Method and apparatus for generating large numbers of encryption keys

• US 8,594,323 B2
• Filed: 09/21/2004
• Issued: 11/26/2013
• Est. Priority Date: 09/21/2004
• Status: Expired due to Fees

• Current Assignee: RPX Clearinghouse LLC (RPX Corporation)
• Original Assignee: Rockstar Consortium US LP (Rockstar Consortium Inc.)
• Inventors: Dondeti, Lakshminath
• Primary Examiner(s): Yalew, Fikremariam A
• Application Number:
  US10/946,322
• Publication Number:
  US 20060062384A1
• Time in Patent Office: 3,353 Days
• Field of Search: 380/44, 380/47, 380/278, 380/283, 713/163, 713/171
• US Class Current: 380/44
• CPC Class Codes: H04L 9/065 Encryption by serially and continuously modifying data stream elements, e.g. stream cipher systems, RC4, SEAL or A5/3
• CPC Class Codes: H04L 9/0816 Key establishment, i.e. cryptographic processes or cryptographic protocols whereby a shared secret becomes available to two or more parties, for subsequent use
• CPC Class Codes: H04L 9/0841 involving Diffie-Hellman or related key agreement protocols
• CPC Class Codes: H04L 9/0869 involving random numbers or seeds

Abstract

Entropy obtained from a series of key generation exchanges may be combined with entropy from a strong entropy source to allow the strong entropy to be stretched to generate a larger number of keys for use on a communication network, without requiring additional information from the group members and without requiring the entropy source to be increased in size or in number. In one embodiment, nonces exchanged during an initial key exchange are used to generate additional key material that is then fed, together with a fresh random secret, to another pseudo-random function to generate an additional key stream. The fresh ransom secret may be generated at the GCKS from a physical entropy source or other entropy source, and may be changed at will by the GCKS to further increase the strength of the keys. The methods are particularly useful for group key management where a large number of keys are required to be generated in a short time frame.

Claims

1. A method of generating encryption keys, the method comprising:

obtaining, by a computer processor environment, first information associated with a first key exchange session from a first group member;

generating, by the computer processor environment from the first information, a first set of keys for the first group member and first additional pseudo-random information not for use by the first group member;

obtaining, by the computer processor environment, second information associated with a second key exchange session from a second group member;

generating, by the computer processor environment from the second information, a second set of keys for the second group member and second pseudo-random information not for use by the second group member; and

combining, by the computer processor environment, the first additional pseudo-random information and second additional pseudo-random information with a fresh random secret to stretch the fresh random secret to enable additional encryption keys to be generated from the fresh random secret.

2. The method of claim 1, wherein the first additional pseudo-random information not for use by the first group member is obtained in connection with participating in a first key exchange procedure with the first group member, said first key exchange procedure comprising exchanging first nonces and Diffie-Hellman values, generating a first seedkey from the first nonces and Diffie-Hellman values, and using the first seedkey to generate the first set of keys for the first group member and first additional pseudo-random information not for use by the first group member.

3. The method of claim 2, wherein the first seedkey is used as input to a first pseudo-random function to generate a first stream of pseudo-random information, a first portion of said first stream of pseudo-random information being used to form the first set of encryption keys and a second portion of said first stream of pseudo-random information being used to form the first additional pseudo-random information not for use by the first group member.

4. The method of claim 3, wherein the second additional pseudo-random information not for use by the second group member is obtained in connection with participating in a second key exchange procedure with the second group member, said second key exchange procedure comprising exchanging second nonces and Diffie-Hellman values, generating a second seedkey from the second nonces and Diffie-Hellman values, and using the second seedkey to generate the second set of keys for the second group member and second additional pseudo-random information not for use by the second group member.

5. The method of claim 4, wherein the second seedkey is used as input to the first pseudo-random function to generate a second stream of pseudo-random information, a first portion of said second stream of pseudo-random information being used to form the second set of encryption keys and a second portion of said second stream of pseudo-random information being used to form the second additional pseudo-random information not for use by the first group member.

6. The method of claim 5, wherein combining the first additional pseudo-random information and second additional pseudo-random information with the fresh random secret is performed using a second pseudo-random function, the second pseudo-random function being different than the first pseudo-random function.

7. The method of claim 1, further comprising:

obtaining additional information associated with other key exchange sessions from other group members; and

generating, from the additional information, sets of keys for the other group members and additional pseudo-random information not for use by the other group members; and

wherein combining the first additional pseudo-random information and second additional pseudo-random information further comprises combining the first and second additional pseudo-random information with the additional pseudo-random information not for use by the other group members with the fresh random secret to stretch the fresh random secret to enable additional encryption keys to be generated from the fresh random secret.

8. The method of claim 1, further comprising changing the fresh random secret from a first fresh random secret to a second fresh random secret.

9. The method of claim 8, wherein the second fresh random secret is generated by a physical entropy source.

10. A Group Controller Key Server (GCKS), comprising:

a tangible non-transitory computer readable storage medium containing program logic code stored thereon which, when loaded into a processor environment of the GCKS, causes the GCKS to implement a method of generating encryption keys, the method comprising;

obtaining first information associated with a first key exchange session from a first group member;

generating, from the first information, a first set of keys for the first group member and first additional pseudo-random information not for use by the first group member;

obtaining second information associated with a second key exchange session from a second group member;

generating, from the second information, a second set of keys for the second group member and second pseudo-random information not for use by the second group member; and

combining the first additional pseudo-random information and second additional pseudo-random information with a fresh random secret to stretch the fresh random secret to enable additional encryption keys to be generated from the fresh random secret.

11. The GCKS of claim 10, wherein the first additional pseudo-random information not for use by the first group member is obtained in connection with participating in a first key exchange procedure with the first group member, said first key exchange procedure comprising exchanging first nonces and Diffie-Hellman values, generating a first seedkey from the first nonces and Diffie-Hellman values, and using the first seedkey to generate the first set of keys for the first group member and first additional pseudo-random information not for use by the first group member.

12. The GCKS of claim 11, wherein the first seedkey is used as input to a first pseudo-random function to generate a first stream of pseudo-random information, a first portion of said first stream of pseudo-random information being used to form the first set of encryption keys and a second portion of said first stream of pseudo-random information being used to form the first additional pseudo-random information not for use by the first group member.

13. The GCKS of claim 12, wherein the second additional pseudo-random information not for use by the second group member is obtained in connection with participating in a second key exchange procedure with the second group member, said second key exchange procedure comprising exchanging second nonces and Diffie-Hellman values, generating a second seedkey from the second nonces and Diffie-Hellman values, and using the second seedkey to generate the second set of keys for the second group member and second additional pseudo-random information not for use by the second group member.

14. The GCKS of claim 13, wherein the second seedkey is used as input to the first pseudo-random function to generate a second stream of pseudo-random information, a first portion of said second stream of pseudo-random information being used to form the second set of encryption keys and a second portion of said second stream of pseudo-random information being used to form the second additional pseudo-random information not for use by the first group member.

15. The GCKS of claim 14, wherein combining the first additional pseudo-random information and second additional pseudo-random information with the fresh random secret is performed using a second pseudo-random function, the second pseudo-random function being different than the first pseudo-random function.

16. The GCKS of claim 10, wherein the method further comprises:

obtaining additional information associated with other key exchange sessions from other group members; and

generating, from the additional information, sets of keys for the other group members and additional pseudo-random information not for use by the other group members; and

wherein combining the first additional pseudo-random information and second additional pseudo-random information further comprises combining the first and second additional pseudo-random information with the additional pseudo-random information not for use by the other group members with the fresh random secret to stretch the fresh random secret to enable additional encryption keys to be generated from the fresh random secret.

17. The GCKS of claim 10, wherein the method further comprises changing the fresh random secret from a first fresh random secret to a second fresh random secret.

18. The GCKS of claim 17, wherein the second fresh random secret is generated by a physical entropy source.