Method and apparatus for establishing a security association

Abstract

A method for establishing a security association between a client and a service node for the purpose of pushing information from the service node to the client, where the client and a key server share a base secret. The method comprises sending a request for generation and provision of a service key from the service node to a key server, the request identifying the client and the service node, generating a service key at the key server using the identities of the client and the service node, the base secret, and additional information, and sending the service key to the service node together with said additional information, forwarding said additional information from the service node to the client, and at the client, generating said service key using the received additional information and the base key. A similar approach may be used to provide p2p key management.

1 .- 28 . (canceled) 
     
     
         29 . A method of establishing a security association between a first node and a second node for pushing information from the first node to the second node, wherein the second node and a key generation function share a secret, the method comprising:
 sending, by the first node, a request for generation and provision of a service key from the first node to the key generation function, the request comprising an identity of the first node and an identity of the second node;   generating, by the key generation function, the service key using the identity of the first node, the secret, and additional information;   signing, by the key generation function, the additional information using a derivative of the secret;   sending, by the key generation function, the service key to the first node together with the additional information;   forwarding, by the first node, the additional information and the identity of the first node from the first node to the second node;   verifying, by the second node, the additional information; and   generating, by the second node, the service key using at least the additional information, the identity of the first node, and the secret.   
     
     
         30 . The method according to  claim 29 , wherein the first node is a service node and the second node is a client. 
     
     
         31 . The method according to  claim 30 , wherein the client is a client terminal of a 3G network employing a Generic Bootstrapping Architecture, and wherein the service node comprises a Network Application Function and the key generation function comprises a Bootstrapping Server Function. 
     
     
         32 . The method according  claim 31 , wherein the generating, by the key generation function, the service key further comprises:
 generating, by the key generation function, key material using the secret; and   generating, by the key generation function, the service key using the key material , the identity of the service node, and the additional information.   
     
     
         33 . The method according to  claim 31 , wherein the generating, by the client, the service key, further comprises:
 generating, by the client, key material using the secret; and   generating, by the client, the service key using the key material and the additional information.   
     
     
         34 . The method according to  claim 33 , wherein the secret is stored in an IP Multimedia Services Identity Module (ISIM) or Universal Subscriber Identity Module (USIM) of the client, and the generating, by the client, the key material is performed by the ISIM or the USIM. 
     
     
         35 . The method according to  claim 30 , wherein the generating, by the key generation function, the service key further comprises generating, by the key generation function, the service key utilizing values other than values sent to the client by the service node. 
     
     
         36 . The method according to  claim 35 , wherein at least some of the values other than values sent to the client by the service node are values obtained by the client from the key generation function. 
     
     
         37 . The method according to  claim 29 , wherein the additional information comprises at least one or more of:
 a transaction identifier; and   a network authentication value.   
     
     
         38 . The method according to  claim 29 , wherein the additional information comprises a transaction identifier in a format of a Network Access Identifier (NAI), wherein the transaction identifier further comprises an encoded random value generated by the key generation function, the encoded random value being used, by the second node, to generate the service key. 
     
     
         39 . The method according to  claim 30 , wherein the additional information comprises a transaction identifier in a format of a Network Access Identifier (NAI), wherein the transaction identifier further comprises a pointer to a random value generated by and stored at the key generation function, the random value being used, by the client, to generate the service key, wherein the method further comprises:
 sending, by the client, the pointer from the client to the key generation function; and   returning, by the key generation function, the random value to the client the random value being used, by the client, to generate the service key.   
     
     
         40 . The method according to  claim 30 , wherein the key generation function sends to the service node a network authentication value and the service node forwards the network authentication value to the client, together with the additional information, wherein the client uses the secret and the network authentication value to authenticate information received from the key generation function. 
     
     
         41 . The method according to  claim 30 , comprising:
 sending, by the client, a request from the client to the key generation function for an authentication value after the client receives the additional information from the service node;   receiving, by the client, the authentication value; and   authorizing, by the client, the request received from the service node on the basis of the authentication value.   
     
     
         42 . The method according to  claim 30 , wherein the additional information is forwarded from the service node to the client in a message that further comprises service data, wherein the service data is encrypted or integrity protected with the service key, and wherein the client can decrypt the encrypted data once the client has generated the service key. 
     
     
         43 . The method according to  claim 29 , wherein the key generation function generates the service key further using the identity of the second node. 
     
     
         44 . The method according to  claim 29 , wherein the service key is a Diffie-Hellman key for the second node, and the method further comprises:
 providing, to the first node, a Diffie-Hellman key for the first node; and   sending the Diffie-Hellman key for the first node to the second node, the security association being established on a basis of the Diffie-Hellman key for the first node and the Diffie-Hellman key for the second node.   
     
     
         45 . The method according to  claim 29 , wherein the first node is a first client and the second node is a second client. 
     
     
         46 . The method according to  claim 45 , wherein the key generation function is implemented on a key server having a trust relationship with the second client and the request for generation and provision of the service key is sent to the key server via a second key server having a trust relationship with the first client. 
     
     
         47 . The method according to  claim 46 , further comprising:
 sending, by the first node, from the first node to the second node, the service key obtained by the first node, and deriving, at the first node and the second node, a session key using the service key obtained by the first node and the service key generated at the second node.   
     
     
         48 . A service node arranged to deliver a push service to a client terminal via a secure communication link, the service node comprising:
 a transmitter arranged to send a request for generating and provisioning of a service key to a key generation function, the request comprising an identity of the client terminal and an identity of the service node;   a receiver arranged to receive, from the key generation function, the service key together with additional information, the additional information having been signed using a derivative of a secret shared by the client terminal and the key generation function;   a forwarder arranged to forward the additional information to the client terminal; and   a sender arranged to encrypt or protect integrity of service information using the service key and to send the encrypted or protected information to the client terminal.   
     
     
         49 . A client terminal arranged to receive a pushed service delivered by a service node, the client terminal comprising:
 a storage medium for storing a secret that is shared with a key generation function;   a receiver arranged to receive, from the service node, key generation information, the key generation information having been signed using a derivative of the secret; and   a verifier arranged to verify the key generation information using the derivative of the secret; and   a generator arranged to generate a service key using the key generation information.   
     
     
         50 . The client terminal according to  claim 49 , wherein the verifier is further arranged to use the service key to decrypt or verify integrity of communications with the service node. 
     
     
         51 . The client terminal according to  claim 49 , wherein
 the receiver is further arranged to receive from the service node a message authentication code; and   the generator is further arranged to generate at least one authentication key from at least a part of the key generation information, and to use the at least one authentication key to verify the message authentication code.   
     
     
         52 . The client terminal according to  claim 51 , wherein
 the generator is further arranged to generate the at least one authentication key by sending the key generation information to an IP Multimedia Services Identity Module (ISIM) or Universal Subscriber Identity Module (USIM).   
     
     
         53 . A key server implementing a key generation function arranged to establish a security association between a client terminal and a service node for pushing information from the service node to the client terminal, the key server comprising:
 a storage medium for storing a secret that is shared with the client terminal;   a receiver to receive a request for generating and provisioning of a service key from the service node, the request comprising an identity of the client terminal and an identity of the service node; and   a generator arranged to generate the service key using the identity of the service node, the secret, and key generation information, to sign the key generation information using a derivative of the secret, and to send the service key to the service node along with the key generation information.   
     
     
         54 . A method of establishing a security association between a first client and a second client for pushing information from the first client to the second client, wherein the first client has a trust relationship with a first key server and the second client has a trust relationship with a second key server, and wherein the first client shares a first secret with the first key server and the second client shares a second secret with the second key server, the method comprising:
 sending, by the first key server, a request for generation and provision of a service key from the first client to the second key server via the first key server, the request comprising an identity of the first client and an identity of the second client;   generating, by the second key server, the service key using the identity of the first client, the secret, and key generation information;   signing, by the second key server, the key generation information, using a derivative of the secret;   sending, by the second key server, the service key to the first client together with the key generation information;   forwarding, by the first client, the key generation information from the first client to the second client;   verifying, by the second client, the key generation information using the derivative of the secret; and   generating, by the second client, using the service key using the key generation information and the secret.   
     
     
         55 . A method in a client terminal for receiving a pushed service delivered by a service node, the method comprising:
 storing a secret that is shared with a key generation function;   receiving, from the service node, key generation information, the key generation information having been signed using a derivative of the secret;   verifying the key generation information using the derivative of the secret; and   generating a service key using the key generation information and the secret.   
     
     
         56 . The method according to  claim 55 , further comprising:
 using the service key to decrypt or verify integrity of communications with the service node.   
     
     
         57 . The method according to  claim 56 , further comprising:
 receiving, from the service node, a message authentication code;   generating at least one authentication key from at least a part of the key generation information; and   using the at least one authentication key to verify the message authentication code.   
     
     
         58 . The method according to  claim 57 , wherein the generating the at least one authentication key is performed by sending the key generation information to an IP Multimedia Services Identity Module (ISIM) or Universal Subscriber Identity Module (USIM).