Method and system of securely escrowing private keys in a public key infrastructure

• US 6,931,133 B2
• Filed: 09/03/2002
• Issued: 08/16/2005
• Est. Priority Date: 09/03/2002
• Status: Expired due to Term

• Current Assignee: DigiCert Incorporated
• Original Assignee: VeriSign, Inc.
• Inventors: Huang, Zhiyong, Ruan, Tom Qi Xiong, Andrews, Richard F.
• Primary Examiner(s): Barrón, Jr., Gilberto
• Assistant Examiner(s): Lanier, Benjamin E.
• Application Number:
  US10/232,624
• Publication Number:
  US 20040042620A1
• Time in Patent Office: 1,078 Days
• Field of Search: 380/286
• US Class Current: 380/286
• CPC Class Codes: H04L 2209/04 Masking or blinding
• CPC Class Codes: H04L 9/0894 Escrow, recovery or storing of secret information, e.g. secret key escrow or cryptographic key storage

Abstract

A method of restricting access to private keys in a public key infrastructure provides for storage of an encrypted private key at a primary site. A masked session key is stored at a secondary site, where the masked session key enables recovery of the private key. By using distributed storage architecture for recovery data, simplification can be achieved without sacrificing security.

Claims

1. A method for escrowing a private key in a public key infrastructure, comprising:

creating a key pair including a private key and a public key;

creating a session key;

encrypting the private key using the session key;

creating a session key mask;

storing the encrypted private key and the session key mask;

creating a masked session key by exclusive-ORing the session key and the session key mask;

deleting the session key; and

sending the masked session key and a digital certificate to a secondary site.

2. The method of claim 1, further comprising:

sending a key recovery request, including the digital certificate, to the secondary site;

receiving the masked session key from the secondary site;

recreating the session key by exclusive-ORing the masked session key and the session key mask; and

recovering the private key by decrypting the encrypted private key using the recreated session key.

3. The method of claim 1, wherein the session key is a symmetric key.

4. The method of claim 1, wherein said creating the session key includes using a triple-data encryption standard and an initialization vector.

5. The method of claim 1, wherein the session mask is a random string having a bit-length equal to the session key.

6. The method of claim 1, wherein the session mask is a pseudo-random string having a bit-length equal to the session key.

7. The method of claim 2, wherein the key recovery request includes a plurality of digital certificates.

8. The method of claim 2, further comprising:

combining the decrypted private key with a corresponding key pair certificate.

9. The method of claim 2, further comprising:

creating an audit trail at the secondary site associated with the key recovery request.

10. A computer readable medium including instructions adapted to be executed by a processor to perform a method for escrowing a private key in a public key infrastructure, the method comprising:

creating a key pair including a private key and a public key;

creating a session key;

encrypting the private key using the session key;

creating a session key mask;

storing the encrypted private key and the session key mask;

creating a masked session key by exclusive-ORing the session key and the session key mask;

deleting the session key; and

sending the masked session key and a digital certificate to a secondary site.

11. The computer readable medium of claim 10, wherein the method further comprises:

sending a key recovery request, including the digital certificate, to the secondary site;

receiving the masked session key from the secondary site;

recreating the session key by exclusive-ORing the masked session key and the session key mask; and

recovering the private key by decrypting the encrypted private key using the recreated session key.

12. The computer readable medium of claim 10, wherein the session key is a symmetric key.

13. The computer readable medium of claim 10, wherein said creating the session key includes using a triple-data encryption standard and an initialization vector.

14. The computer readable medium of claim 10, wherein the session mask is a random string having a bit-length equal to the session key.

15. The computer readable medium of claim 10, wherein the session mask is a pseudo-random string having a bit-length equal to the session key.

16. The computer readable medium of claim 11, wherein the key recovery request includes a plurality of digital certificates.

17. The computer readable medium of claim 11, wherein the method further comprises:

combining the decrypted private key with a corresponding key pair certificate.

18. The computer readable medium of claim 11, wherein the method further comprises:

creating an audit trail at the secondary site associated with the key recovery request.

19. A system for escrowing a private key in a public key infrastructure, comprising:

a secondary site, coupled to the network, including a secondary database and a control center; and

a primary site, coupled to a network, including a primary database and a key management server, adapted to;

create a key pair including a private key and a public key,

create a session key,

encrypt the private key using the session key,

create a session key mask,

store the encrypted private key and the session key mask in the primary database,

create a masked session key by exclusive-ORing the session key and the session key mask,

delete the session key, and

send the masked session key and a digital certificate to the secondary site for storage within the secondary database.

20. The system of claim 19, wherein the primary site is further adapted to:

send a key recovery request, including the digital certificate, to the secondary site;

receive the masked session key from the secondary site;

recreate the session key by exclusive-ORing the masked session key and the session key mask; and

recover the private key by decrypting the encrypted private key using the recreated session key.

21. The system of claim 19, wherein the session key is a symmetric key.

22. The system of claim 19, wherein said creating the session key includes using a triple-data encryption standard and an initialization vector.

23. The system of claim 19, wherein the session mask is a random string having a bit-length equal to the session key.

24. The system of claim 19, wherein the session mask is a pseudo-random string having a bit-length equal to the session key.

25. The system of claim 20, wherein the key recovery request includes a plurality of digital certificates.

26. The system of claim 20, wherein the primary site is further adapted to:

combine the decrypted private key with a corresponding key pair certificate.