Secure electronic message transport protocol

• US 20050198170A1
• Filed: 12/10/2004
• Published: 09/08/2005
• Est. Priority Date: 12/12/2003
• Status: Active Grant

• Current Assignee: WiSys Technology Foundation, Inc.
• Original Assignee: WiSys Technology Foundation, Inc.
• Inventors: LeMay, Michael, Tan, Jack
• Granted Patent: US 7,774,411 B2
• Time in Patent Office: Days
• US Class Current: 709/206
• CPC Class Codes: H04L 51/00 User-to-user messaging in packet-switching networks, transmitted according to store-and-forward or real-time protocols, e.g. e-mail
• CPC Class Codes: H04L 63/045 wherein the sending and receiving network entities apply hybrid encryption, i.e. combination of symmetric and asymmetric encryption cryptographic mechanisms or cryptographic arrangements using a plurality of keys or algorithms H04L9/14
• CPC Class Codes: H04L 63/126 the source of the received data

Abstract

An electronic message transport protocol applies two distinct sub-protocols, a message transport protocol and an encryption key management protocol, which operate in tandem to provide enhanced security. The protocol may employ an existing SMTP infrastructure to transport secure email messages, and a key server implementing the key management protocol to transport key packets associated with the secure email message. However, the protocol need not be limited to email, and may be applicable to other electronic message applications. The message transport protocol permits communicating parties to obscure their identities to enhance security. The key management protocol supports message security, and allows senders to control access to messages even after they have been transmitted. The message transport protocol permits the sender to encrypt the entire message and utilizes the key management protocol for exchange of necessary keys. The message transport protocol relies on a group addressing scheme to obscure individual sender and recipient identities.

Claims

1. A method comprising:

encrypting flow control information associated with an electronic message, the flow control information including identities of a sender and an intended recipient; and

transmitting the electronic message with the encrypted flow control information from the sender to a recipient group mailbox accessible by the intended recipient.

2. The method of claim 1, further comprising transmitting the electronic message with a recipient group mailbox identifier that does not reveal the intended recipient identity, and a sender group mailbox identifier that does not reveal the sender identity.

3. The method of claim 1, further comprising encrypting content of the electronic message with a message key, wherein transporting the electronic message includes transporting the electronic message with the encrypted content.

4. The method of claim 3, further comprising:

transmitting the message key from the sender to a message key server; and

transmitting an identity of the message key server from the sender to the recipient group mailbox with the electronic message.

5. The method of claim 4, generating a time stamp in response to receipt of the message key at the key server, further comprising providing corroboration of the time stamp from one or more clients communicating with the key server.

6. The method of claim 4, further comprising providing the recipient with access to the message key via the key server, wherein the message key is necessary for decryption of the encrypted flow control information.

9. The method of claim 1, further comprising:

generating a header;

encrypting the header using a public key associated with the recipient;

adding the header to the electronic message transmitted from the sender to the recipient group mailbox; and

permitting the recipient to accept the electronic message based on successful decryption of the header by the recipient using a private key that corresponds to the public key.

10. The method of claim 9, further comprising transmitting an identity of a message key server from the sender to the recipient group mailbox with the electronic message, and providing the recipient with access to the message key via the key server for decryption of the encrypted flow control information.

7. The method of claim 7, further comprising permitting the sender to invalidate the message key after transmitting the message key to the message key server to prevent the recipient from decrypting the encrypted flow control information.

8. The method of claim 7, further comprising permitting the sender to specify a period during which the message key is valid.

11. A system comprising:

a sender client that generates an electronic message and encrypts flow control information associated with the electronic message;

a recipient client that receives the electronic message, wherein the flow control information includes identities of the sender client and the recipient client;

one or more message transport servers that receive the electronic message with the encrypted flow control information from the sender client;

a recipient group mailbox, accessible by the receiver client, that receives the electronic message with the encrypted flow control information from the message transport servers.

12. The system of claim 11, wherein the sender client encrypts content of the electronic message, the electronic message being transmitted from the sender client to the message transport servers with the encrypted content.

13. The system of claim 11, wherein the electronic message includes a recipient group mailbox identifier that does not reveal the recipient client identity, and a sender group identifier that does not reveal the sender client identity.

14. The system of claim 11, wherein the sender client encrypts content of the electronic message and the flow control information using a message key.

15. The system of claim 14, further comprising a message key server, wherein the sender client transmits the message key to the message key server, and the electronic message includes an identity of the message key server.

16. The system of claim 15, wherein the message key server generates a time stamp in response to receipt of the message key, and the key server obtains corroboration of the time stamp from one or more clients communicating with the key server.

17. The system of claim 14, wherein the message key is necessary for decryption of the encrypted flow control information, and the key server provides the recipient client with access to the message key.

18. The system of claim 17, wherein the key server permits the sender client to invalidate the message key after the message key is received by the message key server to prevent the recipient client from decrypting the encrypted flow control information.

19. The system of claim 17, wherein the key server permits the sender client to specify a period during which the message key is valid.

20. The system of claim 11, wherein the sender client generates a header, encrypts the header using a public key associated with the recipient client, and adds the header to the electronic message transmitted from the sender client to the recipient group mailbox, the recipient client accesses the electronic message upon successful decryption of the header using a private key that corresponds to the public key, and wherein the electronic message identifies a key server, and the recipient client accesses the message key via the identified key server for decryption of the encrypted flow control information.

21. A computer-readable medium comprising instructions to cause a processor to:

encrypt flow control information associated with an electronic message, the flow control information including identities of a sender and an intended recipient; and

transmit the electronic message with the encrypted flow control information from the sender to a recipient group mailbox accessible by the intended recipient.

22. The computer-readable medium of claim 21, further comprising instructions to cause a processor to encrypt content of the electronic message, and transmit the electronic message with the encrypted content.

23. The computer-readable medium of claim 22, further comprising transmitting the electronic message with a recipient group mailbox identifier that does not reveal the intended recipient identity, and a sender group identifier that does not reveal the sender identity.

24. The computer-readable medium of claim 21, further comprising instructions to cause a processor to encrypt content of the electronic message and the flow control information using a message key, wherein the message key is necessary for decryption of the encrypted flow control information, and transport the electronic message with the encrypted content and the encrypted flow control information.

25. The computer-readable medium of claim 24, further comprising instructions to cause a processor to:

transmit the message key from the sender to a message key server; and

transmit an identity of the message key server from the sender to the recipient group mailbox with the electronic message.

26. A method comprising:

generating a symmetric message key;

encrypting an electronic message using the symmetric message key;

encrypting the symmetric message key using a public asymmetric key associated with a recipient of the electronic message;

transmitting the encrypted message key to a key server;

formulating a message header;

encrypting the header using the public asymmetric key associated with the recipient; and

attaching the encrypted header to the message.

27. The method of claim 26, further comprising transmitting the encrypted electronic message and encrypted header from a sender to a recipient group mailbox associated with the recipient.

28. The method of claim 26, wherein encrypting the electronic message includes encrypting flow control information associated with the electronic message, wherein the flow control information includes identities of a sender and an intended recipient.

29. The method of claim 26, further comprising:

compressing the electronic message;

generating a message digest based on the compressed electronic message;

signing the message digest using a private asymmetric key associated with a sender;

transmitting the message digest to the key server;

generating a digest of the message header; and

prepending the message header digest to the message header.

30. The method of claim 29, wherein the message header includes a sender group identification, a key server identification, a version of the message digest signed with a private asymmetric key associated with a sender group, and the message digest signed with the private asymmetric key associated with a sender.

31. The method of claim 30, further comprising:

decrypting the header using a private asymmetric key associated with the intended recipient;

accessing the key server identified by the key server identification in the header to retrieve the symmetric message key; and

decrypting the electronic message.

32. A method comprising:

receiving an electronic message encrypted with a symmetric message key, wherein the electronic message includes a message header encrypted with a public asymmetric key associated with a recipient;

decrypting the header using a private asymmetric key associated with the recipient;

identifying a key server based on an identification in the header;

accessing the key server to retrieve the symmetric message key; and

decrypting the electronic message using the symmetric message key.

33. The method of claim 32, further comprising encrypting the electronic message using the symmetric message key;

encrypting the symmetric message key using the public asymmetric key associated with a recipient of the electronic message;

transmitting the encrypted message key to the key server;

formulating the message header;

encrypting the header using the public asymmetric key associated with the recipient;

attaching the encrypted header to the message; and

transmitting the encrypted electronic message and encrypted header from a sender to a recipient group mailbox associated with the recipient.

34. A method comprising:

encrypting flow control information associated with an electronic message, the flow control information including identities of a sender and an intended recipient;

encrypting a symmetric message key using a public asymmetric key associated with a recipient of the electronic message;

transmitting the encrypted symmetric message key to a key server;

formulating a message header including the flow control information and an identification of the key server; and

transmitting the electronic message with the encrypted flow control information and the message header from the sender to a recipient group mailbox accessible by the intended recipient.

35. A method comprising:

encrypting flow control information associated with an electronic message using a symmetric message key associated with the sender, the flow control information including identities of a sender and an intended recipient;

encrypting the symmetric message key using a public asymmetric key associated with a recipient of the electronic message;

transmitting the encrypted symmetric message key to a key server;

generating a time stamp indicating a time at which the key server receives the encrypted message key;

transmitting the electronic message with the encrypted flow control information from the sender to a recipient group mailbox accessible by the intended recipient.

36. The method of claim 35, further comprising certifying the time stamp based on corroboration of the time by one or more clients in communication with the key server.

37. The method of claim 35, further comprising invalidating the encrypted symmetric message key at the key server based on a command received from the sender.

38. The method of claim 35, further comprising specifying an expiration time of the encrypted symmetric message key at the key server based on a command received from the sender.

39. The method of claim 35, wherein generating a time stamp includes:

signing the time stamp using a private key associated with the sender;

signing the time stamp received by the key server from the sender using a private key associated with the key server;

generating one or more copies of the time stamp; and

transmitting the copies to clients in communication with the key server, wherein each client certifies the copy by signing the copy using a private key associated with the client.