Abstract:
In order for effectively managing security of ProSe (Proximity based Services) communication, a server forming a communication system monitors locations of a plurality of UEs that are grouped to conduct direct communication with each other. The server manages security of the direct communication based on the locations.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to security management according to location change in ProSe (Proximity based Services). 
       BACKGROUND ART 
       [0002]    3GPP (3rd Generation Partnership Project) has started to study ProSe for both commercial and public safety uses. 
         [0003]    ProSe communication can provide services to UEs (more than one article of User Equipment) in proximity via an eNB (evolved Node B) or without the eNB. If the UEs are in proximity to each other, the UEs may able to use a “direct mode” path or “locally-routed” path. The “direct mode” path means that communication is conducted through direct links between the UEs. The “locally-routed” path means that communication is conducted through the eNB when the UEs are served by the same eNB (see e.g., NPL 1). 
       CITATION LIST 
     Non Patent Literature 
       [0004]    NPL 1: 3GPP TR 22.803, “Feasibility study for Proximity Services (ProSe) (Release 12)”, V12.2.0, 2013-06, Clause 4.1, pp. 10-11 
         [0005]    NPL 2: 3GPP TR 23.703, “Study on architecture enhancements to support Proximity Services (ProSe) (Release 12)”, V0.4.1, 2013-06, Clauses 4 and 6.1.4.1.3, pp. 7-11 and 31-32 
       SUMMARY OF INVENTION 
     Technical Problem 
       [0006]    While UEs are using ProSe service, some or all the UEs may move to a different location. Therefore, the inventors of this application have found that upon providing the ProSe service, there are the following problems: 
         [0007]    1) keep ProSe service and secure the ProSe service for the UEs are still in proximity; and 
         [0008]    2) prevent security context from being re-used by the UEs moved out of the proximity range of the given ProSe service and where the security context was established. 
         [0009]    Currently, there is no solution in 3GPP specifications. Note that NPL 2 merely discloses that a GMLC (Gateway Mobile Location Centre) can transmit location information of UEs to a ProSe server which supports the Prose communication. 
         [0010]    Accordingly, an exemplary object of the present invention is to provide a solution for effectively managing security of ProSe communication. 
       Solution to Problem 
       [0011]    In order to achieve the above-mentioned object, a server according to first exemplary aspect of the present invention includes: monitor means for monitoring locations of UEs (more than one article of User Equipment) that are grouped to conduct direct communication with each other; and management means for managing security of the direct communication based on the locations. 
         [0012]    Further, a UE according to second exemplary aspect of the present invention is grouped with different UEs to conduct direct communication with each other. This UE includes: update means for updating a session key used for the direct communication in response to reception of an instruction from a server, the instruction being issued when the server detects that one or more UEs among the different UEs have moved out of a range of the group; and request means for requesting remaining UEs to update the session key. 
         [0013]    Further, a UE according to third exemplary aspect of the present invention is grouped with different UEs to conduct direct communication with each other. This UE includes removal means for removing a session key used for the direct communication in response to reception of an instruction from a server, the instruction being issued when the server detects that the UE has moved out of a range of the group. 
         [0014]    Further, a communication system according to fourth exemplary aspect of the present invention includes: a plurality of UEs that are grouped to conduct direct communication with each other; and a server that monitors locations of the plurality of UEs, and manages security of the direct communication based on the locations. 
         [0015]    Further, a method according to fifth exemplary aspect of the present invention provides a method of controlling operations in a server. This method includes: monitoring locations of UEs that are grouped to conduct direct communication with each other; and managing security of the direct communication based on the locations. 
         [0016]    Further, a method according to sixth exemplary aspect of the present invention provides a method of controlling operations in a UE that is grouped with different UEs to conduct direct communication with each other. This method includes: updating a session key used for the direct communication in response to reception of an instruction from a server, the instruction being issued when the server detects that one or more UEs among the different UEs have moved out of a range of the group; and requesting remaining UEs to update the session key. 
         [0017]    Furthermore, a method according to seventh exemplary aspect of the present invention provides a method of controlling operations in a UE that is grouped with different UEs to conduct direct communication with each other. This method includes removing a session key used for the direct communication in response to reception of an instruction from a server, the instruction being issued when the server detects that the UE has moved out of a range of the group. 
       Advantageous Effects of Invention 
       [0018]    According to the present invention, it is possible to solve the above-mentioned problems, and thus to provide a solution for effectively managing security of ProSe communication. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0019]      FIG. 1  is a block diagram showing a configuration example of a communication system according to an exemplary embodiment of the present invention. 
           [0020]      FIG. 2  is a diagram showing a first example of scenarios of how UEs change locations. 
           [0021]      FIG. 3  is a diagram showing a second example of scenarios of how UEs change locations. 
           [0022]      FIG. 4  is a diagram showing a third example of scenarios of how UEs change locations. 
           [0023]      FIG. 5  is a sequence diagram showing a first operation example of the communication system according to the exemplary embodiment. 
           [0024]      FIG. 6  is a sequence diagram showing a second operation example of the communication system according to the exemplary embodiment. 
           [0025]      FIG. 7  is a sequence diagram showing a third operation example of the communication system according to the exemplary embodiment. 
           [0026]      FIG. 8  is a block diagram showing a configuration example of a server according to the exemplary embodiment. 
           [0027]      FIG. 9  is a block diagram showing a configuration example of a UE according to the exemplary embodiment. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0028]    Hereinafter, an exemplary embodiment of a server and a UE according to the present invention, and a communication system to which these server and UE are applied, will be described with the accompany drawings. 
         [0029]    As shown in  FIG. 1 , a communication system according to this exemplary embodiment includes a plurality of UEs  10 _ 1  to  10 _ n  (hereinafter may be collectively referred to by a code  10 ), a ProSe server  20 , an E-UTRAN (Evolved Universal Terrestrial Radio Access Network)  30 , and a EPC (Evolved Packet Core)  40 . The E-UTRAN  30  is formed by one or more eNBs (not shown). The EPC  40  includes, as its network nodes, an MME (Mobility Management Entity)  41  which manages mobility of the UEs  10 _ 1  to  10 _ n , and a GMLC  42  which stores location information of the UEs  10 _ 1  to  10 _ n.    
         [0030]    The UE  10  attaches to the EPC  40  thorough the E-UTRAN  30 , thereby functioning as a typical UE. Moreover, the UE  10  uses the above-mentioned “direct mode” path, thereby conducting ProSe communication. Note that the UE  10  may use the above-mentioned “locally-routed” path. 
         [0031]    The ProSe server  20  can communicate with the GMLC  42  to monitor the location information of the UE  10 . Moreover, as will be described later, the ProSe server  20  manages security of the ProSe communication based on the location information. 
         [0032]    Next, operation examples of this exemplary embodiment will be described in detail with reference to  FIGS. 2 to 7 . Note that configuration examples of the ProSe server  20  and the UE  10  will be described later with reference to  FIGS. 8 and 9 . 
         [0033]    In this exemplary embodiment, assume that ProSe service is in use for a group of UEs  10 _ 1  to  10 _ n , and the security context is established. The following scenarios of how location change happens are considered: 
         [0034]    1) None of UEs has location change (hereinafter, referred to as “Case 1”); 
         [0035]    2) All of the UEs have changed location, but they stay in proximity to each other within a predetermined distance (hereinafter, referred to as “Case 2”); 
         [0036]    3) One or more UEs (travelers) have moved out of proximity from other UEs and they do not use ProSe service (hereinafter, referred to as “Case 3”); and 
         [0037]    4) One or more UEs have moved out of proximity from the UEs and they want to keep ProSe service among the travelers (hereinafter, referred to as “Case 4”). 
         [0038]    In order to know if the UEs  10 _ 1  to  10 _ n  have moved, the ProSe Server  20  can request the GMLC  42  to send location information of the UEs  10 _ 1  to  10 _ n  periodically when the ProSe service is activated for the UEs. Each time the ProSe Server  20  receives the location of the group member of UEs  10 _ 1  to  10 _ n , the ProSe Server  20  compares the location with the previous location information that the ProSe Server  20  stores. 
         [0039]    Further, assume that one of the UEs  10 _ 1  to  10 _ n  functions as a group manager in the group. The location of group manager is taken as the Origin of the coordinate, to determine whether other UEs are in proximity. 
       &lt;Operations in Case 1&gt; 
       [0040]    If the location information sent from the GMLC  42  is the same with the previous location information, the ProSe Server  20  determines the group location is not changed and no group management or security needs to be updated. 
       &lt;Operations in Case 2&gt; 
       [0041]    If the location information sent from the GMLC  42  shows that all of UEs  10 _ 1  to  10 _ 5  shown in  FIG. 2  have changed their location, but they are still in the same range compared to the group manager, no group management or security needs to be updated according to the location change. However, all members can update keys normally even when they are in different location. 
       &lt;Operations in Case 3&gt; 
       [0042]    If the location information sent from the GMLC  42  shows that as shown in  FIG. 3 , some UEs  10 _ 4  and  10 _ 5  are out of proximity range and the moved UEs  10 _ 4  and  10 _ 5  do not want to or cannot keep the ProSe service, group and security management needs update. 
       &lt;Operations in Case 4&gt; 
       [0043]    If the location information sent from the GMLC  42  shows that as shown in  FIG. 4 , some UEs  10 _ 4  and  10 _ 5  are out of proximity range and the traveler UEs  10 _ 4  and  10 _ 5  want to keep ProSe service between themselves instead, the group and security management needs update. 
         [0044]    In the following two sections, detail description of operations in Case 3 and Case 4 will be given. In both cases, assume that the UE  10 _ 1  is the group manager, and the UEs  10 _ 3  and  10 _ 4  left the group. 
       1. Group and Security Management for Case 3 
       [0045]    Assume that the UEs  10 _ 1  to  10 _ 5  were in the same ProSe group. The UEs  10 _ 3  and  10 _ 4  are not in proximity with the UE  10 _ 1 ,  10 _ 2  and  10 _ 5  anymore. The ProSe Server  20  determines that the UE  10 _ 3  and  10 _ 4  do not use ProSe service, according to capabilities of the UE  10 _ 3  and  10 _ 4 , and policy for ProSe service. The ProSe Server  20  will inform the remained group UEs  10 _ 1 ,  10 _ 2  and  10 _ 5  that the UE  10 _ 3  and  10 _ 4  left the group and are no more available for the ProSe service. 
         [0046]    Group and security management is different when the group is temporary or dedicated. 
         [0047]    When the group is temporary or the UEs  10 _ 3  and  10 _ 4  are temporary members, the group does not expect the UE  10 _ 3  and  10 _ 4  to return and resume the ProSe service. Any UE joins the group is considered as a new member. In order to prevent the keys from being reused, the remained group member of UEs will need new session keys. The UEs  10 _ 3  and  10 _ 4  remove the session keys. The session keys are a pair of confidentiality and integrity keys. 
         [0048]    On the other hand, when the group is dedicated or the UEs  10 _ 3  and  10 _ 4  are dedicated members, the UEs  10 _ 3  and  10 _ 4  may return to the group. The group manager can decide to update the group and security management after a period of time. This is done by starting a timer after the group manager is indicated that the UEs  10 _ 3  and  10 _ 4  left the group. The UEs  10 _ 3  and  10 _ 4  will remove the session keys after the period time when they will not return to the group. This is to prevent the UEs  10 _ 3  and  10 _ 4  from using the key to perform direct discovery and communication without network authorization. 
         [0049]    In the temporary case, as shown in  FIG. 5 , the GMLC  42  obtains UEs location information, following normal procedure (step S 11 ). 
         [0050]    Then, the GMLC  42  provides the UEs location information to the ProSe Server  20  with group ID, UE IDs, location and the time when the location was detected (step S 12 ). This can be periodical according to network and/or group setting. 
         [0051]    The ProSe Server  20  compares the current location with previous location, to determine which UEs moved out of group range (step S 13 ). 
         [0052]    If the ProSe Server  20  detected that the UEs  10 _ 3  and  10 _ 4  moved out of group range, the ProSe Server  20  sends Status Update to the group manager UE  10 _ 1 , indicating IDs of the UEs  10 _ 3  and  10 _ 4 , group ID and status of left the group (step S 14 ). 
         [0053]    The ProSe Server  20  also sends Status Update to the UEs  10 _ 3  and  10 _ 4  with their ID (IDs of the UEs  10 _ 3  and  10 _ 4 ), group ID and status of out of range (step S 15 ). 
         [0054]    The UEs  10 _ 3  and  10 _ 4  will remove the session keys (step S 16 ). 
         [0055]    The UEs  10 _ 3  and  10 _ 4  optionally report to the ProSe server  20  that the session keys are removed (step S 17 ). 
         [0056]    The group manager UE  10 _ 1  derives new session keys from a key Kp (step  18 ). The key Kp is a key related to the group and also may related to the ProSe server  20 . 
         [0057]    The group manager UE  10 _ 1  sends Update session key request to the remained group member (step S 19 ). The UEs  10 _ 2  and  10 _ 5  are the remained member here. The request includes algorithm, indicator KSI (Key Set Identifier)_p related to the key Kp, and other parameters for session key derivation. The message is confidentiality and integrity protected with the current session keys. 
         [0058]    The remained member UEs  10 _ 2  and  10 _ 5  derive new session keys separately (step S 20 ). 
         [0059]    The UEs  10 _ 2  and  10 _ 5  send Update session key Ack (Acknowledge) to group manager UE  10 _ 1  (step S 21 ). This message is confidentiality and integrity protected with the new session keys. 
         [0060]    In the dedicated case, as shown in  FIG. 6 , a timer is set and allocated to dedicated group members when the current session key is activated (step S 31 ). 
         [0061]    Steps S 32  to  36  are the same with Steps S 11  to S 15  shown in  FIG. 5 . 
         [0062]    The timer is started when UEs receive the indication that the UEs  10 _ 3  and  10 _ 4  are out of range. The session keys remain till the timer has expired (step S 37 ). 
         [0063]    When the timer has expired, the UEs  10 _ 3  and  10 _ 4  will remove the session keys (step S 38 ). 
         [0064]    The UEs  10 _ 3  and  10 _ 4  optionally report to the ProSe server  20  that the session keys are removed (step S 39 ). 
         [0065]    When the timer has expired at step S 37 , the group manager UE  10 _ 1  derives new session keys from the key Kp (step S 40 ). 
         [0066]    Steps S 41  to S 43  are the same with steps S 19  to S 21  shown in  FIG. 5 . 
         [0067]    The Status Update message is confidentiality and integrity protected. 
       2. Group and Security Management for Case 4 
       [0068]    Assume that the UEs  10 _ 1  to  10 _ 5  were in the same ProSe group. The UEs  10 _ 3  and  10 _ 4  are not in proximity with the UEs  10 _ 1 ,  10 _ 2  and  10 _ 5  anymore. The UEs  10 _ 3  and  10 _ 4  will use ProSe service between them. The ProSe Server  20  will inform the remained group UEs that the UEs  10 _ 3  and  10 _ 4  left the group. The ProSe Server  20  will also inform the UEs  10 _ 3  and  10 _ 4  that they are out of range from the previous group. The ProSe server  20  can determine that the UEs  10 _ 3  and  10 _ 4  can still use ProSe service with each other. 
         [0069]    There are two ways for the UEs  10 _ 3  and  10 _ 4  to keep communication: 1) they can create a new group with a new group ID and derive new session keys; 2) they can use the same group ID but change their session keys. The first case is depicted in  FIG. 7  and figure for the second case is omitted. 
         [0070]    As shown in  FIG. 7 , the GLMC  42  obtains UEs location information (step S 51 ). 
         [0071]    Then, the GMLC  42  provides the UEs location information to the ProSe server  20  with group ID, UE IDs, location and the time when the location was detected (step S 52 ). This can be periodical according to network and/or group setting. 
         [0072]    The ProSe server  20  compares the current location with previous location, to determine which UEs moved out of group range (step S 53 ). 
         [0073]    If the ProSe server  20  detected that the UEs  10 _ 3  and  10 _ 4  moved out of group range, the ProSe server  20  sends Status Update to the group manager UE  10 _ 1 , indicating IDs of the UEs  10 _ 3  and  10 _ 4 , group ID and status of left the group (step S 54 ). 
         [0074]    The ProSe server  20  also sends Status Update to the UEs  10 _ 3  and  10 _ 4  with their ID (IDs of the UEs  10 _ 3  and  10 _ 4 ), group ID and status of out of range (step S 55 ). 
         [0075]    The UEs  10 _ 3  and  10 _ 4  request to continue their ProSe Service with each other, by sending ProSe Service Continue Request, contain the other UE ID, service ID (step S 56 ). 
         [0076]    The ProSe server  20  performs verification if the UEs  10 _ 3  and  10 _ 4  are allowed to continue to have ProSe service, and then derives a new Kp (step S 57 ). 
         [0077]    The ProSe server  20  sends ProSe Service Continue Response to the UEs  10 _ 3  and  10 _ 4 , with IDs of the UEs  10 _ 3  and  10 _ 4 , service ID, Kp, and new group ID (step S 58 ). 
         [0078]    The UEs  10 _ 3  and  10 _ 4  derive session keys from the Kp they received (step S 59 ). 
         [0079]    The UEs  10 _ 3  and  10 _ 4  use the session key to continue their group communication (step S 60 ). 
         [0080]    The UE  10 _ 1 , and other remained group member UEs  10 _ 2  and  10 _ 5  update their session keys as with in Case 3 (step S 61 ). 
         [0081]    The Status Update, ProSe Service Continue Request, and ProSe Service Continue Response message are confidentiality and integrity protected. 
       3. Location Information Verification 
       [0082]    The GMLC  42  can send UEs location information to the ProSe server  20 : 
         [0083]    1) Periodically, the frequency can be set by the ProSe server  20  for given group and/or the service; 
         [0084]    2) any time it receives a report from MME/SGSN; and 
         [0085]    3) at ProSe Server request. 
         [0086]    The location information contains the location information of all group members, the group ID, UE ID, each UE&#39;s location. The ProSe server  20  stores the previous location information. 
         [0087]    After received the current location information, the ProSe server  20  compares the previous and current location, and compares the member UEs location information with group manager location, to see if UEs are still in the range. This means, the location of group manager is used as the origin to determine whether UEs are in the group range. 
         [0088]    According to this exemplary embodiment, it is possible to achieve the following advantageous effects (1) to (4), for example. 
         [0089]    (1) ProSe Server can support group management and indicate the UEs whether they are still in proximity. 
         [0090]    (2) Group manager can decide whether to derive new session key or keep the current session keys, depend on the group member status. This can prevent the session keys being maliciously reused. 
         [0091]    (3) Group manager can update session keys and indicate other remained group members to do the same. 
         [0092]    (4) UEs which moved out of the group range can continue to use ProSe service with ProSe Serve support. 
         [0093]    Next, configuration examples of the ProSe server  20  and the UE  10  according to this exemplary embodiment will be described with reference to  FIGS. 8 and 9 . 
         [0094]    As show in  FIG. 8 , the ProSe server  20  includes a monitor unit  21  and a management unit  22 . The monitor unit  21  monitors locations of the UEs  10 _ 1  to  10 _ n  shown in  FIG. 1 , by periodically acquiring the location information from the GMLC  42 , for example. The management unit  22  manages security of the ProSe communication between the UEs  10 _ 1  to  10 _ n  based on the locations, as shown in  FIGS. 5 to 7 . Note that these units  21  and  22  are mutually connected with each other through a bus or the like. These units  21  and  22  can be configured by, for example, a transceiver which conducts communication with the UEs  10 _ 1  to  10 _ n  through the E-UTRAN  30  and the EPC  40 , and a controller such as a CPU (Central Processing Unit) which controls this transceiver. 
         [0095]    As show in  FIG. 9 , the UE  10  includes an update unit  11  and a request unit  12 , in a case of functioning as the group manager. The update unit  11  updates the session keys in response to the Status Update message from the ProSe server  20 , when the Status Update message indicates that one or more UEs in the group have moved out of the range of the ProSe communication. The request unit  12  sends the Update session key request to the remained group member UEs. 
         [0096]    As substitutes for or in addition to the units  11  and  12 , the UE  10  can include a removal unit  13 , a request unit  14 , and a derivation unit  15 . The removal unit  13  removes session keys in response to the Status Update message from the ProSe server  20 , when the Status Update message indicates that the UE  10  itself has moved out of the range of the ProSe communication. The request unit  14  sends the ProSe Service Continue Request to the ProSe server  20 . The derivation unit  15  derives new session keys upon receiving the ProSe Service Continue Response from the ProSe server  20 . 
         [0097]    Note that these units  11  to  15  are mutually connected with each other through a bus or the like. These units  11  to  15  can be configured by, for example, a transceiver which conducts communication with the ProSe server  20  through the E-UTRAN  30  and the EPC  40 , and a controller such as a CPU which controls this transceiver. 
         [0098]    Note that the present invention is not limited to the above-mentioned exemplary embodiment, and it is obvious that various modifications can be made by those of ordinary skill in the art based on the recitation of the claims. 
         [0099]    The whole or part of the exemplary embodiment disclosed above can be described as, but not limited to, the following supplementary notes. 
       (Supplementary Note 1) 
       [0100]    GMLC sends UE location information to ProSe Server, periodically, when it receives report from MME/SGSN or at ProSe Server request. 
       (Supplementary Note 2) 
       [0101]    ProSe Server stores UE previous location and compare the current location with its previous location and also with the group manager location to determine whether any group member has move out of group range. 
       (Supplementary Note 3) 
       [0102]    ProSe Server indicates the group manager and UEs which moved out of range about the location change. 
       (Supplementary Note 4) 
       [0103]    Group manager update session keys and indicate other remained members to do the same by sending Update session key request. 
       (Supplementary Note 5) 
       [0104]    Dedicated member UEs can have a timer related to the session key deployed when the session key was derived. The timer starts when UEs are out of range, and UEs can keep the session key till the timer has expired. 
       (Supplementary Note 6) 
       [0105]    UEs which move out of group range request to continue ProSe service with each other, by sending ProSe Service Continue Request. 
       (Supplementary Note 7) 
       [0106]    ProSe Server determines whether the above mentioned UEs can continue ProSe service with each other, by sending ProSe Service Continue Response. 
         [0107]    This application is based upon and claims the benefit of priority from Japanese patent application No. 2013-223326, filed on Oct. 28, 2013, the disclosure of which is incorporated herein in its entirety by reference. 
       REFERENCE SIGNS LIST 
       [0000]    
       
           10 ,  10 _ 1 - 10 _ n  UE 
           11  UPDATE UNIT 
           12 ,  14  REQUEST UNIT 
           13  REMOVAL UNIT 
           15  DERIVATION UNIT 
           20  ProSe SERVER 
           21  MONITOR UNIT 
           22  MANAGEMENT UNIT 
           30  E-UTRAN 
           40  EPC 
           41  MME 
           42  GMLC