Mtc key management for key derivation at both ue and network

Abstract

There is provided a new IWF SMC procedure for establishing security association between an MTC UE ( 10 ) and an MTC-IWF ( 20 ). The MTC-IWF ( 20 ) sends to the UE ( 10 ) at least an algorithm identifier which instructs the UE ( 10 ) to select one of algorithms for deriving a root key (K_iwf). The UE ( 10 ) derives the root key (K_iwf) in accordance with the selected algorithm, and derives at least a subkey for checking the integrity of messages transferred between the UE ( 10 ) and the MTC-IWF ( 20 ) by using the derived root key (K_iwf). The UE ( 10 ) protects uplink messages transmitted to the MTC-IWF ( 20 ) with the derived subkey. The MTC-IWF ( 20 ) protects downlink messages transmitted to the UE ( 10 ) with the same subkey derived at a core network.

1 . A communication system comprising:
 an MTC-IWF (MTC (Machine-Type-Communication) Inter-Working Function); and   a UE (User Equipment),   wherein the MTC-IWF stores a master key, derives subkeys for confidentiality and integrity protection, and informs the UE about an algorithm for key derivation,   wherein the UE derives, by using the algorithm, the master key and the subkeys such that the UE shares the same master key and the same subkeys with the MTC-IWF,   wherein security association is established between the UE and the MTC-IWF by using the shared master key and subkeys.   
     
     
         2 . The communication system according to  claim 1 , further comprising:
 an HSS (Home Subscriber Server) that derives the master key and sends the master key to the MTC-IWF.   
     
     
         3 . The communication system according to  claim 2 , wherein the MTC-IWF stores the master key received from the HSS. 
     
     
         4 . The communication system according to  claim 1 , wherein the MTC-IWF derives the subkeys from the master key. 
     
     
         5 . The communication system according to  claim 1 , wherein the informing of the algorithm rides on NAS SMC (Non-Access Stratum Security Mode Command). 
     
     
         6 . The communication system according to  claim 5 , further comprising:
 an MME (Mobility Management Entity) that carries a NAS SMC message to the UE,   wherein the NAS SMC message includes an IWF SMC message for informing the UE about the algorithm.   
     
     
         7 . An MTC-IWF configured to store a master key, derive subkeys for confidentiality and integrity protection, and inform a UE about an algorithm for key derivation to cause the UE to derive the master key and the subkeys such that the UE shares the same master key and the same subkeys with the MTC-IWF,
 wherein security association is established between the UE and the MTC-IWF by using the shared master key and subkeys.   
     
     
         8 . The MTC-IWF according to  claim 7 , further configured to receive and store the master key from an HSS. 
     
     
         9 . The MTC-IWF according to  claim 7 , further configured to derive the subkeys from the master key. 
     
     
         10 . The MTC-IWF according to  claim 7 , further configured to send an IWF SMC message for informing the UE about the algorithm to an MME that carries a NAS SMC message to the UE. 
     
     
         11 . A UE configured to derive, by using an algorithm for key derivation informed from an MTC-IWF, a master key and subkeys for confidentiality and integrity protection such that the UE shares the master key and the subkeys with the MTC-IWF,
 wherein security association is established between the UE and the MTC-IWF by using the shared master key and subkeys.   
     
     
         12 . The UE according to  claim 11 , further configured to derive the subkeys from the master key. 
     
     
         13 . The UE according to  claim 11 , further configured to receive from an MME a NAS SMC message that includes an IWF SMC message for informing about the algorithm. 
     
     
         14 - 15 . (canceled) 
     
     
         16 . A method of securing MTC communication, the method comprising:
 storing, by an MTC-IWF, a master key;   deriving, by the MTC-IWF, subkeys for confidentiality and integrity protection;   informing, by the MTC-IWF, a UE about an algorithm for key derivation; and   deriving, by the UE using the algorithm, the master key and the subkeys such that the UE shares the same master key and the same subkeys with the MTC-IWF,   wherein security association is established between the UE and the MTC-IWF by using the shared master key and subkeys.   
     
     
         17 . The method according to  claim 16 , further comprising:
 deriving, by an HSS, the master key; and   sending, by the HSS, the master key to the MTC-IWF.   
     
     
         18 . The method according to  claim 17 , further comprising:
 storing, by the MTC-IWF, the master key received from the HSS.   
     
     
         19 . The method according to  claim 16 , wherein the MTC-IWF derives the subkeys from the master key. 
     
     
         20 . The method according to  claim 16 , wherein the informing of the algorithm rides on NAS SMC. 
     
     
         21 . The method according to  claim 20 , further comprising:
 carrying, by an MME, a NAS SMC message to the UE,   wherein the NAS SMC message includes an IWF SMC message for informing the UE about the algorithm.