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详细说明：NULL 博文链接：https://ansonlai.iteye.com/blog/801810Presence model has been chosen for this project not have intended 3). How can SIP model meet privacy requirements? a suitable mechanism is designed to fulfill the privacy D LBS needs feedback requirements with respect to RFC3261, RFC3265 and It is important for a user to know his/her actual level of RFC3856 nformation disclosure. Users may have difficulty accepting a system into their privacy practice if the scope of it B Research methodology privacy implications is unclear. With feedback mechanisms, The methodology of this project is based on a proof of a system could provide social visibility to prevent misuse concept and prototype approach. a prototype is developed [9]. For example, Alice is less likely to repeatedly query to investigate the feasibility of the concept. We use an Bob's location if she knows that Bob can see each of her exploratory prototype process to perform rapid development requests. A user will feel comfortable with the capability to of a system, where an initial prototype is produced and control his sensitive information and the ability to know the refined through a number of stages towards the final system. actual information disclosure Overall, the steps include: requirements analysis, rapid E LBS needs special exceptions for emergencies design and implementation, using and verification of the In crisis situations, safety far outweighs privacy needs prototype, refine the prototype when the prototype is not An emergency should be given privilege to be treated in a adequate, and finally deliver the system special manner. IP telephony can support emergency situations as with e911 call services in USA. 110 in Germany, and 1 12 in the rest of Europe [5]. Hospitals, for V. THE KEY PRIVACY REQUIREMENT example, may require up-to-date information about the A LBS needs dynamic response to circumstance location of patients, particularly when medical emergencies With regard to geographic in formation disclosure, a arise. Trusted proxies are sometimes used to handle these Notifiers willingness to reveal his/her information primarily kinds of situations. People are willing to pay for this service depends on who is requesting that information and why For example, the MedicAlert is a paid service that stores Depending on the social relationship between a Notifier and personal medical records and forwards it to emergency a Subscriber, a response might be quite different from one responders in the case of medical emergencies user to another. As Roach pointed out, while traditional approaches understand privacy as a state of social VL. SYSTEM DESIGN AND IMPLEMENTAION withdrawal"[14]. Altman instead sees it as a dialectic and A. System design dynamic boundary regulation process [1]. Privacy For our SIP-based approach to privacy and LBs, we use a management is not about setting rules and enforcing them. Peer-to-Peer(P2P) architecture and authorization Rather, it is the continual management of boundaries mechanism. In order to prevent unnecessary information between different spheres of action and degrees of from being revealed to a third party, we use sIP Back-to- disclosure within those spheres. Back User Agents(B2BUA)as end points [16 A B2BUA processes incoming requests and generates outgoing B LBS needs a level of deniability built in requests to communicate with another B2BUA. Once a P2P Hindus et al have suggested a social need to avoid connection has been built up, a proxy hands over the data potentially embarrassing situations, undesired intrusions, transfer between the two nodes. Geographic location and unwanted social obligations [ 8. A good example of this information is collected into a B2BUA where as much is with mobile phones. If a person does not answer a mobile personal information about an end user is captured, stored, all, it could be for technical reasons--such as being and processed on local devices owned by that end user outside of the service range, not having the phone with RFC 3265 states: "Privacy concerns may require that him/her, or the phone was offor for social reasons, such as Notifiers apply policy to determine whether a particular being busy or not wanting to talk to the caller at that Subscriber is authorized to subscribe to a certain set of moment. The result is that the person being called has a events. Such policy may be delined by mechanisms such as simple model for protecting his/her privacy, while the caller access control lists or real-time interaction with a user [14] cannot tell why that person is not answering. By default, it Whenever a B2BUA sends a Subscribe request to another does"the right thing "without the end-user having to take B2BUA, it will trigger real-time authorization process with ial action a user. On a peer-to-peer level, B2BUAs authorize one another personally C LBS needs coarse-grained control LBS need coarse-grained control. A LBS user should 1) Components have a way to stop or adjust the information disclosure to The system architecture is shown in Figure 1. It includes the level that users want to reveal to the others. Lederer and Sip proxy, Domain Name System(DNS)server, Presentit Hong suggest that ubiquitous computer systems that convey and Watcher. The sip proxy is used to forward a SIP location information could incorporate both a precision dial message and to the desired Presentity. The dNs server is (ordinal)and a hide button (binary), e. g, audio device used to find the next-hop IP address. A Presentity is a volume and mute controls, so users can either adjust the presence model entity. It is the lpidf owner that sends precision at which their context is disclosed or decidedly geographic information to Watchers. A Watcher is a halt disclosure [11]. This helps users to accommodate the Presence model entity that subscribes to receive the LpidF controls and even co-opt them in ways that the designer may from a Presentity in order to learn that Presentity's geographic information ecure and self-contained furthermore Lpidf has to fulfill user needs and meet the privacy requirements 2) Routing the Request The basic unit of storage in an LPidF document is the SIP networks are capable of routing requests from any tuple. A LPIDF document might contain more than one user on the network to the server that holds the registration tuple. a tuple is used to describe individual pieces of state for a user [15]. SIP uses hybrid P2P architecture. Its contextual data. For example, a LPIDF might contain static features include information such as a name and email address. as well as Lookup centralized: siP provides a mechanism for a user dynamic information such as current location and activity Agent (UA) to explicitly create a binding. This mechanism A SIP Presence LBS application retrieves and manipulates is known as registration. Registration entails sending a LPIDF data to accomplish location-aware tasks through end REGISTER request to a special type of User Agent Server users specify privacy preferences qUAS) known as a registrar. A registrar acts as the front end C Proposed SIP flow meets privacy requirements Figure 2 shows our proposed Sip message flow s口rtc。l SUBSCRIBE and notify methods are used to deal with NS N∞n-S| P protoc。l most of presence location issues, and PUBLISH is used to deal with an emergency situation. The SIP authorization mechanism is applied to prevent sensitive information from being revealed. We can now examine our prototype in light of the key privacy requirements defined in section V JAIN P Proxy JIN 1). Dynamic response to circumstance? Watche When a Subscriber wishes to subscribe to a particular PrEsentIty S段18 state for a resource, it forms a SUBSCRIBE message. The SUBSCRIBE request will be confirmed with a final response. 200-class responses indicate that the subscription Fig 1. Proposed system architecture has been accepted, and that a NoTiFY will be sent Step 1-5 a watcher sends SUBSCRIBE Request Presenti immediately. A 202 response merely indicates that the through SiP proxies and dNs server subscription has been understood, and that authorization Step6-8 Desired Presentity reply 200 ok back to Watcher Finally, a dialog is established between Watcher and may or may not have been granted. Whenever a request Presentity for peer-to-peer message exchange comes, a Presentity should be able to accept or deny the request, and reveal part of the geographic location to the dns server for a domain, reading and writing mappings based on the contents of REGISTER requests. A Subscriber(Alice) SIP Proxy Notifier( Bob) proxy server that is responsible for routing requests for that Step 1----Subscribe----->1--Subscribe---> Request state subscription domain typically consults this dNS server Data exchange between peers. If a user wants Lo initiate a session with another user. SIP must discover the current Step 3 K-----------NOTIFY (pending)----- Waiting for authorization host(s) at which the destination user is reachable. This Step 4 200ok 7l Acknowledge notifying discovery process is frequently accomplished by SIP step5-… NOTIFY( active Grand city level information network elements such as proxy servers and redirect servers Step 6 200 ok-------------l Acknowledge notifying that are responsible for receiving a Request, determining where to send it based on know ledge of a registrar and dNS PUA (Alice) SIP Proxy Watcher(Hospital) server, and then sending it there. When a SUBSCRIBE step7卜-Push-叫 I update emergency infomation message reaches the Presentity, it establishes a"dialog"with Step 8 (<--200 ok- I Acknowledge publication the presence agent. a dialog is defined in RFC 3261, and it ----Notify-----> Inform emergency informatio represents the SIp state between a pair of entities to facilitate peer-to-peer(P2P)message exchanges [16 Step 10 I <-----200 ok---- Acknowledge notifying Fig 2. Proposed SIp message flow Alice sends SUBSCRIBE Request to Bob asking for his B. Location-enhanced PIDF(LPIDF geographic information. Notifier reply 202 Response indicates LPIDF is a extension of pidf defined as a data format that the subscription has been understood, and that an for containing geographic information. SIP, by itself, only authorization request needs to be approved by Bob. Bob provides call control. However, SIP accepts additional authorizes the request and decided to reveal his city level information inserted as a siP payload for other applications ographic information to Al Geographic information in the LPidF format can be inserted When Alice encounters an emergency situalion, Presence into a SIP message's payload. The basic function of LPIDF User Agent (PUA)publishes her geographic information to is to provide a common and extensible container where the SIP proxy, and SIP Proxy notifies hospital user can place identifiers, security factors, location information to the Subscriber. SIP provides the representation, and other parameters to manage the users authorization mechanism to dynamically accept or deny an location informalion. The requirement for the LPidf is to incoming SUBSCRIBE request. The authorization mechanism is used to provide real-time interaction. Hence, a system architecture shown in Figure 1. The prototype user can give dynamic responses for the incoming requests. solution uses SIP mechanism implemented with the Java The current project offers three options for users: SIP Application Programming Interface(API). The presence authorize","authorize with privacy concern" and"reject service has two distinct sets of clients One set of clients 2)Level of deniability? called Presentities, provides the presence information to be A NOTIFY request will be sent to a Subscriber after stored and distributed. The other set of clients, called sending a 202 response. RFC 3265 specifies that s NOTIFY Watchers, receives the presence information from the message is sent immediately after any 200-class response to service. we use the jsr32 SiP APi to develop the presentity a SUBSCRIBE request, regardless of whether the and use the JSr 180 SIP API to develop the watcher for this subscription has already been authorized. 200-class prototype The JAIN-SIP proxy is used to test the Presentit responses to SUBSCRIBE requests do not generally contain and the watcher and to forward sip requests. The Nokia any useful information beyond subscription duration. Their $60 emulator was used to run Java 2 Micro Edition(J2ME) primary purpose is to serve as a reliability mechanism. The code. The prototype is shown in Figure 3 NOTIFY requests must contain a "Subscription-State header with a value of active,,"pending,, or"terminated. Presentity is at the left hand side of figure 3 The"pending"value indicates that the subscription has been The Presentity capabilities are received, but that policy information is insufficient to accept a Send and process notify and subscriBe requests or deny the subscription at this time. This approach provides o Support XML format""lpidf+xml a degree of deniability, as a"Subscription-State"might be Register and unregister to a SIP proxy pending"due to technical failures, lack of actual data, o Authorize nechanism for incoming SUBSCRIBE request restricted access, or because some other possible reason o Modify LPIDF data for coarse-grained control BCoarse-grained control? Watcher is at the right hand side offigure 3 When the authorization has been approved, a user can The Watcher capabilities are: o Send and process NOTiFY and SUBSCRIBE requests decide which parts of the LPiDF he/she wants to reveal. we o Support XML format"lpidf+ xml" define five levels:"country","province,"city o Register and unregister to a SIP proxy and"room. Meanwhile, another two parameters have been o Send PUBLiSh request to SIP proxy provided: Durationand"Interval". The user can decide how long he/she wants to reveal the geographic in fornation (for instance, 2 hours), and the user can delermine the You arcOFFUNE Watcher interval for releasing the geographic information (for Contact SIP URL ilsonmotilanist oDy instance, once every 5 minutes) 4). User feedback? s 90v (orINn JAIN SIP PROXY abound pew IP a和 The Notifier contains a dynamic subscription list. When a PIR subscription is created in the Notifier. it stores the event 车② package name and the“ Event” header“id” parameter as part ,·画甲 hiE proxy view the traces of the subscription information into the Notifier. A subscription is destroyed when a Notifier sends a NotifY Request with Subscription- State”of“ terminated 1= According to the subscription list, our SIP Presence LBs is umt able to indicale who is gelling geographic infornation and how much geographic information the Subscriber is getting When a subscription is terminated, it is removed from the郾sny6如6》国。83 subscription list. Thus, the Presence LBs application will Fig 3. Java Implementation reflect that the Subscriber stopped getting geographic Watcher sends SUBSCRIBE Request to Presentity asking information from a notifier for geographic information. Authorization needs to be taken 5). How to deal with emergency situations by PresentiLy. Presentity needs to decide the "level duration”and“ interval”o geogra hic information a Presence User Agent(PUA) pushes disclosure presence system, but it is outside of the system. In that way the pua does not receive SUBSCribe messages or send NOTIFY messages. [ 12] provides a method, PUBLISH, to VIL CONCLUSION push the geographic lo cation information to a proxy server. We presented an innovative use of SIP Tor the subscription PUBLISh is used to upload geographic information from and notification of geographic information to provide a the PUa to the sip proxy. The Sip proxy can act as a re- privacy concerned location-based service. Because this distributor of that geographic information. The SIP Proxy approach is based on SIP, it can be easily integrated into IP can then notify the geographic information to public telephony services for enabling personalization of emergency response units like a hospital, fire department or telecommunication LBS while reducing a user's privacy police station concerns in order to increase user satisfaction. LPIDF enhances sip with the required spatial location capabilities D. Implementation for supporting the personalized telecommunication services To investigate the feasibility of the proposed SIP Message Through the SIP Presence model and LPIDF, a SIP Presence flow(see Fig. 2), a prototype is developed according to the Agent(PA)can convey geographic information to pass through any SIP network. An end user can subscribe to [15]J. Rosenberg, "A Presence Event Package for the another user's lpidf in order to get the other user's Session Initiation Protocol (SIP), IETF, RFC3856 geographic location information. A LPIDF owner is able to 2004 decide the frequency and duration of information [16]J. Rosenberg, H. Schulzrinne, G. Camarillo,A availability, and control which parts of the lpidf to expose Johnston, J. Peterson,R. Sparks, M. Handley and E A lot of work still lies ahead, as our prototype still needs to Schooler. SIP: Session Initiation Protocol". IETF. RFC fined and evaluated. a methodology needs to be 3261,2002 developed to test the prototype. In order to carry out data [7JH. Sugano, S. Fujimoto, G. Klyne, A. Bateman, W collection and analysis, the LBs privacy concerns still need Carr and J. Peterson, "Presence In formation Data to be addressed through different methods. In the near Format(PIDF", IETF, RFC3863, 2004 future, we would like to provide some recommendations to LI8R. Want,A. Hopper, V Falcao and J. Gibbons,The Active Badge Location System", ACM Transactions the Geopriv working group regarding the use of SIP for Information Systems, vol. 10, pp 91-102, 1992 privacy concerned LBs [19JA.F. Westin, Privacy and Freedom, Atheneum NY Bodley head, 1967 [20JIETI SIMPI orkin Giroup, REFERENCES http://www.ietforg/htmlcharters/wg-dirhtml [1 I. Altman, The Environment and Social Behavior Privucy, Personal Space, Territory and Crowding, Monterey. CA: Brooks/ Cole. 1975 [2 P. S. Andre, "Extensible Messaging and Presence AUTHORS Protocol (XMPP: Core", IETF, RFC3920, 2004 Wilson Wu is a master student of computer Science at [3A. Beresford and F. Stajano, "Location Privacy in the University of the Western Cape. His main research Pervasive Computing", IEEE Pervasive Computing, interests are Sip presence services, location based services voL.2pp.46-55,2003 and human privacy concern 4」X.Y.Chen,Y. Chen and l.Y.Rao,“ An efticient Spatial Publish/Subscribe System for Intelligent Aleksandar Radovanovic is Lecturer in Computer Science Location Based Services", In Proceedings of the 2nd at the University of the Western Cape. His research interests International Workshop on Distributed Event-Based include the general area of computer networks and Systems, San Diego, CA, USA, pp 1-6, 2003 [5] J. Costa and H. Tang, "Application of Spatial Location protocols Information to SIP,, ACM Cluster Computing, pp 399 410.2002 William Tucker is a Senior Lecturer in Computer Science [6J. Cuellar, J. Morris, D. Mulligan, J. Peterson and J at the University of the Western Cape. He is finishing a PhD Polk, Gieopriv Requirements,IETF,RFC 3693, 2004 at the University of Cape Town on Quality of Service and [7 M. Day, J. Rosenberg and H. Sugano, A Model for multi-modal semi-synchronous IP communications Presence and Instant Messaging", IETF, RFC 2778 2000. [8 D. Hindus, S. D. Mainwaring, N. Leduc, A. E Hagstrom and 0. Bayley,"Designing Social Communication devices for the home?, a cm human Factors in Computing Systems, pp 325-332, 2001 [9 J. Hong and J. A Landay, "Support for Location: An Architecture for Privacy Sensitive Ubiquitous Computing,, In Proceedings of Mobisys 04, Boston MA,USA,pp.177-189.204. [10] A. Kanamaru and T. Yoshitsugu,"Fieldcast2 Flexible P2P architecture for presence information sharing", The Second IEEE Annual Conference on Pervasive Computing and Communications Workshops, pp 98 102、2004. [11]S. Lederer and J. Hong, Personal privacy through understanding and action: five pitfalls for designers ACM Personal and Ubiquitous Computing, vol 8, pp 440-454.2004 [12]A Niemi, "Session Initiation Protocol(SIP) Extension Tor Event state Publication".. IETF. SIP WG Internet- Dra,2004 「13]J. Peterson,“ Cornmon profile for presence(CPP)”, IETF,RFC3859,2004. [14A. B. Roach, "Session Initiation Protocol (SIP)-Specific Event Notification". IEtf rFC 3265. 2002

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