Abstract:
According to a first aspect of the present invention there is provided a method of at least partly delegating processing of data in a machine-to-machine system to reduce computational load on a broker entity  11  while maintaining security of the data to be processed, the broker entity  11  serving as a link between a node  13  of a sensor network providing the data and an application node  12  requesting the data. In the method, at the broker entity  11 , following receipt of a request for processed data from the application node  12 , determining the node to provide the data to be processed, generating a data key for the data-providing node  13 , generating a data-processing algorithm for processing the data in dependence upon the request, sending the data key to the data-providing node  13 , and sending the data key and data-processing algorithm to a remote data-processing entity  15 . At the data-providing node  13 , encrypting the data using the data key and sending the encrypted data to the data-processing entity  15 . At the data-processing entity  15 , decrypting the data using the data key, processing the data using the data-processing algorithm, and sending the processed data to the application node  12.

Description:
TECHNICAL FIELD 
     The present invention relates to a method and apparatus for use in a Machine-to-Machine communication system. 
     BACKGROUND 
     The term M2M (Machine-to-Machine) generally refers to data communications between machines in the form of telemetry or telematics. M2M communication can take place over Ethernet, Public Switched Telephone networks (PSTN) or the Internet but in recent years an increasing proportion of M2M communication now takes place over public wireless data networks such as the General Packet Radio Service (GPRS). 
     In the M2M world most communication is message based and is therefore suitable for going through a proxy.  FIG. 1  of the accompanying drawings illustrates schematically a known M2M system comprised of a Broker  1 , one or several Applications  2 , and one or more Sensor Networks (SN)  3 . Each SN  3  comprises at least one data collecting device (not shown) and communicates with the Broker  1  via an SN Gateway  4 . The Broker  1  collects data from all SNs  3  and provides data services to the Applications  2 , performing data processing and aggregation services so that the Applications  2  can be provided with processed data from any of a number of SNs  3 . The Broker  1  also provides data access authorization and a data market place for individual sensor network providers. In such a system, the SN Gateway  4  of each individual SN  3  can be a very simple device, only authenticating and communicating with the Broker  1 . 
     With the rapid deployment of SNs and increased usage of M2M communication, the data processing workload of a Broker can be significant, especially when streaming data is sent from a SN. It is desirable to address this issue. 
     The article “Unified Management of Heterogeneous Sensor Networks in the Atlantis Framework” by Vesselin Arnaudov (Department of Computer Science, Brown University, Undergraduate Honors Theses, online) discloses a method of processing of data in a machine-to-machine system including a broker entity serving as a link between a node of a sensor network providing the data and an application node requesting the data. 
     SUMMARY 
     According to a first aspect of the present invention there is provided a method of at least partly delegating processing of data in a machine-to-machine system to reduce computational load on a broker entity while maintaining security of the data to be processed, the broker entity serving as a link between a node of a sensor network providing the data and an application node requesting the data. In the method, at the broker entity, following receipt of a request for processed data from the application node, the node to provide the data to be processed is determined, a data key for the data-providing node is generated, a data-processing algorithm for processing the data in dependence upon the request is generated, the data key is sent to the data-providing node, and the data key and data-processing algorithm are sent to a remote data-processing entity. At the data-providing node, the data is encrypted using the data key and sent to the data-processing entity. At the data-processing entity, the data is decrypted using the data key, processed using the data-processing algorithm and the processed data is sent to the application node. 
     Embodiments of the present invention provide for distribution of data processing to increase scalability of M2M systems whilst maintaining the privacy of the information provided by sensor network. 
     Embodiments of the present invention provide that the data-processing entity is authenticated by sending a message from the broker entity to the data-processing entity, for example via the application node, requesting the data-processing entity&#39;s public key certificate. The data-processing entity sends a message to the broker, for example via the application node, containing the data-processing entity&#39;s public key certificate and the broker entity confirms if the certificate is valid. 
     In a particular implementation, the step of sending the data key and data-processing algorithm to the data-processing entity comprises, at the broker entity, encrypting the data key and data-processing algorithm using a public key of the data-processing entity, sending the encrypted data key and data-processing algorithm to the data-processing entity. At the data-processing entity, the data key and data-processing algorithm are decrypted using the data-processing entities private key. 
     It may be that the data-processing algorithm is arranged so as to filter out at least some information from the data it is used to process and that only the processed data is sent to the application node, thereby hiding the unprocessed data from the application node. 
     The data key and data-processing algorithm may be sent to the data-processing entity via the application node. 
     The sending of data from the data-providing node to the data-processing entity may bypass the broker entity. The data-providing node may comprise a plurality of nodes. 
     The method may further comprise sending a further data-processing algorithm to the data-processing entity, and using this data-processing algorithm at the data-processing entity to process already-received data. At the data-processing entity, the data processed using the further data-processing algorithm may be sent to a further application node associated with the further data-processing algorithm. 
     In a particular implementation, the step of sending the data to the data-processing entity comprises, establishing a communication network session between the data-providing node and the data-processing entity, and sending the data using the communication network session. 
     Establishing the communication network session may comprise, at the broker entity, generating an access token and a session key and sending these to the data-providing node, the data-providing node using the access token and the session key to authenticate and register with the communication network, and once the data-providing node is registered with the communication network, the data-providing node sending a session initiation message to the data-processing entity. The session key may be a cryptographic function of the broker&#39;s public key and a session identifier, and the access token may comprise at least the identity of the broker and the session identifier signed with a private key of the broker. 
     Authenticating and registering the data-providing node with the communication network may comprise, sending a register message containing the access token to the communication network, the communication network using the identity of the broker contained within the access token to determine the public key of the broker, using the session identifier contained within the access token and the public key of the broker to calculate the session key, and using the session key as a shared secret to mutually authenticate the communication network and the data-providing node. 
     The communication network may be an IP Multimedia Subsystem. 
     The data-processing entity may be provided in an application environment associated with the application node. 
     According to a second aspect of the present invention there is provided a broker entity. The broker entity comprising a receiver for receiving the request for processed data from the application node, a data reasoner for determining the node to provide the data to be processed and generating the data-processing algorithm to process the data in dependence upon the request, a key generator for generating the data key for the data-providing node, a transmitter for sending the data key to the data-providing node, and a transmitter for sending the data key and data-processing algorithm to the remote data-processing entity. 
     The broker entity may further comprise a transmitter for sending a message to the data-processing entity requesting the data-processing entity&#39;s public key certificate, a receiver for receiving a message containing the data-processing entity&#39;s public key certificate, and a processor for confirming if the certificate is valid and authenticating the data-processing entity. 
     According to a third aspect of the present invention there is provided a data-providing node. The data-providing node comprising a receiver for receiving the data key, an encryptor for encrypting the requested data using the data key, and a transmitter for sending the encrypted data to the data-processing entity. 
     The data-providing node may further comprise means for establishing a communication network session with the data-processing entity and a transmitter for sending the data using the communication network session. 
     According to a fourth aspect of the present invention there is provided a data-processing entity. The data-processing entity comprising a receiver for receiving the data key and the data-processing algorithm from the broker entity, a receiver for receiving the encrypted data from the data-providing node, a decryptor for decrypting the data using the data key, a processor for processing the data using the data-processing algorithm, and a transmitter for sending the processed data to the application node. 
     The data-processing entity may further comprise a receiver for receiving a message requesting its public key certificate and a transmitter for sending a message containing the public key certificate. 
     According to a fifth aspect of the present invention there is provided a method of establishing a communication network session between first and second client terminals using a subscription of an interlinking node. In the method, at the interlinking node, generating an access token and a session key and sending these to the first client terminal, the first client terminal using the access token and the session key for authenticating and registering with the communication network and, once the first client terminal is registered with the communication network, sending a session initiation message to the second client terminal over the communication network to initiate establishment of the session. 
     The session key may be a cryptographic function of the interlinking node&#39;s public key and a session identifier, and the access token may comprise at least the identity of the interlinking node and the session identifier signed with a private key of the interlinking node. 
     In a particular implementation, the step of authenticating and registering the first client terminal with the communication network comprises sending a register message containing the access token to the communication network, the communication network using the identity of the interlinking node contained within the access token to determine the public key of the interlinking node, using the session identifier contained within the access token and the public key of the interlinking node to calculate the session key, and using the session key as a shared secret to mutually authenticate the communication network and the first client terminal. 
     The communication network may be an IP Multimedia Subsystem. 
     According to a further aspect of the present invention there is provided a method of providing data from a sensor network to an application in an application environment, comprising arranging for a data-processing algorithm to be provided to a trusted data processor in the application environment, and for the data to be provided from the sensor network to the trusted data processor for processing by the trusted data processor using the data-processing algorithm, with the processed data being forwarded to the application. It may be that only the processed data is forwarded to the application. The data may be provided securely from the sensor network to the trusted data processor. 
     The data provided from the sensor network to the trusted data processor may bypass a broker entity arranged between the sensor network and the application for providing data services to the application. Further data-processing algorithms may be provided to the trusted data processor for processing existing data previously provided from the sensor network to the trusted data processor, this processed data being forwarding to the same or a different application. 
     An embodiment of the present invention provides at least one of the following advantages:
         Distributes the workload to increase scalability of the M2M system   Protects the privacy of the information provided by the SNs   That the Broker may control the traffic from the SNs to the Application   That the SN Gateway may use the IMS network without an ISIM or an IMS subscription.       

    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1 , discussed hereinbefore, illustrates schematically a known M2M System; 
         FIG. 2  illustrates schematically a M2M System according to an embodiment of the present invention; 
         FIG. 3  illustrates schematically a Trusted Data Processor according to an embodiment of the present invention; 
         FIG. 4  illustrates an example signalling flow of a secure task delegation process according to an embodiment of the present invention; and 
         FIG. 5  illustrates an example signalling flow of an IMS Registration and session establishment for a secure task delegation process according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     As mentioned above, with the rapid deployment of SNs and increased usage of M2M communication, the data processing workload of a Broker can be significant, especially when streaming data is sent from a SN. It is therefore desirable that the Broker can delegate some of its data processing tasks to Applications in order to maintain scalability of the system. Delegating tasks to Applications in order to reduce the workload on the Brokers requires that the SNs send data directly to those Applications. In addition, when the data being sent from a SN to an Application is in a streamed format and no further processing is required, it would be better if the gateway of the SN could transmit the data directly to the recipient Application. 
     When the data processing is done at the Broker level, the Broker may filter out sensitive information so that the Applications only receive that information which they are allowed to receive. By sending information directly from SNs to the Applications, the Applications may obtain additional information that they are not authorised to. Therefore, there is a need for a system that can delegate tasks whilst maintaining the desired level of security. 
       FIG. 2  illustrates schematically an M2M system according to an embodiment of the present invention and comprises a Broker  11 , an Application Environment  10 , and one or more Sensor Networks (SN)  13 . An Application Environment  10  is associated with one or several Applications  12  and is provided with at least one Trusted Data Processor (TDP)  15  to which a Broker  11  may delegate data processing tasks. 
     If a Broker  11  has delegated a data processing task to a TDP  15 , then the SNs  13  can provide the data directly to that TDP  15 , which processes the data and provides it to the Application  12 . The data processing performed by the TDP  15  ensures that the Application  12  only receives information that it is authorised to receive. 
     To ensure that the TDP  15  can be trusted with the unprocessed data, the Broker  11  confirms that a trusted Certificate Authority (CA) has issued the TDP  15  with a public key certificate. The CA ensures that the TDP  15  conforms with its the compliance rules such that a TDP  15  with a valid public key certificate is trusted to receive the same level of sensitive information as the Broker  11 . If a TDP  15  has been compromised then the CA can revoke its certificate. 
     The Broker  11  comprises Data Reasoner  16 , a Key Generator  17 , a Transmitter  18  and a Receiver  19 . The Data Reasoner  16  analyses a request received from an Application  12  and decides from which SNs  13  the data is going to be collected and how the data is going to be processed. The Key Generator  17  generates keys to be used by the source SNs  13  to encrypt the data. The TDP  15  in the Application Environment  10  decrypts the data from the SNs  13 , processes the data and provides the Application  12  with the processed results. The Application Environment  10  belongs to an M2M service provider and the M2M service provider can use the same TDP  15  for all its Applications. 
       FIG. 3  schematically illustrates the TDP  15  of  FIG. 2  in more detail. The TDP  15  comprises a Data Decryptor  20 , a Data Processing Unit  21 , a Key and Algorithm Decryptor  22 , a Transmitter  24  and a Receiver  23 . The algorithms and keys sent to the TDP  15 , from Broker  11  via the Application  12 , are encrypted so that the Applications cannot use them directly. The Key and Algorithm Decryptor  22  decrypts the algorithms and the keys. The Data Decryptor  20  then uses the keys K 1 , K 2  provided by the Broker  11  to decrypt the data from SNs  13 . The Data Processing Unit  21  uses the processing algorithm F to process the data and provides the results to the Application  12 . The TDP  15  may also comprise a memory unit that could be used to cache the algorithm for re-use on further data, varying only any control parameters as required, or to cache the received data for processing using further algorithms. 
     It is assumed that the Broker  11  has security associations with the SNs  13  such that, when sensitive information (e.g. keys) is sent from the Broker  11  to SNs  13 , the information is protected from eavesdropping and modifications. By way of example, these security associations could be established using the Internet Key Exchange (IKE) protocol as in the IPsec protocol suite. 
     The above concept will now be described in more detail with reference to  FIG. 4 , which shows a simplified signalling flow diagram in a situation where an Application  12  makes a request for service requiring data from two different SNs  13 . The steps performed are as follows:
     S 1 . The Application  12  sends a request to the Broker  11  asking for a service.   S 2 . The Broker  11  sends a request to the TDP  15 , via the Application  12 , to present its certificate and checks whether the certificate has expired or has been revoked. If the certificate is valid and the Broker  11  successfully authenticates the TDP  15  using the public key contained in the certificate, it continues with step S 3 . Otherwise the Broker  11  rejects the Application&#39;s request.   S 3 . The Data Reasoner  16  within the Broker  11  analyses the request from the Application  12  and decides from which SNs  13  the data is going to be collected. For each source SN  13 , it instructs the Key Generator  17  to generate a data key K and sends it to the SN  13 .   S 4 . The Data Reasoner  16  also produces a data processing algorithm F that identifies the source SNs  13  and provides the algorithm F that the TDP  15  will use to process the data from those SNs  13 .   S 5 . The Broker  11  encrypts the data keys K 1 , K 2  (generated by the Key Generator  17  at step S 3 ) and the algorithm F (produced by the Data Reasoner  16  at step S 4 ) with the TDP&#39;s public key K TDP  and the result (i.e. (K 1 , K 2 , F) K TDP ) is sent to the Application  12 .   S 6 . The Application  12  forwards the encrypted data keys K 1 , K 2  and data processing algorithm F (i.e. (K 1 , K 2 , F) K TDP ) received at step S 5  to the TDP  15 .   S 7 . The SNs  13  collect data P. For each SN  13 , when the data P is ready, the SN  13  encrypts P with the data key K 1  or K 2  received from the Broker  11  to produce encrypted data C (i.e. C=(P)K). The encrypted data C is sent to the TDP  15  in a communication session. The session can be established according to the procedures described below.   S 8 . The Key and Algorithm Decryptor  22  of the TDP  15  decrypts the data keys K 1 , K 2  and the data processing algorithm F by using its private key. It sends the data keys K 1 , K 2  and the algorithm F to the Data Decryptor  20  and the Data Processing Unit  21  respectively.   S 9 . The Data Decryptor  20  within the TDP  15  decrypts each input C by using the corresponding data key K 1  or K 2  and recovers the data P. The Data Processing Unit  21  within the TDP  15  processes the plaintext data (P 1  and P 2  as shown in  FIG. 3 ) according to the algorithm F, generating a result (R).   S 10 . The TDP  15  outputs the result R to the Application  12 .   

     The data processing acts so as to “filter out” sensitive information, either by removing it or by performing some irreversible modification to it such that the details of this information can no longer be ascertained, with only the processed result being sent to the Application  12 . The unencrypted plaintext data (P 1 , P 2 ) is never exposed outside of the TDP  15 . Given that only the TDP  15  knows its private key, the Application  12  cannot decrypt the data keys provided by the Broker  11  and therefore cannot decrypt the unprocessed data such that the Applications only receive that information which they are allowed to receive 
     As part of the process of delegating data processing tasks from the Broker  11  to the TDP  15 , the Broker  11  redirects the data traffic from the SNs  13  directly to the TDP  15 , bypassing the Broker  11 . This may require that a communication session be established directly between the SNs  13  and the TDP  15  in the Application Environment  10 . This communication can be done in several ways, such as using an Internet Protocol (IP) or IP Multimedia Subsystem (IMS) connection. The following discussion refers to the use of an IP Multimedia Subsystem (IMS) as an example communication network, but it can also be applied to other networks. 
     IP Multimedia Subsystem (IMS) is the technology defined by the Third Generation Partnership Project (3G) to provide IP Multimedia services over mobile communication networks. IMS provides a dynamic combination of voice, video, messaging, data, etc. within the same session. The IMS makes use of the Session Initiation Protocol (SIP) to set up and control calls or sessions between user terminals (or user terminals and application servers). SIP makes it possible for a calling party to establish a packet switched session to a called party (using so-called SIP User Agents, UAs, installed in the user terminals) even though the calling party does not know the current IP address of the called party prior to initiating the call. The Session Description Protocol (SDP), carried by SIP signalling, is used to describe and negotiate the media components of the session. Whilst SIP was created as a user-to-user protocol, IMS allows operators and service providers to control user access to services and to charge users accordingly. 
     If the communication between the SNs  13  and the TDP  15  was to take place over an IMS network this would require that either the SNs have an IMS subscription, or the Broker and the IMS provider are the same entity or that the SNs are able to make use of a third party&#39;s IMS subscription. 
     If the SNs  13  themselves do not have direct access or a subscription to an IMS network, and given that the Broker  11  redirects the data traffic from the SNs  13  directly to the TDP  15 , it is reasonable that the Broker  11  is charged for the traffic. Therefore, a process for accessing a third party network is further presented here. 
     In order to establish an IMS session, the Broker  11  also provides the gateway  14  of each SN  13  with an indirect Access Token and a session key K SESSION  when sending the request for data. In one embodiment, this session key can be computed as a cryptographic one-way function ƒ( ) of the session identifier session_ID and the public key K M2Mbroker  of the Broker  11 , i.e. K=ƒ(session_ID, K M2Mbroker ). In one embodiment, the Access Token consists of a signed set of critical information. For example, the token can include the SIP URI of the receiver, conditions to be met, the session identifier, the identity of the Broker  11  and the identity of the IMS Provider (IMSP), all signed using the private key SK M2Mbroker  of the Broker  11 , i.e. Access Token=(SIP URI of receiver, conditions, session_ID, Broker, IMSP) sign  SK M2Mbroker . 
       FIG. 5  shows a simplified signalling flow example in a situation where an Application  12  makes a request for service requiring data from an SN  13  wherein, the SN  13  requires the establishment of an IMS Session using the Broker&#39;s  11  IMS subscription to communicate directly with the TDP  15  in the Application Environment  10 . The steps performed are as follows:
     T 1 . As with step S 1  previously described with reference to  FIG. 4 , the Application  12  in the Application Environment  10  sends a request to the Broker  11  asking for a service.   T 2 . As with step S 2  previously described with reference to  FIG. 4 , the Broker  11  sends a request to the TDP  15 , via the Application  12 , to present its certificate and checks whether the certificate has expired or has been revoked. If the certificate is valid and the Broker  11  successfully authenticates the TDP  15  using the public key contained in the certificate, it continues with step T 3 . Otherwise the Broker  11  rejects the Application&#39;s request.   T 3 . The Broker  11  generates a data key K, equivalent to that generated in step S 3  previously described with reference to  FIG. 4 , for encrypting and decrypting the data. In addition, the Broker  11  also generates an Access Token and a session key K SESSION . The Broker  11  sends the data key K, the Access Token and the session key K SESSION  to the SN Gateway  14 .   T 4 . As with steps S 4  to S 6  previously described with reference to  FIG. 4 , the Broker  11  also produces a data processing algorithm F, encrypts the data key K (generated at step T 2 ) and the algorithm F with the public key K TDP  of the TDP  15  and the result is sent to the TDP  15  in the Application Environment  10 , via the Application  12 .   T 5 . The SN Gateway  14  then sends a REGISTER message including the Access Token to the P-CSCF (not shown) in the Visited IMS  31 .   T 6 . The P-CSCF identifies an I-CSCF (not shown) in the Home IMS  30  and forwards the REGISTER message. The I-CSCF in turn determines the S-CSCF (not shown) following reference to the HSS (not shown) and forwards the REGISTER message.   T 7 . The SN  13  is currently not authenticated, so the registration request is rejected and a 401 Unauthorised message is returned to the SN  13  with a challenge to authenticate the user.   T 8 . The SN  13  and IMS  30  are then mutually authenticated according to standard IMS AKA procedures, using the session key K SESSION .   T 9 . Once the SN  13  is registered with the IMS  30  it sends an INVITE message to the SIP URI of the recipient TDP  15 .   T 10 . An IMS Session is then established between the SN  13  and the TDP  15  in the Application Environment  10 . Steps S 7  to S 10  previously described with reference to  FIG. 4  can then take place directly between SN  13  and the TDP  15 .   

     In order to implement the process described above, the CSCFs need to understand that the Access Token should be transported to the HSS, and the HSS is required to understand the token, maintain a list of Brokers and their public keys and shared symmetric keys, and to be able to check the conditions. Examples of the conditions could be the time of day, session duration session or results of other sensor measurements etc. This could for instance allow for independent control of when sessions should be initiated, for example, ensuring that a session does not have a privacy impact when related to a video stream from a home. The S-CSCF also needs to be able to enforce these conditions, preventing session initiation if the conditions are not met. The S-CSCF together with the HSS checks the conditions, the signature of the token and computes the key K SESSION  using the session_ID and K M2MBroker . K SESSION  is then used as a shared secret between the SN and the IMS to perform mutual authentication using AKA without the need for an ISIM. 
     Once the SN Gateway  14  is authenticated and given a temporary SIP URI, it can initiate the allowed session(s) corresponding to the SIP URI of the receiver and the conditions. 
     As described above, the data sent from the SNs  13  to the TDP  15  is securely bootstrapped using the data keys K sent by the Broker  11  to both the TDP  15  and the SNs  13 . The explicit method used for this is out of scope of the present invention but, for example, could be based on TLS using pre-shared keys. 
     When the SN  13  has a subscription to establish a communication channel with the TDP  15  or does not need subscription, the Broker  11  needs only to send the data key K to the SN  13  and the TDP  15 . If a subscription is needed for the SN  13  to establish a communication channel and the SN  13  does not have one, the Broker  11  needs to send the Access Token and the session key K session  along with the data key K to the SN  13 . 
     The above-described embodiments provide for the delegation of data processing to reduce computational load on a Broker while maintaining the security of the data, as it may contain private data that should not be accessible by certain applications. For example, GPS data can provide location information to within a few meters. If an application only requires information regarding the current city of location for its service, it is not appropriate to expose the detailed GPS data to the application as this may violate privacy constraints. In another example, an insurance company may require an individual&#39;s health index calculated using various parameters such as the individuals ECG measurements, blood pressure etc. Providing the detailed data of such parameters could also violate some privacy policy. 
     It will be appreciated by the person of skill in the art that various modifications may be made to the above-described embodiments without departing from the scope of the present invention.