CIPHER KEY GENERATION IN COMMUNICATION SYSTEM
Techniques are disclosed for generating a cipher key such that an encryption algorithm typically usable in accordance with a first security context can be used in accordance with a second security context. In one example, the first security context is a UMTS security context and the second security context is a GSM security context.
1 . A method, comprising:
generating a first cipher key of an encryption algorithm for use by at least one computing device in a communication network to exchange encrypted communications with at least another computing device in the communication network, the first cipher key being associated with a security context of a first communication mode and being generated from a second cipher key associated with a security context of a second communication mode, wherein the first cipher key is usable in the encryption algorithm in accordance with the second communication mode.
2 . The method of claim 1 , wherein the security context of the first communication mode is a Universal Mobile Telecommunications System (UMTS) security context.
3 . The method of claim 1 , wherein the security context of the second communication mode is a Global System for Mobile Communication (GSM) security context.
4 . The method of claim 1 , wherein the encryption algorithm is an encryption algorithm that utilizes a 128-bit cipher key.
5 . The method of claim 1 , wherein the first cipher key comprises a 128-bit cipher key.
6 . The method of claim 1 , wherein the second cipher key comprises a 64-bit cipher key.
7 . The method of claim 1 , wherein the generating step further comprises the at least one computing device:
obtaining the second cipher key;
generating a pair of key components from the second cipher key; and
generating the first cipher key from the pair of key components.
8 . The method of claim 7 , wherein the pair of key components comprise an integrity key (IK) and another cipher key (CK).
9 . The method of claim 1 , wherein the generating step further comprises the at least one computing device:
obtaining the second cipher key; and
generating the first cipher key by concatenating one instance of the second cipher key to another instance of the second cipher key.
10 . The method of claim 1 , wherein the at least one computing device generates the first cipher key.
11 . The method of claim 10 , wherein the at least one computing device comprises a mobile station in the communication network.
12 . The method of claim 1 , wherein another computing device in the communication network generates the first cipher key.
13 . The method of claim 12 , wherein the other computing device comprises a visiting location register.
14 . The method of claim 12 , wherein the other computing device comprises a mobile switching center.
15 . The method of claim 1 , wherein the second cipher key is derived from a nonce and a previously established cipher key that is equivalent to the second cipher key.
16 . The method of claim 15 , wherein the previously established cipher key that is equivalent to the second cipher key is generated as part of an authentication process.
17 . The method of claim 16 , wherein the previously established cipher key that is equivalent to the second cipher key is generated at a home location register.
18 . An apparatus, comprising:
a memory associated with at least one computing device; and
a processor associated with the at least one computing device, coupled to the memory, and configured to generate a first cipher key of an encryption algorithm for use by the at least one computing device in a communication network to exchange encrypted communications with at least another computing device in the communication network, the first cipher key being associated with a security context of a first communication mode and being generated from a second cipher key associated with a security context of a second communication mode, wherein the first cipher key is usable in the encryption algorithm in accordance with the second communication mode.
19 . The apparatus of claim 18 , wherein the security context of the first communication mode is a Universal Mobile Telecommunications System (UMTS) security context.
20 . The apparatus of claim 18 , wherein the security context of the second communication mode is a Global System for Mobile Communication (GSM) security context.
21 . The apparatus of claim 18 , wherein the encryption algorithm is an encryption algorithm that utilizes a 128-bit cipher key.
22 . The apparatus of claim 18 , wherein the first cipher key comprises a 128-bit cipher key and the second cipher key comprises a 64-bit cipher key.
23 . The apparatus of claim 18 , wherein the generating step further comprises the processor:
obtaining the second cipher key;
generating a pair of key components from the second cipher key; and
generating the first cipher key from the pair of key components.
24 . The apparatus of claim 18 , wherein the generating step further comprises the processor:
obtaining the second cipher key; and
generating the first cipher key by concatenating one instance of the second cipher key to another instance of the second cipher key.
25 . A computing device in a communication network, comprising:
a memory; and
a processor coupled to the memory and configured to generate a 128-bit cipher key of an encryption algorithm for use by the computing device to exchange encrypted communications with at least another computing device in the communication network, the 128-bit cipher key being associated with a Universal Mobile Telecommunications System (UMTS) security context and being generated from a 64-bit cipher key associated with a Global System for Mobile Communication (GSM) security context, wherein the 128-bit cipher key is usable in the encryption algorithm in accordance with a GSM communication mode.