Support for client certificates would be cool. AFAIK there
is no server yet that supports this, but it would become a very
interesting feature once there are such servers. With a client
certificate, the server verifies the certificate of a client before it
allows a connection. If the certificate is invalid or revoked, the
connection is aborted before it even is established.
This feature could be very useful in a scenario to prevent abuse:
1) The server admin sells self-signed client certificates for his
server for a very small amount (micro payments)
2) The server only allows connections from clients that have a valid certificate
3) If people want multiple account they have to buy more certificates
4) If people start to abuse the server (e.g. spam), the server admin
simply revokes their certificate(s) so that it becomes invalid. No
connection can be made with that certificate any more.
5) In order to connect again to the server, the abuser would have to
buy a new certificate.
--> Advantages:
1) Good users only have to pay a small one-time fee to get a reliable
spam-free service
2) Admins get a small source of funding to pay the hosting bill
3) Bad users who need to have multiple accounts, need to buy multiple
certificates *and* their certificates get revoked so that they have to
pay new ones-->Abuse gets very expensive!
Related: http://