A technique, and system(s) implementing the technique, allow an encrypted message to be sent directly to a recipient, and when the recipient opens the message, the recipient's system sends a request to an arbiter server to retrieve decryption information to decrypt the message. When the arbiter server...http://www.google.nl/patents/US6904521?utm_source=gb-gplus-sharePatent US6904521 - Non-repudiation of e-mail messages
