Abstract:
Disclosed is a method for secure transmission of small data of a machine type communication (MTC) device group, comprising a process wherein an MTC device and an MTC-Interworking Function (MTC-IWF) generate a shared key KIWF on the basis of a GBA procedure, the MTC device and a bootstrapping server (BSF) performing AKA authentication: a home subscriber server (HSS) determines whether the MTC device belongs to the MTC device group and whether said device has small data transmission and reception capabilities; if said device belongs to said group and has said capabilities, an AKA authentication vector generated on the basis of the MTC device group key is sent to said BSF; the BSF carries out AKA authentication with the MTC device on the basis of the received AKA authentication vector. Also disclosed is a system for secure transmission of small data of an MTC device group.

Description:
TECHNICAL FIELD 
       [0001]    The disclosure relates to a Generic Bootstrapping Architecture (GBA) key agreement technology, and in particular to a secure Small Data Transmission (SDT) method and system for a Machine Type Communication (MTC) device group. 
       BACKGROUND 
       [0002]    MTC refers to a generic term of a series of technologies and combinations thereof for implementing data communication and exchange between a machine and a machine and between a machine and a man by virtue of a wireless communication technology. MTC has two meanings: the first is a machine, which is called an intelligent device in the field of intelligence; and the second is a connection between a machine and a machine, the machines being connected through a network. MTC is widely applied to, for example, intelligent measurement and remote monitoring, and makes the life of people more intelligent. Compared with conventional interpersonal communication, MTC has the advantages of numerous MTC devices, wide application range and broad market prospect. 
         [0003]    In an existing MTC system, an MTC device communicates with a service server such as an MTC server through a 3rd Generation Partnership Project (3GPP) network and an MTC Interworking Function (MTC-IWF). 
         [0004]    A GBA defines a generic key agreement mechanism between a terminal and a server. 
         [0005]    After introduction of MTC devices, there are numerous MTC devices in a mobile communication system, so that it is necessary to perform management optimization on the MTC devices in groups to reduce a network load and save network resources. Moreover, these MTC devices may frequently send small data, thereby reducing efficiency of the mobile communication system. In order to efficiently utilize the network resources, it is necessary to enhance and optimize the mobile communication system according to SDT to improve SDT efficiency of the mobile communication system. Transmitting small data between an MTC device and each of an MTC-IWF and a service server through signalling is a very effective manner, may avoid allocation of user plane resources, and may also reduce utilization of radio resources. In addition, during SDT for the condition of MTC device groups, it is necessary to perform security control and management on MTC devices in groups. 
         [0006]    At present, an SDT protocol is introduced into a method for transmitting small data between an MTC device and each of an IWF and a service server through signalling, and is deployed in the MTC device and the MTC-IWF. Any piece of data is required to pass through the MTC-IWF for exchange between the MTC device and the service server. In the method, for ensuring security of data transmission between the MTC device and the MTC-IWF, it is necessary to create a shared key between the MTC device and the MTC-IWF. An existing solution is to create a key configured to protect secure SDT in the MTC-IWF through an Authentication and Key Agreement (AKA) process in an attachment process. In such a manner, in the same attachment process, the MTC device may perform secure SDT for many times by adopting the same small data transmission protection key. Using the same SDT protection key for multiple SDT processes increases a risk of attack to the SDT protection key. In addition, during a practical Machine-to-Machine (M2M) application, an MTC device may be required to initiate SDT for different destination servers in an attachment process, and for ensuring security, SDT for these different destination servers is required to be protected by different keys. Therefore, it is necessary to create a shared key configured to protect secure SDT between the MTC device and an MTC-IWF for each SDT process during SDT of the MTC device. For the condition of an MTC device group, it is necessary to create a shared key between a group of MTC devices and the MTC-IWF during each SDT of the MTC device group. How to create a shared key configured to protect secure SDT between a group of MTC devices and an MTC-IWF for each SDT is a technical problem urgent to be solved. 
       SUMMARY 
       [0007]    In order to solve the existing technical problem, the embodiment of the disclosure provides an SDT method and system for an MTC device group. 
         [0008]    The embodiment of the disclosure provides an SDT method for an MTC device group, which may include a process that an MTC device and an MTC-IWF generate a Ishared key K IWF  on the basis of a GBA key agreement process in which AKA authentication between the MTC device and a Bootstrapping Server Function (BSF) includes: 
         [0009]    a Home Subscriber Server (HSS) determines whether the MTC device belongs to the MTC device group and has a small data sending and receiving capability or not, and if YES, sends an AKA authentication vector generated on the basis of an MTC device group key to the BSF; and 
         [0010]    the BSF performs AKA authentication with the MTC device according to the received AKA authentication vector. 
         [0011]    In an embodiment, the method may further include: after the AKA authentication between the BSF and the MTC device succeeds, 
         [0012]    the MTC device and the BSF generate a root key Ks; and 
         [0013]    the MTC device, the BSF and the MTC-IWF generate K IWF  on the basis of the root key Ks in the GBA key agreement process. 
         [0014]    In an embodiment, the method may further include: before the AKA authentication between the MTC device and the BSF, 
         [0015]    the MTC device sends, to the BSF, an initialization request carrying MTC device identification information, MTC device SDT capability information and MTC device group identification information; 
         [0016]    after receiving the initialization request from the MTC device, the BSF sends, to the HSS, a retrieval request carrying the MTC device identification information and the MTC device group identification information; and 
         [0017]    the HSS determines whether the MTC device belongs to the MTC device group or not according to the MTC device identification information and the MTC device group identification information. 
         [0018]    In an embodiment, the method may further include: after generation of K IWF , 
         [0019]    data transmission is performed between the MTC device and the MTC-IWF according to K IWF . 
         [0020]    In an embodiment, 
         [0021]    the step that the HSS determines whether the MTC device belongs to the MTC device group or not may specifically include: 
         [0022]    the HSS determines whether the MTC device belongs to the MTC device group or not according to the MTC device identification information and the MTC device group identification information. 
         [0023]    In an embodiment, 
         [0024]    the step that the HSS determines whether the MTC device has the small data sending and receiving capability or not may specifically include: 
         [0025]    the HSS determines whether the MTC device has the small data sending and receiving capability or not according to the MTC device SDT capability information. 
         [0026]    In an embodiment, the step that the HSS determines whether the MTC device has the small data sending and receiving capability or not may specifically include: 
         [0027]    the HSS determines whether the MTC device has the small data sending and receiving capability or not according to stored subscription information, the subscription information including the MTC device SDT capability information. 
         [0028]    In an embodiment, the method may further include: after the step that K IWF  is generated on the basis of the root key Ks, 
         [0029]    the MTC device and the BSF generate a data encryption key and/or a data integrity protection key on the basis of K IWF , and send the data encryption key and/or data integrity protection key to the MTC-IWF. 
         [0030]    In an embodiment, the method may further include: after the HSS determines that the MTC device belongs to the MTC device group according to the MTC device identification information and the MTC device group identification information, 
         [0031]    the HSS generates user security configuration information according to the MTC device identification information and the MTC device group identification information. 
         [0032]    The embodiment of the disclosure provides a secure SDT method for an MTC device group, including: 
         [0033]    after at least one MTC device in the MTC device group creates a shared key K IWF  according to the method of the embodiment of the disclosure, in a GBA key agreement process between a further MTC device and an MTC-IWF: 
         [0034]    a BSF performs AKA vector authentication with the further MTC device according to a recently adopted authentication vector corresponding to an MTC device group identifier after determining that there is K IWF  being used according to MTC device group identification information and user security configuration information, and after authentication succeeds, the further MTC device and the BSF generate a root key Ks; and 
         [0035]    the further MTC device, the BSF and the MTC-IWF generate K IWF  on the basis of the root key Ks in the GBA key agreement process. 
         [0036]    The embodiment of the disclosure provides a secure SDT method for an MTC device group, including: 
         [0037]    after at least one MTC device in the MTC device group creates a shared key K IWF  according to a method of the embodiment of the disclosure and generates user security configuration information according to a method of the embodiment of the disclosure, in a GBA key agreement process between a further MTC device and an MTC-IWF: 
         [0038]    a BSF performs AKA vector authentication with the further MTC device according to a recently adopted authentication vector corresponding to an MTC device group identifier after determining that there is a data encryption key and/or data integrity protection key being used according to MTC device group identification information and the user security configuration information, and after authentication succeeds, the further MTC device and the BSF generate a root key Ks; and 
         [0039]    the further MTC device, the BSF and the MTC-IWF generate K IWF  on the basis of the root key Ks in the GBA key agreement process. 
         [0040]    The embodiment of the disclosure provides a secure SDT system for an MTC device group, which may be applied to AKA authentication between an MTC device in the MTC device group and a BSF, including the MTC device, the BSF and an HSS, in which: 
         [0041]    the HSS is configured to, after determining that the MTC device belongs to the MTC device group and has a small data sending and receiving capability, send an AKA authentication vector generated on the basis of an MTC device group key to the BSF; and 
         [0042]    the BSF is configured to perform AKA authentication with the MTC device according to the received AKA authentication vector. 
         [0043]    In an embodiment, the MTC device and the BSF may further be configured to generate a root key Ks after the AKA authentication between the BSF and the MTC device succeeds; and 
         [0044]    the MTC device, the BSF and an MTC-IWF generate the shared key K IWF  on the basis of the root key Ks in a GBA key agreement process. 
         [0045]    In an embodiment, before the AKA authentication between the MTC device and the BSF: 
         [0046]    the MTC device may further be configured to send, to the BSF, an initialization request carrying MTC device identification information, MTC device SDT capability information and MTC device group identification information; 
         [0047]    the BSF may further be configured to, after receiving the initialization request from the MTC device, send, to the HSS, a retrieval request carrying the MTC device identification information, MTC device SDT capability information and the MTC device group identification information; and 
         [0048]    the HSS may further be configured to determine whether the MTC device belongs to the MTC device group or not according to the MTC device identification information and the MTC device group identification information. 
         [0049]    In an embodiment, after K IWF  is generated on the basis of the root key Ks: 
         [0050]    the MTC device and the BSF may further be configured to generate a data encryption key and a data integrity protection key on the basis of K IWF , and send the data encryption key and/or data integrity protection key to the MTC-IWF. 
         [0051]    the HSS may further be configured to generate user security configuration information according to the MTC device identification information and the MTC device group identification information. 
         [0052]    In an embodiment, after K IWF  is generated on the basis of the root key Ks: 
         [0053]    the MTC device and the BSF may further be configured to generate the data encryption key and/or the data integrity protection key on the basis of K IWF , and send the data encryption key and/or data integrity protection key to the MTC-IWF. 
         [0054]    The embodiment of the disclosure provides a secure SDT system for an MTC device group, which may be applied to a GBA key agreement process between a further MTC device and an MTC-IWF after at least one MTC device in the MTC device group creates a shared key K IWF  according to a system of the embodiment of the disclosure, including the MTC device, a BSF and the MTC-IWF, in which: 
         [0055]    the BSF may be configured to perform AKA vector authentication with the MTC device according to a recently adopted authentication vector corresponding to an MTC device group identifier after determining that there is a data encryption key and data integrity protection key being used according to MTC device group identification information and user security configuration information, and after authentication succeeds, the MTC device and the BSF generate a root key Ks; and 
         [0056]    the MTC device, the BSF and the MTC-IWF may be configured to generate K IWF  on the basis of the root key Ks in the GBA key agreement process. 
         [0057]    The embodiment of the disclosure provides a secure SDT system for an MTC device group, which may be applied to a GBA key agreement process between a further MTC device and an MTC-IWF after at least one MTC device in the MTC device group creates a shared key K IWF  according to a system of the embodiment of the disclosure, including the MTC device, a BSF and the MTC-IWF, wherein 
         [0058]    the BSF may be configured to perform AKA vector authentication with the further MTC device according to a recently adopted authentication vector corresponding to an MTC device group identifier after determining that there is a data encryption key and/or data integrity protection key being used according to MTC device group identification information and user security configuration information, and after authentication succeeds, the further MTC device and the BSF generate a root key Ks; and 
         [0059]    the MTC device, the BSF and the MTC-IWF may be configured to generate K IWF  on the basis of the root key Ks in the GBA key agreement process. 
         [0060]    The embodiment of the disclosure provides an MTC device group, which may include: 
         [0061]    a storage module, configured to store MTC device identification information and MTC device group identification information; 
         [0062]    an initialization request sending module, configured to send, to a BSF, an initialization request carrying the MTC device identification information, MTC device SDT capability information and the MTC device group identification information; 
         [0063]    a first AKA authentication module, configured to perform AKA authentication with the BSF according to an AKA authentication vector, the AKA authentication vector being generated by an HSS on the basis of an MTC device group key; 
         [0064]    a first root key generation module, configured to, after the AKA authentication with the BSF succeeds, generate a root key Ks with the BSF; and 
         [0065]    a first key agreement module, configured to perform GBA key agreement with the BSF and an MTC-IWF. 
         [0066]    The embodiment of the disclosure provides a BSF, including: 
         [0067]    a first receiving module, configured to receive an initialization request from an MTC device, the initialization request carrying MTC device identification information MTC device SDT capability information and MTC device group identification information; 
         [0068]    a retrieval request sending module configured to, after receiving the initialization request from the MTC, send, to an HSS, a retrieval request carrying the MTC device identification information, MTC device SDT capability information and the MTC device group identification information; 
         [0069]    a second AKA authentication module, configured to perform AKA authentication with the MTC device according to an AKA authentication vector, the AKA authentication vector being generated by the HSS on the basis of an MTC device group key; 
         [0070]    a second root key generation module, configured to, after the AKA authentication with the MTC device succeeds, generate a root key Ks with the MTC device; and 
         [0071]    a second key agreement module, configured to perform GBA key agreement with the MTC device and an MTC-IWF. 
         [0072]    The embodiment of the disclosure provides an HSS, including: 
         [0073]    a second receiving module, configured to receive a retrieval request from a BSF, the retrieval request carrying MTC device identification information, MTC device SDT capability information and MTC device group identification information; 
         [0074]    a determination module, configured to determine whether an MTC device belongs to an MTC device group and has a small data sending and receiving capability or not; 
         [0075]    an authentication vector generation module, configured to, after the determination module determines that the MTC device belongs to the MTC device group and has the small data sending and receiving capability, generate an AKA authentication vector on the basis of an MTC device group key; and 
         [0076]    an authentication vector sending module, configured to send the generated AKA authentication vector to the BSF. 
         [0077]    The embodiment of the disclosure provides a BSF, including: 
         [0078]    a first receiving module, configured to receive an initialization request from an MTC device, the initialization request carrying MTC device identification information MTC device SDT capability information and MTC device group identification information; 
         [0079]    a first determination module, configured to determine whether there is a shared key K IWF  being used or not according to the MTC device group identification information and user security configuration information; 
         [0080]    a second AKA authentication module, configured to perform AKA vector authentication with the MTC device according to a recently adopted authentication vector corresponding to an MTC device group identifier; 
         [0081]    a second root key generation module, configured to, after AKA authentication with the MTC device succeeds, generate a root key Ks with the MTC device; and 
         [0082]    a second key agreement module, configured to perform GBA key agreement with the MTC device and an MTC-IWF. 
         [0083]    The embodiment of the disclosure provides a BSF, including: 
         [0084]    a first receiving module, configured to receive an initialization request from an MTC device, the initialization request carrying MTC device identification information MTC device SDT capability information and MTC device group identification information; 
         [0085]    a second determination module, configured to determine whether there is a data encryption key and/or data integrity protection key being used or not according to the MTC device group identification information and user security configuration information; 
         [0086]    a second AKA authentication module, configured to perform AKA vector authentication with the MTC device according to a recently adopted authentication vector corresponding to an MTC device group identifier; 
         [0087]    a second root key generation module, configured to, after AKA authentication with the MTC device succeeds, generate a root key Ks with the MTC device; and 
         [0088]    a second key agreement module, configured to perform GBA key agreement with the MTC device and an MTC-IWF. 
         [0089]    Compared with a conventional art, the method and system of the embodiment of the disclosure have the advantage that a technical problem about SDT between the MTC device in the MTC device group and the MTC-IWF is solved. In such a manner, for each SDT, any MTC device in the MTC device group may establish a secure SDT channel with the MTC-IWF according to the MTC device group information. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0090]      FIG. 1  is a diagram of an MTC device group-based secure SDT system according to an embodiment of the disclosure; 
           [0091]      FIG. 2  is a flowchart of an MTC device group-based shared key creation method for secure SDT according to embodiment 1 of the disclosure; 
           [0092]      FIG. 3  is a flowchart of an MTC device group-based shared key creation method for secure SDT according to embodiment 2 of the disclosure; 
           [0093]      FIG. 4  is an MTC device group-based shared key creation method for secure SDT according to embodiment 3 of the disclosure; 
           [0094]      FIG. 5  is a flowchart of an MTC device group-based shared key creation method for secure SDT according to embodiment 4 of the disclosure; 
           [0095]      FIG. 6  is a structure block diagram of an MTC device group-based secure SDT system according to embodiment 5 of the disclosure; 
           [0096]      FIG. 7  is a structure block diagram of a BSF according to embodiment 6 of the disclosure; and 
           [0097]      FIG. 8  is a structure block diagram of a BSF according to embodiment 7 of the disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0098]    The disclosure will be described below with reference to the drawings and embodiments in detail. It is important to note that the embodiments in the disclosure and characteristics in the embodiments may be combined under the condition of no conflicts. 
         [0099]    As shown in  FIG. 1 , a secure SDT system for an MTC device group in the disclosure includes: the MTC device group and a device in the MTC device group, the MTC device being configured to store MTC device group information and information about a shared key for SDT; a BSF, configured to perform a GBA key agreement process and store and maintain MTC user security configuration information; an HSS, configured to manage and maintain MTC device information and MTC device group information, generate the MTC user security configuration information and generate an AKA authentication vector on the basis of an MTC device group key; and an MTC-IWF, configured to implement a Network Attached Storage (NAS) server function, and store the MTC user security configuration information and the information about the shared key for SDT. 
       Embodiment 1 
       [0100]    In embodiment 1, an MTC device creates a shared key K IWF  with an MTC-IWF when being required to perform SDT, as shown in  FIG. 2 , specifically including the following steps. 
         [0101]    Step  200 : the MTC device (MTC device  1  in an MTC device group shown in  FIG. 2 ) sends an initialization request to a BSF, the initialization request including MTC device identification information, for example, an International Mobile Subscriber Identity (IMSI), and further including MTC device group identification information and small data sending/receiving capability information of the MTC device. 
         [0102]    Step  201 : the BSF sends a retrieval request to an HSS, the retrieval request including the MTC device identification information and the MTC device group identification information and further including the small data sending/receiving capability information of the MTC device. 
         [0103]    Step  202 : the BSF gets back, MTC user security configuration information and an AKA authentication vector generated on the basis of an MTC device group key, from the HSS according to the MTC device group identification information, that is, the HSS sends the MTC user security configuration information and the AKA authentication vector generated on the basis of the MTC device group key to the BSF. 
         [0104]    The HSS checks the MTC device identification information and MTC device group identification information in the retrieval request according to stored MTC device information and MTC device group information at first, and when it is determined that the MTC device belongs to the MTC device group, the HSS sends the MTC user security configuration information and the AKA authentication vector generated on the basis of the MTC device group key to the BSF; and in addition, when the HSS checks the MTC device identification information and MTC device group identification information in the retrieval request and after it is determined that the MTC device belongs to the MTC device group, the HSS may further check an SDT capability of the MTC device, for example, check a small data sending/receiving capability of the MTC device according to subscription information of the MTC device, to determine whether to send the MTC user security configuration information and the AKA authentication vector generated on the basis of the MTC device group key to the BSF or not. 
         [0105]    Step  203 : the BSF stores the received MTC user security configuration information and the received AKA authentication vector, and performs an AKA authentication process with the MTC device according to the received AKA authentication vector, and after the AKA authentication process is ended, the MTC device and the BSF generate a GBA root key Ks. 
         [0106]    Step  204 : the MTC device, an MTC-IWF and the BSF perform a GBA key agreement process, and the shared key K IWF  configured to protect SDT is generated between the MTC device and the MTC-IWF on the basis of the GBA root key Ks; and in addition, the BSF sends the MTC user security configuration information to the MTC-IWF for storage in the GBA key agreement process. 
       Embodiment 2 
       [0107]    In embodiment 2, an MTC device and an MTC-IWF further generate a small data encryption key and a small data integrity protection key on the basis of creating a shared key K IWF , as shown in  FIG. 3 , specifically including the following steps. 
         [0108]    Step  300 : the MTC device (MTC device  1  in an MTC device group shown in  FIG. 3 ) sends an initialization request to a BSF, the initialization request including MTC device identification information, for example, an IMSI, and further including MTC device group identification information and small data sending/receiving capability information of the MTC device. 
         [0109]    Step  301 : the BSF sends a retrieval request to an HSS, the retrieval request including the MTC device identification information and the MTC device group identification information and further including the small data sending/receiving capability information of the MTC device. 
         [0110]    Step  302 : the BSF gets back, MTC user security configuration information and an AKA authentication vector generated on the basis of an MTC device group key, from the HSS according to the MTC device group identification information, that is, the HSS sends the MTC user security configuration information and the AKA authentication vector generated on the basis of the MTC device group key to the BSF. 
         [0111]    The HSS checks the MTC device identification information and MTC device group identification information in the retrieval request according to stored MTC device information and MTC device group information at first, and when it is determined that the MTC device belongs to the MTC device group, the HSS sends the MTC user security configuration information and the AKA authentication vector generated on the basis of the MTC device group key to the BSF; and in addition, when the HSS checks the MTC device identification information and MTC device group identification information in the retrieval request and after it is determined that the MTC device belongs to the MTC device group, the HSS may further check an SDT capability of the MTC device, for example, check a small data sending/receiving capability of the MTC device according to subscription information of the MTC device, to determine whether to send the MTC user security configuration information and the AKA authentication vector generated on the basis of the MTC device group key to the BSF or not. 
         [0112]    Step  303 : the BSF stores the received MTC user security configuration information and the received AKA authentication vector, and performs an AKA authentication process with the MTC device according to the received AKA authentication vector, and after the AKA authentication process is ended, the MTC device and the BSF generate a GBA root key Ks. 
         [0113]    Step  304 : the MTC device, the MTC-IWF and the BSF perform a GBA key agreement process, and the shared key K IWF  configured to protect SDT is generated between the MTC device and the MTC-IWF on the basis of the GBA root key Ks. When generating K IWF , the BSF may further generate a next-level key, for example, an encryption key and an integrity protection key, configured to protect secure SDT through K IWF  according to a system requirement or an SDT security protection requirement, and then sends generated key information to the MTC-IWF for storage. In addition, the BSF sends the MTC user security configuration information to the MTC-IWF for storage in the GBA key agreement process. When generating K IWF , the MTC device may further generate the next-level key, such as the encryption key and the integrity protection key, configured to protect secure SDT through K IWF  according to the system requirement or the SDT security protection requirement. 
       Embodiment 3 
       [0114]    In embodiment 3, a further MTC device in an MTC device group creates a shared key K IWF  with an MTC-IWF when being required to perform SDT, as shown in  FIG. 4 , specifically including the following steps. 
         [0115]    Step  400 : the MTC device (MTC device  2  in the MTC device group shown in  FIG. 4 ) sends an initialization request to a BSF, the initialization request including MTC device identification information, for example, an IMSI, and further including MTC device group identification information and small data sending/receiving capability information of the MTC device. 
         [0116]    Step  401 : the BSF determines whether there is a key K IWF  being used or not according to the MTC device group identification information in the initialization request of the MTC device and MTC user security configuration information stored in the BSF. 
         [0117]    Step  402 : if it is determined that there is a key K IWF  being used, the BSF directly performs an AKA authentication process with the MTC device according to a recently adopted AKA authentication vector corresponding to an MTC device group identifier, and after the AKA authentication process is ended, the MTC device and the BSF generate a GBA root key Ks. 
         [0118]    Step  403 : the MTC device further generates the shared key K IWF  configured to protect SDT on the basis of the GBA root key Ks. 
       Embodiment 4 
       [0119]    In embodiment 4, when a further MTC device in an MTC device group is required to perform SDT, the MTC device further generates a small data encryption key and a small data integrity protection key which are shared with an MTC-IWF on the basis of a key K IWF , as shown in  FIG. 5 , specifically including the following steps. 
         [0120]    Step  500 : the MTC device (MTC device  2  in the MTC device group shown in  FIG. 5 ) sends an initialization request to a BSF, the initialization request including MTC device identification information, for example, an IMSI, and further including MTC device group identification information and small data sending/receiving capability information of the MTC device. 
         [0121]    Step  501 : the BSF determines whether there are an encryption key and an integrity key being used or not according to the MTC device group identification information in the initialization request of the MTC device and MTC user security configuration information stored in the BSF. 
         [0122]    Step  502 : if it is determined that there are an encryption key and an integrity key being used, the BSF directly performs an AKA authentication process with the MTC device according to a recently adopted AKA authentication vector corresponding to an MTC device group identifier, and after the AKA authentication process is ended, the MTC device and the BSF generate a GBA root key Ks. 
         [0123]    Step  503 : the MTC device further generates K IWF  on the basis of the GBA root key Ks. 
         [0124]    Step  504 : the MTC device further generates the encryption key and the integrity key which are configured to protect SDT on the basis of K IWF . 
       Embodiment 5 
       [0125]    The embodiment discloses a security SDT system for an MTC device group, as shown in  FIG. 6 , including an MTC device  10 , a BSF  20 , an MTC-IWF  30  and an HSS  40 , in which: 
         [0126]    the MTC device  10  includes: 
         [0127]    a storage module  11 , configured to store MTC device identification information and MTC device group information, the MTC device group information including MTC device group identification information and MTC device group key information; 
         [0128]    an initialization request sending module  12  configured to send, to the BSF  20 , an initialization request carrying the MTC device identification information and the MTC device group identification information; 
         [0129]    a first AKA authentication module  13 , configured to perform AKA authentication with the BSF  20  according to an AKA authentication vector, the AKA authentication vector being generated by the HSS  40  on the basis of an MTC device group key; 
         [0130]    a first root key generation module  14 , configured to, after the AKA authentication between the BSF  20  succeeds, generate a root key Ks with the BSF  20 ; and 
         [0131]    a first key agreement module  15 , configured to perform GBA key agreement with the BSF  20  and the MTC-IWF  30 . 
         [0132]    The BSF  20  includes: 
         [0133]    a first receiving module  21 , configured to receive the initialization request from the MTC device  10 , the initialization request carrying the MTC device identification information and the MTC device group identification information; 
         [0134]    a retrieval request sending module  22  configured to, after receiving the initialization request from the MTC device  10 , send, to the HSS  40 , a retrieval request carrying the MTC device identification information and the MTC device group identification information; 
         [0135]    a second AKA authentication module  23 , configured to perform AKA authentication with the MTC device  10  according to the AKA authentication vector, the AKA authentication vector being generated by the HSS  40  on the basis of the MTC device group key; 
         [0136]    a second root key generation module  24 , configured to, after the AKA authentication with the MTC device  10  succeeds, generate the root key Ks with the MTC device  10 ; and 
         [0137]    a second key agreement module  25 , configured to perform GBA key agreement with the MTC device  10  and the MTC-IWF  30 . 
         [0138]    The HSS  40  includes: 
         [0139]    a second receiving module  41 , configured to receive the retrieval request from the BSF  20 , the retrieval request carrying the MTC device identification information and MTC device group identification information; 
         [0140]    a determination module  42 , configured to determine whether the MTC device  10  belongs to the MTC device group and has a small data sending and receiving capability or not; 
         [0141]    an authentication vector generation module  43 , configured to, after the determination module  42  determines that the MTC device belongs to the MTC device group and has the small data sending and receiving capability, generate the AKA authentication vector on the basis of the MTC device group key; and 
         [0142]    an authentication vector sending module  44 , configured to send the generated AKA authentication vector to the BSF  20 . 
       Embodiment 6 
       [0143]    The embodiment discloses a BSF, as shown in  FIG. 7 , including: 
         [0144]    a first receiving module  21 , configured to receive an initialization request from an MTC device, the initialization request carrying MTC device identification information and MTC device group identification information; 
         [0145]    a first determination module  26 , configured to determine whether there is a shared key K IWF  being used or not according to the MTC device group identification information and user security configuration information; 
         [0146]    a second AKA authentication module  23 , configured to perform AKA vector authentication with the MTC device according to a recently adopted authentication vector corresponding to an MTC device group identifier; 
         [0147]    a second root key generation module  24 , configured to, after the AKA authentication with the MTC device succeeds, generate a root key Ks with the MTC device; and 
         [0148]    a second key agreement module  25 , configured to perform GBA key agreement with the MTC device and an MTC-IWF. 
       Embodiment 7 
       [0149]    The embodiment discloses a BSF, as shown in  FIG. 8 , including: 
         [0150]    a first receiving module  21 , configured to receive an initialization request from an MTC device, the initialization request carrying MTC device identification information and MTC device group identification information; 
         [0151]    a second determination module  27 , configured to determine whether there is a data encryption key and/or data integrity protection key being used or not according to the MTC device group identification information and user security configuration information; 
         [0152]    a second AKA authentication module  23 , configured to perform AKA vector authentication with the MTC device according to a recently adopted authentication vector corresponding to an MTC device group identifier; 
         [0153]    a second root key generation module  24 , configured to, after the AKA authentication with the MTC device succeeds, generate a root key Ks with the MTC device; and 
         [0154]    a second key agreement module  25 , configured to perform GBA key agreement with the MTC device and an MTC-IWF. 
         [0155]    The above are only the preferred embodiments of the disclosure and not intended to limit the scope of protection of the disclosure.