Enhanced cryptographic system and method with key escrow feature

• US 5,799,086 A
• Filed: 02/19/1997
• Issued: 08/25/1998
• 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:
  US08/803,176
• Time in Patent Office: 552 Days
• Field of Search: 380/30, 380/23
• US Class Current: 705/76
• 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

A cryptographic system with key escrow feature that uses a method for verifiably splitting user'"'"'s private encryption keys into components and for sending those components to trusted agents chosen by the particular users is provided. The system uses public key certificate management, enforced by a chip device that also self-certifies. The methods for key escrow and receiving an escrow certificate are applied to register a trusted device with a trusted third party and to receive authorization from that party enabling the device to communicate with other trusted devices. The methods for key escrow also provide assurance that a trusted device will engage in electronic transactions in accordance with predetermined rules.

Claims

1. A method of authorizing a trusted device to conduct an electronic transaction between a first user and a second party, and providing assurance that said trusted device will engage in said electronic transaction in accordance with predetermined rules which cannot be changed by said user, said method comprising:

electronically transmitting from said trusted device to a third party a request for authorization to engage in said electronic transaction, said request including the identity of said trusted device;

determining, by said third party, that said trusted device should be authorized to engage in said transaction at least in part in accordance with a determination that said trusted device will operate only in accordance with said rules;

electronically transmitting from said third party to said trusted device authorization to engage in said electronic transaction, said authorization including certification that said third party provided said authorization;

electronically transmitting from said trusted device to said second party said certification as assurance that said trusted device is authorized to engage in said electronic transaction and will do so only in accordance with said rules;

electronically transmitting transaction data from said trusted device to said second party in accordance with said rules.

2. A method as in claim 1 wherein said authorization transmitting step includes the step of transmitting said rules from said third party to said trusted device.

3. A method as in claim 1 wherein said trusted device contains said rules prior to said authorization transmitting step.

4. A method as in claim 1 wherein said authorization transmitting step includes the step of appending a digital signature of said third party to said certification.

5. A method as in claim 1 wherein said request transmitting step includes the step of transmitting certification of said identity of said trusted device digitally signed by a manufacturer of said trusted device.

6. A method as in claim 1 wherein said determining step includes the step of determining whether said trusted device is tamper-resistant based upon said identity of said trusted device.

7. A method as in claim 1 wherein said trusted device has associated with it a public key and a private key of an asymmetric cryptosystem and said request transmitting step includes the step of transmitting said device public key to said third party.

8. A method as in claim 1 wherein said trusted device has associated with it a first key and a second key of an asymmetric cryptosystem and said step of transmitting transaction data to said second party includes a step of appending a digital signature of said trusted device created with said first key.

9. A method as in claim 5 wherein said identity certification includes a public key of a public-private key pair for said trusted device and said request transmitting step includes appending a digital signature of said trusted device created with said device private key to said request so that said third party can confirm that said request came from said trusted device.

10. A method as in claim 8 wherein said step of transmitting transaction data to said second party includes a step of transmitting said second key to said second party.

11. A method as in claim 8 wherein said first and second device keys are private and public keys respectively.

12. A method as in claim 10 wherein said first and second device keys are private and public keys respectively.