Ubuntu Security :: Encryption, Luks, "auto"-mount, But Ask For Password?

I know how to mount it manually. I've seen a howto on how to mount it automatically by loging in with the user, you type your username and password and it mounts your encrypted partition. But that's not what I want. My idea is to call cryptsetup and mount on boot, AND ask me for passphrase like when its loading the system, then if I don't type the right password it shouldn't mount /home, even though i type the correct USER password later when the system is loaded(and then I'd have an empty /home since my home partition wasn't mounted due to wrong passphrase).

This is what I tried: I added the commands to rc.local and I don't even feel like it was executed, no passphrase was asked. As a test if commands there were being executed, I tried simple commands lile mkdir /test and it worked. So commands there are executed, yet, no passphrase was asked to me, I looked on dmesg for crypt and found nothing, I pressed alt+ctrl+F1 desiring to find a passprhase-ask and again, nothing.