community,

I am new to Drupal and I am still in a experimenting stage with its overwhelming features.

One use-case I want to implement is a restricted access to a webform or a page with a (one-time) password/access code for anonymous users. Access should be granted to a webform or a restricted page area during this session or during the webform is not closed.
One time password/access codes should be generated as a list.

I would be proud if you can give me a hint, how I can implement such a feature.

Thanks a lot,
Chris