Lightweight public key infrastructure employing unsigned certificates

• US 7,269,726 B1
• Filed: 01/14/2000
• Issued: 09/11/2007
• Est. Priority Date: 01/14/2000
• Status: Expired due to Term

• Current Assignee: Hewlett Packard Enterprise Development LP (Hewlett-Packard Enterprise Company)
• Original Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Inventors: Corella, Francisco
• Primary Examiner(s): Barron, Jr.; Gilberto
• Assistant Examiner(s): BROWN, CHRISTOPHER J
• Application Number:
  US09/483,186
• Time in Patent Office: 2,797 Days
• Field of Search: 713/169, 713/156, 726/10, 726/18
• US Class Current: 713/156
• CPC Class Codes: H04L 2209/56 Financial cryptography, e.g. electronic payment or e-cash
• CPC Class Codes: H04L 2209/805 Lightweight hardware, e.g. radio-frequency identification [RFID] or sensor
• CPC Class Codes: H04L 9/006 involving public key infrastructure [PKI] trust models network architecture or network communication protocol for supporting authentication of entities using certificates in a packet data network H04L63/0823
• CPC Class Codes: H04L 9/3236 using cryptographic hash functions
• CPC Class Codes: H04L 9/3268 using certificate validation, registration, distribution or revocation, e.g. certificate revocation list [CRL]

Abstract

A public key infrastructure (PKI) includes a subject, a verifier, and certificate authority that issues a first unsigned certificate to the subject that binds a public key of the subject to long-term identification information related to the subject and maintains a certificate database of unsigned certificates in which it stores the first unsigned certificate. The verifier maintains a hash table containing cryptographic hashes of valid unsigned certificates corresponding to the unsigned certificates stored in the certificate database and including a cryptographic hash of the first unsigned certificate. The subject presents the issued first unsigned certificate to the verifier for authentication and demonstrates that the subject has knowledge of a private key corresponding to the public key in the unsigned certificate.

Claims

1. A public key system comprising:

a subject;

a certificate authority issuing a first certificate to the subject, the first certificate including a public key of the subject, long-term identification information related to the subject, and meta-data related to the first certificate, wherein the first certificate is not signed by the certificate authority, the certificate authority maintaining a database of records representing issued certificates in which it stores a record representing the first certificate, wherein the issued certificates are each not signed by the certificate authority and are each valid until at least one of revoked by the certificate authority and expired; and

a verifier maintaining a hash table containing cryptographic hashes of valid certificates corresponding to the records stored in the database and including a cryptographic hash of the first certificate, wherein the subject presents the issued first certificate to the verifier for authentication and demonstrates that the subject has knowledge of a private key corresponding to the public key in the first certificate.

2. The public key system of claim 1 wherein the first certificate includes an expiration date/time.

3. The public key system of claim 1 wherein the first certificate does not include an expiration date/time.

4. The public key system of claim 1 wherein the private key is stored in a smartcard accessible by the subject.

5. The public key system of claim 1 wherein the private key is stored in a secure software wallet accessible by the subject.

6. The public key system of claim 1 wherein the verifier computes the cryptographic hash of the first certificate with a collision-resistant hash function.

7. The public key system of claim 6 wherein the collision-resistant hash function is a SHA-1 hash function.

8. The public key system of claim 6 wherein the collision-resistant hash function is a MD5 hash function.

9. The public key system of claim 1 wherein the certificate authority and the verifier operate to revoke the first certificate when at least a portion of the long-term identification information related to the subject no longer applies to the subject.

10. The public key system of claim 1 wherein the certificate authority and the verifier perform a revocation protocol to revoke the first certificate when at least one of the private key is comprised and at least a portion of the long-term identification information related to the subject no longer applies to the subject, the revocation protocol including:

the certificate authority retrieving a record representing the first certificate from the database and obtaining a cryptographic hash of the first certificate;

the certificate authority sending a message to verifier containing the cryptographic hash of the first certificate and requesting that the verifier remove the corresponding cryptographic hash of the first certificate from its hash table;

the verifier removing the cryptographic hash of the first certificate from its hash table and notifying the certificate authority that it has removed the cryptographic hash of the first certificate from its hash table; and

the certificate authority collecting the notification sent by the verifier.

11. The public key system of claim 10 wherein the revocation protocol includes the certificate authority marking the record of the first certificate in the database as being invalid, for auditing purposes.

12. The public key system of claim 10 wherein the revocation protocol includes the certificate authority deleting the record representing the first certificate from the database.

25. The public key system of claim 1 wherein the meta-data includes at least one of a serial number of the first certificate and a name of the certificate authority.

26. The public key system of claim 1 wherein the long-term identification information related to the subject includes at least one of the subjects'"'"' name and a number identifying the subject.

27. The public key system of claim 1 wherein the certificate authority and the verifier operate to revoke the first certificate when the private key corresponding to the public key in the first certificate is compromised.

13. A method of authenticating a subject to a verifier in a public key system, the method comprising the steps of:

issuing a first certificate from a certificate authority to the subject, the first certificate including a public key of the subject, long-term identification information related to the subject, and meta-data related to the first certificate, wherein the first certificate is not signed by the certificate authority;

maintaining, at the certificate authority, a database of records representing issued certificates that are each not singed by the certificate authority and are each valid until at least one of revoked by the certificate authority and expired;

storing a record representing the first certificate in the database;

maintaining, at the verifier, a hash table containing cryptographic hashes of valid certificates corresponding to the records stored in the database and including a cryptographic hash of the first certificate;

presenting the issued first certificate from the subject to the verifier for authentication;

demonstrating, by the subject, that the subject has knowledge of a private key corresponding to the public key in the first certificate.

14. The method of claim 13 wherein the first certificate includes an expiration date/time.

15. The method of claim 13 wherein the first certificate does not include an expiration date/time.

16. The method of claim 13 further comprising the step of:

storing the private key in a smartcard accessible by the subject.

17. The method of claim 13 further comprising the step of:

storing the private key in a secure software wallet accessible by the subject.

18. The method of claim 13 further comprising the step of:

computing, by the verifier, the cryptographic hash of the first certificate with a collision-resistant hash function.

19. The method of claim 18 wherein the collision-resistant hash function is a SHA-1 hash function.

20. The method of claim 18 wherein the collision-resistant hash function is a MD5 hash function.

21. The method of claim 13 further comprising the step of:

revoking the first certificate when at least a portion of the long-term identification information related to the subject no longer applies to the subject.

22. The method of claim 13 further comprising revoking the first certificate when at least one of the private key is comprised and at least a portion of the long-term identification information related to the subject no longer applies to the subject, the revoking including:

retrieving the record representing the first certificate from the certificate database and obtaining a cryptographic hash of the first certificate;

sending a message from certificate authority to verifier containing the cryptographic hash of the first certificate;

requesting that the verifier remove the corresponding cryptographic hash of the first certificate from its hash table;

removing the cryptographic hash of the first certificate from the hash table;

notifying the certificate authority that the cryptographic hash of the first certificate is removed from the hash table; and

collecting, at the certificate authority, the notification sent in the notifying step.

23. The method of claim 22 wherein the revoking step further includes:

marking the record representing the first certificate in the database as being invalid, for auditing purposes.

24. The method of claim 22 wherein the revoking step further includes:

deleting the record representing the first certificate from the database.

28. The method of claim 13 further comprising:

revoking the first certificate when the private key corresponding to the public key in the first certificate is compromised.