[Zope-dev] storing passwords

Hello, I want to use the same usernames and passwords in Zope and some other servers. The usernames and password digests are stored in a PostgreSQL database, and a given username and password -pair can be checked with a simple SQL-query. I need to modify Zope to look up and to save passwords in PostgreSQL. Has someone done this before? Can someone tell me which source file contains the method that reads or saves passwords? Can this be done by modifying only one source file? Markus