>> page Accessibility

I create a lot of page in a wp site where theres a lot of user
each of them all have a dedicated post page with a specificinfos
but theres pages aren't hidden for the moment
How can I do to have hidden page from everybody and allow access to the page via a code.
Aim is to flash a rires code and direct access to page, but if someone type it in a browser, its inaccessible. Just via a QR code
Thank you