Enhanced cryptographic system and method with key escrow feature

• US 5,850,451 A
• Filed: 02/19/1997
• Issued: 12/15/1998
• Est. Priority Date: 01/13/1994
• Status: Expired due to Term

• Current Assignee: Certco
• Original Assignee: Certco
• Inventors: Sudia, Frank Wells
• Primary Examiner(s): Barron, Jr., Gilberto
• Application Number:
  US08/803,024
• Time in Patent Office: 664 Days
• Field of Search: 380/30, 380/48, 380/42, 380/49
• US Class Current: 380/286
• CPC Class Codes: G06F 7/725 over elliptic curves
• CPC Class Codes: G06Q 20/02 involving a neutral party, e.g. certification authority, notary or trusted third party [TTP]
• CPC Class Codes: G06Q 20/3821 Electronic credentials
• CPC Class Codes: G06Q 20/3829 involving key management
• CPC Class Codes: H04L 9/0825 using asymmetric-key encryption or public key infrastructure [PKI], e.g. key signature or public key certificates
• CPC Class Codes: H04L 9/0844 with user authentication or key authentication, e.g. ElGamal, MTI, MQV-Menezes-Qu-Vanstone protocol or Diffie-Hellman protocols using implicitly-certified keys
• CPC Class Codes: H04L 9/085 Secret sharing or secret splitting, e.g. threshold schemes
• CPC Class Codes: H04L 9/088 Usage controlling of secret information, e.g. techniques for restricting cryptographic keys to pre-authorized uses, different access levels, validity of crypto-period, different key- or password length, or different strong and weak cryptographic algorithms network architectures or network communication protocols for using time-dependent keys in a packet data network H04L63/068
• CPC Class Codes: H04L 9/0894 Escrow, recovery or storing of secret information, e.g. secret key escrow or cryptographic key storage
• CPC Class Codes: H04L 9/3247 involving digital signatures
• CPC Class Codes: H04L 9/3263 involving certificates, e.g. public key certificate [PKC] or attribute certificate [AC]; Public key infrastructure [PKI] arrangements network architectures or network communication protocols for supporting authentication of entities using certificates in a packet data network H04L63/0823

Abstract

The invention provides a cryptographic system and method with a key escrow feature that uses a method for verifiably splitting users'"'"' private encryption keys into components and for sending those components to trusted agents chosen by the particular users, and provides a system that uses modern public key certificate management, enforced by a chip device that also self-certifies. In a preferred embodiment of this invention, the chip encrypts or decrypts only if certain conditions are met, namely, (1) if a valid "sender certificate" and a valid "recipient certificate" are input, where "valid" means that the particular user'"'"'s private decryption key is provably escrowed with a specified number of escrow agents and that the master escrow center is registered and certified by the chip manufacturer, and (2) if a valid Message Control Header is generated by the sender and validated by the recipient, thereby giving authorized investigators sufficient information with which to request and obtain the escrowed keys. A preferred embodiment provides for encryption of stream-oriented data.

Claims

1. A method for generating verifiably trusted, stream-oriented communications among a plurality of users, comprising the steps of:

escrowing at a trusted escrow center an asymmetric cryptographic key associated with each of a plurality of users;

verifying each of the keys at the escrow center;

certifying each of the keys upon verification; and

generating an encrypted stream-oriented communication from an initiating user to a receiving user using said initiating user'"'"'s cryptographic key, said communication comprising (a) an initial packet having access information to allow an outside party to decrypt the stream, and (b) a stream of subsequent packets, each subsequent packet containing information identifying the subsequent packet as associated with the stream, and wherein at least one of said subsequent packets does not include said access information.

2. The method of claim 1 wherein the communication further comprises a terminal packet having information indicating an end of the communication.

3. The method of claim 1 wherein each subsequent packet further includes unique information indicating a position of the packet within the sequence.

4. The method of claim 1 wherein each subsequent packet further includes timestamp information.

5. The method of claim 1, wherein the access information includes a hash of the initial packet.

6. The method of claim 5, wherein said hash of said initial packet is signed with the initiating user'"'"'s cryptographic key.

7. The method of claim 4, wherein said access information further includes message identifying information.

8. The method of claim 7, wherein at least one of the subsequent packets includes the message identifying information.

9. The method of claim 8, wherein said information identifying the subsequent packet as associated with the stream is a packet sequence number.

10. The method of claim 1, further comprising the steps of:

receiving, at the initiating user, information relating to a quality of a channel carrying the stream-oriented communication; and

selectively including message identifying information in subsequent packets at a rate determined by the quality of the channel.

11. The method of claim 1, wherein packets include information associating them with the initiating user.

12. A method for generating verifiably trusted, stream-oriented communications among a plurality of users, comprising the steps of:

escrowing at a trusted escrow center an asymmetric cryptographic key associated with each of a plurality of users;

verifying each of the keys at the escrow center;

certifying each of the keys upon verification; and

receiving, at a receiving user, a first encrypted stream-oriented communication from an initiating user, said communication having been encrypted using said initiating user'"'"'s cryptographic key, said first communication comprising (a) an initial packet having access information to allow an outside party to decrypt the stream, and (b) a stream of subsequent packets, each subsequent packet containing information identifying the subsequent packet as associated with the stream, and wherein at least one subsequent packet of the first stream does not include said access information.

13. The method of claim 12 further comprising the steps of:

generating a second encrypted stream-oriented communication from the receiving user to an initiating user using a cryptographic key of the receiving user, said second communication comprising (a) an initial packet having access information to allow an outside party to decrypt the second encrypted stream, and (b) a stream of subsequent packets, each subsequent packet containing information identifying the subsequent packet as associated with the second encrypted stream.

14. The method of claim 13, wherein the access information of the second encrypted stream includes a hash of the initial packet of the second encrypted stream signed with the receiving user'"'"'s cryptographic key.

15. The method of claim 14, wherein the access information of the second encrypted stream includes message identifying information received from the initiating user.

16. The method of claim 15, wherein at least one of the subsequent packets of the second encrypted stream includes message identifying information.

17. The method of claim 16, wherein the information identifying a subsequent packet of the second encrypted stream as associated with the second encrypted stream is a packet sequence number.

18. The method of claim 17, wherein packets of the second encrypted stream include information associating them with the initiating user.

19. The method of claim 13, further comprising the steps of:

receiving, at the receiving user, information relating to a quality of a channel carrying the stream-oriented communication; and

selectively including message identifying information in subsequent packets at a rate determined by the quality of the channel.

20. The method of claim 19, wherein the information relating to a quality of the channel is continuously received and the rate at which identifying information is selectively included in subsequent packets is dynamically adjusted based upon the received information.