Shibboleth: Private Mailing List Manager

We describe Shibboleth, a program to manage private Internet mailing lists. Differing from other mailing list managers, Shibboleth manages lists or groups of lists that are closed, or have membership by invitation only. So instead of focusing on automating the processes of subscribing and unsubscribing readers, we include features like SMTP forgery detection, prevention of outsiders' ability to harvest usable email addresses from mailing list archives, and support for cryptographic strength user authentication and nonrepudiation.