Key conversion system and method

• US 20020071558A1
• Filed: 12/11/2000
• Published: 06/13/2002
• Est. Priority Date: 12/11/2000
• Status: Active Grant

• Current Assignee: WSOU Investments, LLC (WSOU Holdings, LLC)
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Patel, Sarvar
• Granted Patent: US 6,857,075 B2
• Time in Patent Office: Days
• US Class Current: 380/270
• CPC Class Codes: H04L 2209/12 Details relating to cryptographic hardware or logic circuitry
• CPC Class Codes: H04L 2209/80 Wireless network architectures or network communication protocols for wireless network security H04W12/00
• CPC Class Codes: H04L 2463/061 applying further key derivation, e.g. deriving traffic keys from a pair-wise master key cryptographic mechanisms or cryptographic arrangements for generation of secret information including derivation or calculation of cryptographic keys or passwords H04L9/0861
• CPC Class Codes: H04L 9/06 the encryption apparatus using shift registers or memories for block-wise or stream coding, e.g. DES systems or RC4; Hash functions; Pseudorandom sequence generators
• CPC Class Codes: H04L 9/0861 Generation of secret information including derivation or calculation of cryptographic keys or passwords
• CPC Class Codes: H04W 12/041 Key generation or derivation
• CPC Class Codes: H04W 36/1443 between licensed networks

Abstract

The present invention is a key conversion system for deterministically and reversibly converting a first key value of a first communications system into a second key value of a second communication system. For example, the key conversion system generates a first intermediate value from at least a portion of the first key value using a first random function. At least a portion of the first intermediate value is provided to a second random function to produce a second value. An exclusive-or is performed on at least a portion of the first key value and at least a portion of the second value to generate a second intermediate value. At least a portion of the second intermediate value is provided to a third random function to produce a third value. By performing an exclusive-or on at least a portion of the third value and at least a portion of the first intermediate value, the key conversion system produces at least a first portion of the second key value, and at least a second portion of the second key value is produced as the second intermediate value. The key conversion system is reversible or bi-directional in that, if the wireless unit is handed off back to the first communications system, the second key value of the second communications system is converted back to the first key value of the first communications system. For example, the key conversion system provides the at least second portion of the second key value to the third random function to produce the third value. The first intermediate value is generated by performing an exclusive-or on the first portion of the second key value and the third value. Using the second random function, the key conversion system generates the second value from the first intermediate value and produces at least a portion of the first key by performing an exclusive-or on the second value and the second portion of the second key value.

Claims

1. A method of converting a first key value for a first communications system to a second key value of a second communications, said method comprising:

generating a first intermediate value from at least a portion of said first key value using a first random function;

providing at least a portion of said first intermediate value to a second random function to produce a second value;

performing an exclusive-or on at least a portion of said first key value and at least a portion of said second value to generate a second intermediate value;

providing at least a portion of said second intermediate value to a third random function to produce a third value; and

producing at least a first portion of said second key value by performing an exclusive-or on at least a portion of said third value and at least a portion of said first intermediate value.

2. The method of claim 1 comprising:

producing at least a portion of said second intermediate value as at least a second portion of said second key value.

3. The method of claim 1 wherein said generating comprises the step of:

providing said first key value of m bits to a first random function to produce said first intermediate value of n-m bits.

4. The method of claim 3 wherein said first steps of providing and performing comprise:

providing said n-m bit first intermediate value to a second random function to produce an m bit second value; and

performing an exclusive-or on said m bit first key value and said m bit second value to generate said second intermediate value with m bits.

5. The method of claim 4 wherein said second step of providing and said step of producing comprise:

providing said m bit second intermediate value to a third random function to produce a n-m bit third value; and

performing an exclusive-or on said n-m bit third value and said n-m bit first intermediate value to generate an n-m bit portion of said second key value.

6. The method of claim 5 comprising:

providing said m bit second intermediate value as an m bit second portion of said second key value having n bits.

7. The method of claim 2 further comprising the steps of:

providing said second portion of said second key value to said third random function to produce said third value; and

generating said first intermediate value by subjecting said first portion of said second key value to an exclusive-or with said third value.

8. The method of claim 7 further comprises:

using said second random function to generate said second value from said first intermediate value; and

producing at least a portion of said first key by subjecting said second value to an exclusive-or with said second portion of said second key value.

9. The method of claim 6 further comprises:

providing said m bit first portion of said n bit second key value to said third random function to produce said n-m bit third value; and

generating said n-m bit first intermediate value using an exclusive-or of said n-m bit second portion of said n bit second key value with said n-m bit third value.

10. The method of claim 9 further comprises:

providing said n-m first intermediate value to said second random function to generate an m bit second value; and

producing said portion of said first key value having m bits by using an exclusive-or of said m bit first portion of said second key value with said m bit second value.

11. A key conversion system for converting a first key value for a first communications system to a second key value of a second communications, said system comprising:

processing circuitry adapted to generate a first intermediate value from at least a portion of said first key value using a first random function to provide at least a portion of said first intermediate value to a second random function to produce a second value, to perform an exclusive-or on at least a portion of said first key value and at least a portion of said second value to generate a second intermediate value, to provide at least a portion of said second intermediate value to a third random function to produce a third value and to produce at least a first portion of said second key value by subjecting at least a portion of said third value to an exclusive-or with at least a portion of said first intermediate value.

12. The system of claim 11 wherein said processing circuitry further configured to produce at least a portion of said second intermediate value as at least a second portion of said second key value.

13. The system of claim 12 wherein said processing circuitry further configured to provide said first key value of m bits to a first random function to produce said first intermediate value of n-m bits.

14. The system of claim 13 wherein said processing circuitry further configured to provide said n-m bit first intermediate value to a second random function to produce an m bit second value and to perform an exclusive-or on said m bit first key value and said m bit second value to generate said second intermediate value with m bits.

15. The system of claim 14 wherein said processing circuitry configured to provide said m bit second intermediate value to a third random function to produce a n-m bit third value and to perform an exclusive-or on said n-m bit third value and said n-m bit first intermediate value to generate an n-m bit portion of said second key value.

16. The system of claim 15 wherein said processing circuitry configured to provide said m bit second intermediate value as an m bit second portion of said second key value having n bits.

17. The system of claim 12 wherein said processing circuitry configured to provide said second portion of said second key value to said third random function to produce said third value and to generate said first intermediate value by subjecting said first portion of said second key value to an exclusive-or with said third value.

18. The system of claim 17 wherein said processing circuitry configured to use said second random function to generate said second value from said first intermediate value and produce at least a portion of said first key by subjecting said second value to an exclusive-or with said second portion of said second key value.

19. The system of claim 16 wherein said processing circuitry configured to provide said m bit first portion of said n bit second key value to said third random function to produce said n-m bit third value and to generate said n-m bit first intermediate value using an exclusive-or of said n-m bit second portion of said n bit second key value with said n-m bit third value.

20. The system of claim 19 wherein said processing circuitry is configured to provide said n-m first intermediate value to said second random function to generate an m bit second value and to produce said portion of said first key value having m bits by using an exclusive-or of said m bit first portion of said second key value with said m bit second value.