Crypt in queries and functions?

Salve.

I'm writing Yet Another Web Forum and I'm using pgsql as the backend.
I'd like to do user creation and authentication through functions,
rather like:

SELECT Create_User ('Owen', 'password', 'ojacobson@mx-deus.net');

Passwords should, for obvious reasons, be stored encrypted.  I'm
inclined to do this in a unixish way, using crypt().  However, there
doesn't seem to be a crypt function in PostgreSQL's function list.  How
would I go about wrapping or importing the C one?  Is there a better way?

Ideally I'd like to be able to do something like

(table Users has column Password as varchar)

SELECT * FROM Users WHERE crypt('untested password', Password) = Password;

to verify passwords.

Any thoughts?

Owen