One embodiment of the present invention provides a system that performs, content screening on a message that is protected by end-to-end encryption. The system operates by receiving an encrypted message at a firewall from a source outside of the firewall, the encrypted message having been formed by encrypting...http://www.google.ca/patents/US6546486?utm_source=gb-gplus-sharePatent US6546486 - Content screening with end-to-end encryption within a firewall
