Methods and Apparatuses Generating a Radio Base Station Key in a Cellular Radio System

Abstract

In a method and a system for providing secure communication in a cellular radio system radio base station key is generated by determining a set of data bits known to both the UE and the radio base station, and creating the radio base station key in response to the determined set of data.

What is claimed is: 
     
         1 . A method of creating a derived radio base station key in a source radio base station of a cellular radio system in a connection with a User Equipment (UE) being connectable to the cellular radio system, said method comprising:
 creating the radio base station key based on a determined set of data and an existing cryptographic key used for communication between the UE and the source radio base station;   wherein the determined set of data is a physical cell identity specific to a particular target cell, known to both the UE and the source radio base station.   
     
     
         2 . The method according to  claim 1 , further comprising using additional input parameters as input data when creating the derived radio base station key. 
     
     
         3 . The method according to  claim 1 , further comprising creating the derived radio base station key using a Pseudo Random Function. 
     
     
         4 . A node for use in a cellular radio system, the node being adapted to create a derived radio base station key, and wherein the node is configured to:
 determine a public physical cell identity specific to a particular target cell known to both a User Equipment (UE) communicating with the cellular radio system via a secure communication associated with an existing cryptographic key and a radio base station of the cellular radio system; and   create the radio base station key based on the physical cell identity and the existing key.   
     
     
         5 . The node according to  claim 4 , wherein the node is configured to use additional input parameters as input data when creating the derived radio base station key. 
     
     
         6 . The node according to  claim 4 , wherein the node is configured to create the derived radio base station key using a Pseudo Random Function. 
     
     
         7 . A method of creating a Terminal Identity Token for identifying a User Equipment (UE) connected to a radio base station in a radio system, wherein the UE communicates with a radio base station via a secure communication associated with an existing cryptographic key, said method comprising:
 creating the Terminal Identity Token based on a physical cell identity of a target cell known to both the UE and the radio base station, the terminal identity and the existing key.   
     
     
         8 . The method according to  claim 7 , further comprising using additional input parameters as input data when creating the Terminal Identity Token. 
     
     
         9 . The method according to any  claim 7 , further comprising creating the Terminal Identity Token using a Pseudo Random Function. 
     
     
         10 . The method according to  claim 7 , wherein the method is performed in the UE. 
     
     
         11 . The method according to  claim 10 , further comprising transmitting the Terminal Identity Token to one of the radio base stations of the radio system as an identity of the UE. 
     
     
         12 . The method according to  claim 11 , further comprising generating the Terminal Identity Token as a Pseudo Random Function using the terminal identity and the existing key and additional parameters as input. 
     
     
         13 . The method according to  claim 7 , wherein the method is performed in a radio base station acting as a source radio base station. 
     
     
         14 . The method according to  claim 13 , further comprising distributing the Terminal Identity Token to a number of target radio base stations of the radio system. 
     
     
         15 . A method in a radio base station acting as a target base station for identifying a User Equipment (UE) wherein the UE communicates with a source radio base station via a secure communication associated with an existing cryptographic key, said method comprising:
 receiving a Terminal Identity Token from a source base station, the Terminal Identity Token being generated by the source base station based on a physical cell identity of a target cell, the terminal identity and the existing key;   receiving a Terminal Identity Token from a UE, the Terminal Identity Token being generated by the UE based on a physical cell identity of a target cell, the terminal identity and the existing key; and   identifying the UE in the target radio base station based on the received Terminal Identity Token.   
     
     
         16 . The method according to  claim 15 , further comprising:
 receiving a first Terminal Identity Token from a source radio base station to which the UE is currently connected;   receiving a second Terminal Identity Token from the UE;   identifying the UE in the target radio base station by comparing the first and second Terminal Identity Tokens, wherein both the first and second Terminal Identity Tokens are created in response to the terminal identity and the existing key.   
     
     
         17 . The method according to  claim 16 , wherein the second Terminal Identity Token is generated as a Pseudo Random Function using the terminal identity and the existing key and also other parameters as input. 
     
     
         18 . The method according to  claim 16 , wherein the first Terminal Identity Token is generated as a Pseudo Random Function using the second Terminal identity Token and other parameters as input. 
     
     
         19 . A User Equipment (UE) adapted to identify itself, the UE being connectable to a radio base station in a radio system and adapted to communicate with a base station of the radio system via a secure communication associated with a unique existing encryption key, and wherein said UE is configured to:
 create the Terminal Identity Token based on a physical cell identity of a target cell known to both the UE and the radio base station, the terminal identity and the existing key; and   transmit the Terminal Identity Token to one of the radio base stations of the radio system as an identity of the UE.   
     
     
         20 . The UE according to  claim 19 , wherein the UE is configured to use additional input parameters as input data when creating the Terminal Identity Token. 
     
     
         21 . The UE according to  claim 19 , wherein the use is configured to create the Terminal Identity Token using a Pseudo Random Function.