Cryptographic key backup and escrow system

• US 20050138374A1
• Filed: 12/21/2004
• Published: 06/23/2005
• Est. Priority Date: 12/23/2003
• Status: Active Grant

• Current Assignee: Wells Fargo Bank NA (Wells Fargo & Company)
• Original Assignee: Wachovia Corporation (Wells Fargo & Company)
• Inventors: Badia, David Victor, Kauer, Neil Kevin, Zheng, Yuliang
• Granted Patent: US 8,139,770 B2
• Time in Patent Office: Days
• US Class Current: 713/166
• CPC Class Codes: H04L 9/0894 Escrow, recovery or storing of secret information, e.g. secret key escrow or cryptographic key storage

Abstract

A system for securely storing application keys is comprised of a database system, a peripheral hardware security module and cryptographic keys, wherein cryptographic keys comprise application keys, intermediate keys and a master key. Application keys are grouped according to characteristic and are associated with a particular intermediate key, which is utilized to scramble and descramble application keys within the associated group. Intermediate keys are associated with the master key, which is utilized to scramble and descramble the intermediate keys. Scrambling and descrambling of keys is performed within the peripheral hardware security module.

Claims

1. In a networked computer system, a method for verifying an encrypted cryptographic key, comprising:

(a) providing a lower-level cryptographic key;

(b) providing a higher-level cryptographic key having an encryption portion and a verification portion;

(c) utilizing the encryption portion of the higher-level cryptographic key, encrypting the lower-level cryptographic key;

(d) utilizing the verification portion of the higher-level cryptographic key, generating a verification tag for storing with the encrypted lower-level cryptographic key; and

(e) utilizing the verification portion of the higher-level cryptographic key, verifying the integrity of the encrypted lower-level cryptographic key by examining the verification tag stored with the encrypted lower-level cryptographic key.

2. The method for verifying an encrypted cryptographic key of claim 1, wherein the lower-level cryptographic key is an application key and the higher-level cryptographic key is an intermediate key.

3. The method for verifying an encrypted cryptographic key of claim 2, wherein the intermediate key is encrypted with a master key.

4. The method for verifying an encrypted cryptographic key of claim 1, wherein the lower-level cryptographic key is an intermediate key and the higher-level cryptographic key is a master key.

5. The method for verifying an encrypted cryptographic key of claim 4, wherein the intermediate key is utilized to encrypt an application key.

6. The method for verifying an encrypted cryptographic key of claim 4, wherein the intermediate key includes a verification portion and an encryption portion.

7. The method for verifying an encrypted cryptographic key of claim 1, wherein the lower-level cryptographic key is not decrypted during the verifying step.

8. In a key management system, a method of accessing at least a portion of an encrypted cryptographic key, comprising:

(a) providing a lower-level cryptographic key and a higher-level cryptographic key, at least the lower-level cryptographic key having an encryption portion and a verification portion;

(b) utilizing at least a first portion of the higher-level cryptographic key, encrypting the encryption portion and verification portion of the lower-level cryptographic key, wherein the encryption portion is encrypted independently of the verification portion; and

(c) utilizing the at least first portion of the higher-level cryptographic key, decrypting the encrypted verification portion of the lower-level cryptographic key independently of decrypting the encrypted encryption portion of the lower-level cryptographic key.

9. The method of accessing at least a portion of an encrypted cryptographic key of claim 8, wherein the lower-level cryptographic key is an intermediate key and the higher-level cryptographic key is a master key.

10. The method of accessing at least a portion of an encrypted cryptographic key of claim 8, wherein the encrypted encryption portion of the lower-level cryptographic key is decrypted at a substantially different time than the encrypted verification portion of the lower-level cryptographic key is decrypted.

11. The method of accessing at least a portion of an encrypted cryptographic key of claim 10, wherein the encrypted verification portion of the lower-level cryptographic key is decrypted in order to generate a verification tag for an application key.

12. The method of accessing at least a portion of an encrypted cryptographic key of claim 10, wherein the encrypted verification portion of the lower-level cryptographic key is decrypted in order to verify the integrity of an application key.

13. The method of accessing at least a portion of an encrypted cryptographic key of claim 8, wherein the encrypted verification portion of the lower-level cryptographic key is decrypted at a substantially different time than the encrypted encryption portion of the lower-level cryptographic key is decrypted.

14. The method of accessing at least a portion of an encrypted cryptographic key of claim 13, wherein the encrypted encryption portion of the lower-level cryptographic key is decrypted in order to encrypt an application key.

15. The method of accessing at least a portion of an encrypted cryptographic key of claim 13, wherein the encrypted encryption portion of the lower-level cryptographic key is decrypted in order to decrypt an application key.

16. The method of accessing at least a portion of an encrypted cryptographic key of claim 8, wherein the steps are repeated cyclically as a part of a user-defined integrity management process.

17. The method of accessing at least a portion of an encrypted cryptographic key of claim 16, wherein the verification portion of the lower-level cryptographic key is accessed on a more frequent schedule than is the encryption portion of the lower-level cryptographic key.

18. The method of accessing at least a portion of an encrypted cryptographic key of claim 8, wherein the higher-level cryptographic key has an encryption portion and a verification portion.

19. The method of accessing at least a portion of an encrypted cryptographic key of claim 18, additionally comprising:

(a) utilizing the verification portion of the higher-level cryptographic key, generating a verification tag for storing with the encrypted lower-level cryptographic key; and

(b) utilizing the verification portion of the higher-level cryptographic key, verifying the integrity of the encrypted lower-level cryptographic key by examining the verification tag of the encrypted lower-level cryptographic key prior to decrypting any portion of the encrypted lower-level cryptographic key.

20. In a networked computer system, a method for managing stored cryptographic keys, comprising:

(a) receiving a plurality of lower-level cryptographic keys and higher-level cryptographic keys and storing them in a database system;

(b) in the database system, organizing the lower-level cryptographic keys into groups according to a defined characteristic;

(c) after organizing the keys, receiving a new lower-level cryptographic key and sorting the new lower-level cryptographic key into groups according to a corresponding characteristic of the new lower-level cryptographic key; and

(d) designating a separate higher-level cryptographic key for performing scrambling and descrambling processes on lower-level cryptographic keys within each group.

21. In a networked computer system, the method for managing stored cryptographic keys of claim 20, wherein the number of lower-level cryptographic keys is independent of the number of higher-level cryptographic keys.

22. In a networked computer system, the method for managing stored cryptographic keys of claim 20, wherein the lower-level cryptographic keys and higher-level cryptographic keys are refreshed cyclically.

23. In a networked computer system, the method for managing stored cryptographic keys of claim 22, further comprising rotating a selected one of the higher-level cryptographic keys, wherein rotating includes refreshing the selected higher-level cryptographic key, decrypting all lower-level cryptographic keys in the group associated with the selected higher-level cryptographic key and re-encrypting the lower-level cryptographic keys in the associated group with the new higher-level cryptographic key without altering the clear forms of the lower-level cryptographic keys in the associated group.

24. In a networked computer system, the method for managing stored cryptographic keys of claim 22, wherein the lower-level cryptographic keys are refreshed independently of the higher-level cryptographic keys.

25. In a networked computer system, the method for managing stored cryptographic keys of claim 20, wherein the defined grouping characteristic for lower-level cryptographic keys is the encryption algorithm for which a lower-level cryptographic key is utilized.

26. In a networked computer system, the method for managing stored cryptographic keys of claim 20, wherein the defined grouping characteristic for lower-level cryptographic keys is the business unit for which a lower-level cryptographic key is utilized.

27. In a networked computer system, a method for managing and maintaining security of cryptographic keys, comprising:

(a) providing a lower-level cryptographic key and a higher-level cryptographic key;

(b) utilizing the higher-level cryptographic key to encrypt the lower-level cryptographic key; and

(c) rotating the higher-level cryptographic key, wherein rotating includes refreshing the higher-level cryptographic key, decrypting the lower-level cryptographic key with the higher-level cryptographic key and re-encrypting the lower-level cryptographic key with the new higher-level cryptographic key without altering the clear form of the lower-level cryptographic key.

28. In a networked computer system, the method for managing and maintaining security of cryptographic keys of claim 27, wherein the lower-level cryptographic key is an application key and the higher-level cryptographic key is an intermediate key.

29. In a networked computer system, the method for managing and maintaining security of cryptographic keys of claim 27, wherein the lower-level cryptographic key is an intermediate key and the higher-level cryptographic key is a master key.

30. In a networked computer system, the method for managing and maintaining security of cryptographic keys of claim 27, wherein the lower-level cryptographic key is a first intermediate key and the higher-level cryptographic key is a second intermediate key.

31. In a networked computer system, the method for managing and maintaining security of cryptographic keys of claim 27, wherein the higher-level cryptographic key is automatically rotated cyclically.

32. A secure key escrow system for application keys within a networked computer system, comprising:

(a) a collection of key data, the key data including a plurality of application keys, at least one level of intermediate keys and a master key, the application keys for use in facilitating secure communication in the networked computer system, wherein each application key is encrypted using a key from the lowest of the at least one level of intermediate keys, and each key in the highest of the at least one level of intermediate keys is encrypted using the master key;

(b) a cryptographic key database system that stores the encrypted application keys and each key from at least the lowest level of intermediate keys;

(c) a server computer communicatively connected into the networked computer system and arranged to provide application keys from the database system to other computers in the networked computer system; and

(d) a peripheral hardware security module communicatively connected to the server computer that encrypts each application key using a key from the lowest level of the at least one level of intermediate keys and encrypts each intermediate key from the highest level of the at least one level of intermediate keys with the master key.

33. The secure key escrow system for application keys within a networked computer system of claim 32, wherein there is one key at each level of the at least one level of intermediate keys.

34. The secure key escrow system for application keys within a networked computer system of claim 32, wherein the lowest level of the at least one level of intermediate keys and the highest level of the at least one level of intermediate keys are the same level.

35. The secure key escrow system for application keys within a networked computer system of claim 34, wherein there is one key at each level of the at least one level of intermediate keys.

36. The secure key escrow system for application keys within a networked computer system of claim 32, wherein the database system includes a first database housing the encrypted application keys and each key from at least the lowest level of intermediate keys, and a second database mirroring the first database.

37. The secure key escrow system for application keys within a networked computer system of claim 32, further comprising a second peripheral hardware security module adapted to perform the same functionality as the first peripheral hardware security module and using the same master key for backup.

38. The secure key escrow system for application keys within a networked computer system of claim 32, wherein the collection of key data includes a separate verification tag associated with each encrypted application key and encrypted intermediate key, each separate verification tag associated with an encrypted application key being generated using a key from the lowest of the at least one level of intermediate keys, each separate verification tag associated with an intermediate key in the highest of the at least one level of intermediate keys being generated using the master key.

39. The secure key escrow system for application keys within a networked computer system of claim 32, further comprising a plurality of master key shares, the plurality of master key shares being generated by mathematically splitting the master key.

40. The secure key escrow system for application keys within a networked computer system of claim 39, wherein each of the plurality of master key shares is stored on a portable device.

41. The secure key escrow system for application keys within a networked computer system of claim 40, wherein each portable device is password protected.

42. A method for operating a secure key escrow system for application keys within a networked computer system, comprising:

(a) collecting key data, the key data including a plurality of application keys, at least one level of intermediate keys and a master key, the application keys for use in facilitating secure communication in the networked computer system, wherein each application key is encrypted using a key from the lowest of the at least one level of intermediate keys, and each key in the highest of the at least one level of intermediate keys is encrypted using the master key;

(b) utilizing a cryptographic key database system, storing encrypted application keys and each key from at least the lowest level of intermediate keys in;

(c) utilizing a server computer communicatively connected with the networked computer system, providing application keys from the database system to other computers in the networked computer system; and

(d) utilizing a peripheral hardware security module communicatively connected to the server computer, encrypting each application key using a key from the lowest level of the at least one level of intermediate keys and encrypting each intermediate key from the highest level of the at least one level of intermediate keys with the master key.

43. The method for operating a secure key escrow system for application keys within a networked computer system of claim 42, further comprising:

utilizing a mathematical algorithm, splitting the master key into a plurality of master key shares.

44. The method for operating a secure key escrow system for application keys within a networked computer system of claim 43, further comprising:

storing each master key share on a portable device and distributing each portable device to an entity.

45. The method for operating a secure key escrow system for application keys within a networked computer system of claim 44, further comprising:

utilizing the peripheral hardware security module, reconstructing the master key from the plurality of master key shares.

46. The method for operating a secure key escrow system for application keys within a networked computer system of claim 45, wherein less than all of the plurality of master key shares are utilized to reconstruct the master key.