Enhanced cryptographic system and method with key escrow feature

• US 5,857,022 A
• Filed: 02/19/1997
• Issued: 01/05/1999
• 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:
  US08/802,584
• Time in Patent Office: 685 Days
• Field of Search: 380/30, 380/23, 380/49
• US Class Current: 713/173
• 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.

Claims

1. A method for generating a verifiably trusted communication between a plurality of users comprising the steps of:

generating a secure communication within an electronic hardware device of a first user, said secure communication including access information to permit access to the secure communication by an outside party;

signing the secure communication with a chip specific private signature key of a signing chip of the electronic hardware device of the first user, said chip specific private signature key having been embedded within a tamper-resistant memory associated with the signing chip of the first user prior to the electronic hardware device being provided to the first user;

appending a certificate to the secure communication, said certificate including a public signature key, corresponding to the private signature key of the signing chip of the first user, signed with a private signature key of a trusted authority; and

transmitting the secure communication to a second user.

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

receiving the secure communication at an electronic hardware device of the second user; and

verifying the public signature key of the signing chip of the first user using a public signature key of the trusted authority.

3. The method of claim 2, wherein the certificate is embedded in the tamper-resistant memory of the signing chip of the first user prior to the electronic hardware device being provided to the first user.

4. The method of claim 3, wherein the public signature key of the trusted authority is embedded in a non-readable tamper-resistant memory of a signing chip of the electronic hardware device of the second user.

5. The method of claim 4, wherein the trusted authority is the manufacturer of the signing chip of the first user.

6. The method of claim 4, wherein public signature keys of a plurality of trusted authorities are embedded within the non-readable tamper-resistant memory of the signing chip of the second user.

7. The method of claim 1, further comprising the steps of;

generating a user specific public/private encryption/decryption key pair within the electronic hardware device of the first user; and

encrypting the secure communication using the private encryption key within the electronic hardware device of the first user.

8. The method of claim 7, wherein the public/private encryption/decryption key pair is generated using the RSA algorithm.

9. The method of claim 8, wherein the private signature key of the signing chip of the first user is generated using the DSA algorithm.

10. The method of claim 9, wherein the private signature key of the trusted authority is generated using the DSA algorithm.