feature request "lockable directories"

Hi,
I think an option to lock (and unlock; like locking a door) would be a useful feature with encrypted directories.

By this the user could "lock" a sensitive directory and "unlock" it only when needed.

This could be integrated in an ext4 user tool, or in a new tool, for example
lockdir -l mydir # locking
lockdir -u mydir # unlocking

A locked directory cannot be accessed.
Both locking and unlocking shall ask for a password for just that directory. The password could be saved in an internal file within the directory, and auto-deleted after successful unlocking.

Thx
Uenal