SYSTEM AND METHOD FOR SECURE AND TRANSPARENT ELECTRONIC COMMUNICATION
CROSS-REFERENCE TO RELATED
 This patent application claims priority to U.S. Provisional Patent Application No. 60/483,300, filed Jan. 7, 2003 and entitled "SYSTEM AND METHOD FOR SECURE AND TRANSPARENT ELECTRONIC COMMUNICATION," the entirety of which is incorporated herein by reference.
FIELD OF THE INVENTION
 This invention relates generally to securing electronic messages in a computer network. More particularly, this invention relates to techniques for providing secure transparent electronic communications between users in a computer network.
BACKGROUND OF THE INVENTION
 Encryption is the process of using a cryptographic key to scramble the contents of an electronic message (i.e., the plaintext) rendering it unreadable by anyone but the holder of a corresponding key (i.e., the intended recipient), the result being an unintelligible message (i.e., the ciphertext). Decryption reverses the encryption process by converting ciphertext back to plaintext, thereby restoring the original message. Encryption and decryption can be used to provide message security. Message security, particularly electronic mail (e-mail) encryption and decryption, has seen a relatively low adoption rate amongst Internet users. Many users know that messages transmitted via open networks such as the Internet are plainly readable, yet they commonly do not use encryption to solve this problem. Furthermore, from organized studies to anecdotal evidence, many people seem to have difficulty with effectively using encryption software.
 As shown in FIG. 1, a traditional secure e-mail system includes e-mail server 106 in connection with user computer 102 and an open communications network such as Internet 1000. In order to send a message securely over Internet 1000, a user usually installs encryption software 104 on user computer 102. The user is then typically required to configure various settings in encryption software 104, including such things as key lengths, algorithms, passwords, and other security related parameters.
 The overarching architectural goal of secure electronic communication is to make encryption easy to use and ubiquitous. Unfortunately, security experts often view security as an "all-or-nothing" prospect. This has led to, for example, complex software, difficult to use interfaces, and poor performance. What is needed, then, is a secure, transparent electronic communication system that alleviates the need for end users to interact with encryption software.
BRIEF DESCRIPTION OF THE DRAWINGS
 FIG. 1 depicts an encryption software package running in a network environment according to the prior art.
 FIG. 2 illustrates a network with a server operating in proxy mode according to an embodiment of the present invention.
 FIG. 3 illustrates a network with a server operating in gateway mode according to an alternative embodiment of the present invention.
 FIG. 4 is a network diagram showing the logical connection of a server that provides secure transparent electronic communication according to an embodiment of the present invention.
 FIG. 5 is a flowchart depicting the process of sending a secure e-mail, according to an embodiment of the present invention.
 FIG. 6 is a flowchart depicting the process of receiving a secure e-mail, according to an embodiment of the present invention.
 FIG. 7 is an alternative embodiment of the present invention.
SUMMARY OF THE INVENTION
 This invention provides secure transparent electronic communication. It allows users to send and receive encrypted and/or signed messages with little or no user involvement. In an embodiment, secure transparent electronic communication provides end-user transparency. A user does not need to know the details of security or, for example, that a session is encrypted. Instead, the secure transparent electronic communication is provided by, for example, a separate server. Consequently, secure transparent electronic communication provides a user, in one embodiment, with e-mail security via automated hierarchical techniques for transparently sending and receiving secure messages. A second feature of secure transparent electronic communication is that it lowers the burden on administrators. It focuses the software setup on a relatively few servers rather than on many clients. Also, from an administrator perspective, secure transparent electronic communication allows for a public key infrastructure (PKI) to be dynamically constructed and operated. A third feature is that it offers a scale of tradeoffs of security with ease of use. In its most refined form, secure transparent electronic communication is encryption done entirely on servers. Secure transparent electronic communication interoperates fully with clientbased encryption, and provides even stronger security for users who demand such higher security. It further provides for sophisticated digital certificate searching for users that may not have cryptographic keys and certificates.
 An embodiment of the present invention includes a server in a local network that acts as a proxy between a user and an open communications network, with the server intercepting messages to or from the user in the local network and transforming those messages using indicia contained within or related to the messages, thereby providing transparent transmission and receipt of secure messages for the user. In an exemplary embodiment, a system according to the present invention could be used for sending and receiving secure e-mail. In another embodiment, such a system could be used for securing instant messaging (IM). In yet another embodiment, such a system manages cryptographic keys and certificates for the users, and creates such keys and certificates for the users when necessary.
 According to another aspect of the present invention, unsecured messages from a user are intercepted at a server, automatically transformed into secured messages,