Method for creating and distributing cryptographic keys in a mobile radio system and corresponding mobile radio system

• US 20060171541A1
• Filed: 02/18/2004
• Published: 08/03/2006
• Est. Priority Date: 02/20/2003
• Status: Active Grant

• Current Assignee: Siemens AG
• Original Assignee: Siemens AG
• Inventors: Kroselberg, Dirk, Horn, Gunther
• Granted Patent: US 7,676,041 B2
• Time in Patent Office: Days
• US Class Current: 380/278
• CPC Class Codes: H04L 2209/80 Wireless network architectures or network communication protocols for wireless network security H04W12/00
• CPC Class Codes: H04L 63/062 for key distribution, e.g. centrally by trusted party cryptographic mechanisms or cryptographic arrangements for key distribution involving a central third party H04L9/0819
• CPC Class Codes: H04L 65/1016 IP multimedia subsystem [IMS]
• CPC Class Codes: H04L 65/1073 Registration or de-registration
• CPC Class Codes: H04L 9/0819 Key transport or distribution, i.e. key establishment techniques where one party creates or otherwise obtains a secret value, and securely transfers it to the other(s) network architectures or network communication protocols for key distribution in a packet data network H04L63/062
• CPC Class Codes: H04L 9/0838 Key agreement, i.e. key establishment technique in which a shared key is derived by parties as a function of information contributed by, or associated with, each of these network architectures or network communication protocols for key exchange in a packet data network H04L63/061
• CPC Class Codes: H04L 9/0869 involving random numbers or seeds
• CPC Class Codes: H04L 9/3273 for mutual authentication network architectures or network communication protocols for achieving mutual authentication in a packet data network H04L63/0869
• CPC Class Codes: H04W 12/041 Key generation or derivation
• CPC Class Codes: H04W 12/043 using a trusted network node as an anchor

Abstract

A first cryptographic key (318) and a second cryptographic key (322) are created by a mobile radio terminal (103) and by a computer of the home communications network (108, 109) by using authentication key materials (312). The first cryptographic key (318) is transmitted to the computer of the visited communications network (113), and the second cryptographic key (322) is transmitted to an application server computer (106, 107).

Claims

1. Method for creating and distributing cryptographic keys (318, 322) in a mobile radio system (100), which system has at least one mobile radio terminal (103), one first computer (113), one computer of a home communications network (109) and also one second computer (106, 107), whereby the mobile radio terminal (103) and the computer of the home communications network (109) contain authentication key materials (312, 314) resulting from an authentication, characterized in that

a first cryptographic key (318) and a second cryptographic key (322) are created by the mobile radio terminal (103) and by the computer of the home communications network (109) by using the authentication key materials (312),

the first cryptographic key (318) is transmitted to the first computer (113), and

the second cryptographic key (322) is transmitted to the second computer (106),

the first cryptographic key (318) and the second cryptographic key (322) are created in such a way that

no inference can be made from the first cryptographic key (318) as to the second cryptographic key (322),

no inference can be made from the second cryptographic key (322) as to the first cryptographic key (318),

no inference can be made from the first cryptographic key (318) or from the second cryptographic key (322) as to the authentication key materials (312, 314).

2. Method according to claim 1,

whereby the first computer (113) is a computer of a visited communications network, whereby the mobile radio terminal (103) is situated in the visited communications network (102), and

whereby the second computer is an application server computer (106, 107).

3. Method according to claim 1,

whereby the first computer (113) a first application server computer (106) and

whereby the second computer is a second application server computer (107).

4. Method according to claim 1, whereby the first cryptographic key (318) and the second cryptographic key (322) are created by using at least one key derivation function (317).

5. Method according to claim 1,

whereby the authentication key materials (312, 314) have at least two cryptographic keys.

6. Method according to claim 1,

whereby the mobile radio system (100) is designed as a mobile radio system based on a 3GPP standard.

7. Method according to claim 6,

whereby the mobile radio system (100) has an IP multimedia subsystem.

8. Method according to claim 1,

whereby the authentication key materials (312, 314) have an integrity key (314) and a transfer key (312).

9. Method according to claim 8,

whereby the first cryptographic key (318) and the second cryptographic key (322) are derived from the transfer key (312).

10. Method according to claim 1,

whereby additional cryptographic keys (323, 324) are created by the mobile radio terminal (103) and by the computer of the home communications network (109) for additional application server computers (107) by using the authentication key materials (312, 314) and are transmitted to the respective application server computers (107).

11. Method according to claim 1,

whereby the same key derivation function is used to create the cryptographic keys (318, 322, 323, 324).

12. Method according to claim 1,

whereby different additional input parameters (319) are used for the key derivation function (317) in order to create the cryptographic keys (318, 322, 323, 324).

13. Method according to claim 12,

whereby parameters created during authentication are used as additional input parameters (319) for the key derivation function (317).

14. Method according to claim 13,

whereby at least one of the previously created cryptographic keys (318, 322, 323, 324) are used as additional input parameters for the key derivation function.

15. Mobile radio system (100)

with at least one mobile radio terminal (103), in which authentication key materials (312, 314) resulting from an authentication are stored,

with one first computer (113),

with one computer of a home communications network (109) in which computer the authentication key materials (312, 314) resulting from an authentication are stored,

with at least one second computer (106, 107),

characterized in that

the mobile radio terminal (103) and the computer of the home communications network (109) each have a crypto unit for creating a first cryptographic key (318) and a second cryptographic key (322) by using the authentication key materials (312, 314), whereby the first cryptographic key (318) and the second cryptographic key (322) are created in such a way that

no inference can be made from the first cryptographic key (318) as to the second cryptographic key (322),

no inference can be made from the second cryptographic key (322) as to the first cryptographic key (318),

no inference can be made from the first cryptographic key (318) or from the second cryptographic key (322) as to the authentication key materials (312, 314),

the first computer (113) has a memory for storing the first cryptographic key (318), and

the second computer (106, 107) has a memory for storing the second cryptographic key (322).