cryptographically secure mailing list software

[Matthew James Gering <mgering@ecosystems.net>]

I've been curious as to whether anyone has developed and/or whether it
is technically feasible to develop a cryptographically secure
listserver.

e.g. 

User would submit their PGP public key to the listserver upon
subscription, submitted messages would be encrypted with the
listserver's public key, the listserver would decrypt the message and
re-encrypt it with the key of all members and distribute it. This way
the users don't need to manage all the keys or even know the list
membership. Most listservers already have the ability to moderate
subscription messages, the list would not be snoopable.

What sort of overhead would exist on a list of a few hundred members?

If there is not something existing that will do this, what is the best
mailing list codebase to start from? Majodomo I imagine might not be up
to the task being written in Perl, LSoft ListSERV I love but it is
commercial (no sourcecode).

	Matt