SECURE ELECTRONIC MESSAGING SYSTEM REQUIRING KEY RETRIEVAL FOR DERIVING DECRYPTION KEYS

A secure electronic messaging system permits communication between registere d users, with the assistance of a key server (240). The system requires a recipient (220) to submit key retrieval information to a key server (240), a nd obtain decryption key information. The decryption key information is necessa ry for the recipient (220) to form the decryption key which is used to read a message encrypted by the sender (210). The decryption key information may be an encrypted version of a decryption key, or portions thereof, or may be portions of an unencrypted version of a decryption key, among others. Typically, the key retrieval information may either be sent to the recipient (220) by the sender (210), or may be generated by the recipient (220), based on information sent by the sender (210).