how to revoke the passphrase/key for nautilus (ubuntu)

hi,
I have an external luks usb-HD.
how to to revoke the passphrase/key for nautilus (under ubuntu) which I seemingly, accidentally set to 'remember forever' instead of 'until I logout'?
(if I plug in the luks disk and click on mount in nautilus, it is mounted without requiring the key to unlock the device. I want to undo this.)

I already searched quite a while withour success:
search results point to gvfs, gnome-keyring and "Passwords and Keys" but there is no respective entry.

Thanks!

The key is stored in gnome-keyring and cryptsetup is not involved at all.

Use seahorse[1] to remove the key from gnome's keyring.

[1]
https://wiki.gnome.org/action/show/Apps/Seahorse?action=show&redirect=Seahorse