Securing electronic mail systems

It is pointed out that security at the network layer cannot provide application-specific services associated with electronic mail such as signed receipts and digital signatures. These deficiencies can be remedied by providing end user to end user security where mail messages are black (protected/encrypted) at all intermediate points. The authors describe the approach and implementation taken in building such a mail security device. Mail messages are protected along the entire path from originator to recipient. The messages are protected during storage and processing at all intermediate points. the security can be implemented independently of the network layer architecture or a network layer security device. The key distribution technique is suitable for client-server architectures such as electronic mail, where the number of users is large and connectivity is diverse