CN105792130A - Mass equal request-oriented k-anonymous location privacy protection method - Google Patents

Abstract

The invention discloses a mass equal request-oriented k-anonymous location privacy protection method, specifically comprising the steps of defining a user request message at a specific location; performing, by an anonymous server, anonymous processing on the user request message to generate a request message, and sending the request message to an LBS (Location-Based Service) server; returning, by the LBS server, a query result to the anonymous server; and after the anonymous server receives the query result returned by the server, performing traversing query on request messages in a current cluster, filtering respective needed real result according to the location of each user, returning the real result to each user, and finally emptying all messages of the current cluster. The method effectively reduces the computing consumption caused by repeated query while protecting the location privacy of mobile users, simultaneously reduces the communication overhead, and effectively improves the quality of service.

Description

A kind of k-anonymous location method for secret protection asked on an equal basis towards magnanimity

Technical field

The present invention relates to location Based service and security privacy technical field, particularly relate to one and on an equal basis please towards magnanimity The k-anonymous location method for secret protection asked.

Background technology

Along with wireless communication technology and the development of mobile positioning technique, it is accurately fixed that increasing mobile device possesses GPS Bit function so that location-based service (Location-Based Service is called for short LBS) is the most in fashion, becomes and carries for mobile subscriber One of service having application prospect most of confession.LBS refers to geographical position based on mobile device and other information, for mobile subscriber The information provided and entertainment service, its typical case's application includes map class application, interest point search, reward voucher or discount offer, GPS Navigation and location aware community network etc..At present, LBS has been widely used in military affairs, government's industry, business, medical treatment, has promptly rescued Help, the field such as the people's livelihood.

But, along with the development of the emerging technologies such as mobile Internet, community network, big data be widely used, LBS is giving While individual and society bring big advantages, also cause serious privacy concerns.Because user needs report when obtaining LBS Their positional information, and position data the most directly contains the privacy information of user, implies again user and generally thinks protection Other personal sensitive informations, such as home address, living habit, health status and social relations etc..Therefore, these personal informations Leakage can open the gate of abuse personal data, and the privacy of user's each side is brought serious threat.Such as, from anonymous GPS number According to middle can infer individual home address, work unit and social relations, it was predicted that go out user go over, the position of the present and the future Put, infer the whereabouts of individual；Even can utilize Indoor Location Information infer individual work role, the age, hobby (as Whether smoke) etc..Therefore, the LBS privacy to user carries out protection is a vital problem.

At present, there are many researcheres that location privacy protection correlation technique is conducted in-depth research, are broadly divided into based on opening Hairdo privacy tolerance location privacy protection technology, based on probability speculate location privacy protection technology and based on privacy information examine The location privacy protection technology of rope, the most such as k-frame technology anonymous, anonymous, privacy model based on HMM, near Search method based on privacy information etc. in adjacent inquiry.Foreign study person Reza Shokri proposes a kind of coordination mechanism and carries The privacy of high customer location.In this scenario, when mobile subscriber needs location-based service, first attempt assisting to nearby users request Helping, asking to LBS service device again if not having neighbours can share LBS information.Researcher Kenta then propose a kind of fuzzy region and Manufacture the scheme that dummy node combines, in the area that number of users is relatively more, third party's anonymous server collect abundant User, be configured to the region obscured, utilize fuzzy region to send solicited message to location server, so, location server The particular location of user cannot be known, when number of users is fewer do not reach require time, anonymous server utilizes algorithm construction Dummy node, utilizes dummy node and associated user to constitute anonymous region.

But, above-mentioned most method all relies on an anonymous server trusty, and it passes through space-time obfuscation Deng mechanism, customer location is converted, it is achieved the privacy of position.But these research methoies consider that a body position is hidden more The safety of private conversion and usefulness, do not consider safety and efficiency that large-scale group position privacy asks.

Along with the arrival of big data age, customer group may send to LBS service device in the same period substantial amounts of on an equal basis please Ask.In actual life, it is no lack of such example, such as, in the silent night evening of Wangfujing, Beijing, has substantial amounts of crowd and concentrate In region, Wangfujing, when they initiate the cuisines service near request self-position to service providers such as " popular comments " simultaneously, Anonymous server meets this magnanimity location privacy the most safely and efficiently asks on an equal basis, how to reduce and repeats to inquire about the meter brought Calculating and consume, reduce communication overhead, being effectively improved service quality just becomes the problem needing solution badly.

Summary of the invention

For the problems referred to above, the present invention provides a kind of k-anonymous location method for secret protection asked on an equal basis towards magnanimity, In conjunction with the feature of the anonymous and equal request of k-, user can formulate the privacy parameters of personalization, and these are asked by anonymous server Carry out cluster according to positional information and form anonymous territory, thus protect the location privacy of user.

The technical scheme bag of a kind of k-anonymous location method for secret protection towards the equal request of magnanimity that the present invention proposes Include following steps:

Step 1, with q=(id, loc, t, qry, d, hexa-atomic group of form k) represent be positioned at a certain ad-hoc location user please Seeking message, wherein id is that to send the user id, loc of request be the position sending request, containing (x, y) component, t sends request Time, qry is the POI of requesting query, and d is the distance of POI to the loc that anonymous server inquires, and k is that user specifies Anonymity parameter, type is integer；

After step 2, anonymous server receive above-mentioned subscription request message q, this request message is carried out anonymous process, generates Request message Q, and it is sent to LBS service device；

Query Result W is returned to anonymous server according to request message Q received by step 3, LBS service device；

After step 4, anonymous server receive the Query Result W that server is returned, according to W to each request in current cluster Message carries out traversal queries, and the legitimate reading going out each of which according to the location filtering of each user and needing is returned to each and used Family, and empty all message of current cluster.

Further, the anonymous processing procedure in step 2 comprises the following steps:

According to the qry in subscription request message q, step 1, anonymous server judge which kind of POI this subscription request message belongs to Type, adds in request queue Clu_queue [i] according to this POI type, if adding successfully, redirecting execution step 4, otherwise saying The message bunch of this POI type bright there is currently no, and continues executing with step 2；

Step 2, request queue are set up new bunch Clu_queue [i] (the most unique request message q in bunch, and Labelling its be q_i1), bunch attribute include: cover the anonymous territory center of circle O of all subscription request messages_iWith relevant radii r_i, in bunch Ultimate range MAX between each request message_iWith the message at these ultimate range two ends of connection, anonymity parameter k_max-i, in bunch, request disappears Number n of breath_iWith establishment time T_i；Wherein, k_max-iEqual to bunch in the maximum of k value of all request message, initial value is q_i1.k；T_iEqual to q_i1.t and no longer changing, the initial value of remaining parameter is: O_i(0,0), r_i=0, MAX_i=0, ni=1；

Step 3, before system time threshold value arrives, Clu_queue [i] continues waiting for next subscription request message, If there being message to arrive, returning and performing step 1；If the newest message addition bunch, if current time and a bunch establishment time T_iDifference reach system time threshold values t_out, then r is judged_i<r_l, wherein r_lLower threshold values for the anonymous territory radius of default is normal Amount, for prevent anonymous territory the least and the customer location person of being hacked that is that cause be accurately positioned after exposure；If setting up, by r_lCompose Value is to r_i, then r of being false_iConstant；No matter r_i<r_lWhether set up, all in anonymous territory, create k_max-i-n_iIndividual dummy location, now Redirect execution step 9；

If step 4 current cluster Clu_queue [i] only has request message q_i1, i.e. current message q is second message, Then need to calculate its central coordinate of circle O_i(a_i,b_i) it is the midpoint of straight line after the first place, position of two message is connected, relevant radii r_iFor This midpoint is to the distance of the arbitrary end points of straight line, MAX_iLength for this straight line；If current cluster more than one request message, then ignore This step directly performs step 5；

Step 5, position q.loc to a bunch Clu_queue [i] center of circle O of calculating subscription request message_i(ai,b_i) distance dis(q.loc,O_i), distance computing formula isJudge dis (q.loc, O_i)≤r_iWhether set up, if Be false, illustrate the position of q bunch outside, now perform step 6；If otherwise setting up, illustrate the position of q bunch in or bunch border On, now redirect execution step 8；

Each subscription request message spacing existing in step 6, calculating subscription request message q and bunch Clu_queue [i] Maximum MAX '_i=Max (dis (q_i1.loc,q.loc),dis(q_i2.loc,q.loc),,dis(q_i(n-1).loc,q.loc), dis(q_in.loc,q.loc),MAX_i), wherein MAX_iThe maximum tried to achieve before arriving for current request message；Temporarily request is disappeared Breath q is labeled as q_i(n+1), write down connection ultimate range MAX simultaneously '_iThe request message position q at two ends_iuAnd q .loc_iv1 .loc ,≤ U, v≤n+1 and u ≠ v；With q_iuAnd q .loc_iv.loc midpoint m_uv-iFor the center of circle,Justify for radius, it is judged that remaining is each Request message position is to m_uv-iDistance whether be less than or equal toIf setting up, illustrate that remaining respectively asks message at this circle In, this stylish center of circle is m_uv-i,And redirect execution step 8, otherwise perform step 7；

All of request message in step 7, traversal current cluster, finds out the position q of certain request message_iw.loc, this position will be with q_iu.loc And q_iv.loc forming minimum angle, computing formula is $Max\left(\frac{{\left(dis\right(q_{iw}.loc,q_{iu}.loc\left)\right)}^2+{\left(dis\right(q_{iw}.loc,q_{iv}.loc\left)\right)}^2}{2\left(dis\right(q_{iw}.loc,q_{iu}.loc\left)\right)\left(dis\right(q_{iw}.loc,q_{iv}.loc\left)\right)}\right);$ Then With q_iw.loc、q_iuAnd q .loc_iv.loc make circumscribed circle at 3, pass through formula: a₁=q_iv.loc.x-q_iu.loc.x, b₁= q_iv.loc.y-q_iu.loc.y, c₁=(a₁ ²+b₁ ²)/2, a₂=q_iw.loc.x-q_iu.loc.x, b₂=q_iw.loc.y- q_iu.loc.y, c₂=(a₂ ²+b₂ ²)/2, e=a₁*b₂-a₂*b₁, E.x=q_iu.loc.x+(c₁*b₂-c₂*b₁)/e, E.y= q_iu.loc.y+(a₁*c₂-a₂*c₁)/e can calculate center of circle E, radius r_EIt is then dis (q_iw.loc,E)；Judge r_E≤r_hWhether Set up, wherein r_hFor the upper threshold values constant of the anonymous territory radius of default, it is used for preventing excessive the caused LBS clothes in anonymous territory Business quality reduces；If setting up, center of circle O_i(a_i,b_i) replace with E, radius r_i=r_E, then perform step 8；If being false, with super Go out anonymous scope for being asked by refusal active user and informing that user again initiates request or again finds anonymous server；

Step 8, by message number n of current cluster_iValue adds 1, and calculates k '_max-i=Max (k_max-i, q.k), wherein k_max-i The maximum calculated in this way before adding for request message q；Judge k_max-i>n_iWhether setting up, if setting up, illustrating current Bunch Clu_queue [i] is not up to anonymity parameter requirement, now returning and performs step 3, if being false, Clu_queue [i] being described Reach anonymity parameter requirement, now continue executing with step 9；

Step 9, anonymous server create transmission message Q=(ASR, con) and are sent to LBS service device, and wherein ASR is With an O_iFor the center of circle, r_i+ d is the anonymous territory of radius, and con is the POI of requesting query ASR scope.

Beneficial effect: the method using the present invention, the equal request of magnanimity is entered by anonymous server according to position phase recency Row cluster forms the anonymous territory meeting group of subscribers privacy requirements, and then greatly reduces computing cost；Adopt during anonymity With timer operation, in case being unable to reach anonymous requirement when data volume is less for a long time and affecting service quality, and use amplification The problem that the method in anonymous region solves to be unable to reach anonymous degree of privacy.Realizing of the present invention is relatively simple, and protection is mobile to be used While the location privacy of family, effectively reduce and repeat to inquire about the calculation consumption brought, reduce communication overhead simultaneously, be effectively improved Service quality.

Accompanying drawing explanation

Fig. 1 is the anonymous flow chart of the k-anonymous location method for secret protection that the present invention asks on an equal basis towards magnanimity；

Fig. 2 is anonymous territory ASR and the current cluster anonymity territory graph of a relation of anonymous server of the present invention generation；

Fig. 3 is the mutual schematic diagram of device therefor of the present invention.

Detailed description of the invention

In conjunction with accompanying drawing and example, the present invention is further described in detail.Should be appreciated that described herein Instantiation only in order to explain the present invention, is not intended to limit the present invention.

We use hexa-atomic group of form q=, and (id, loc, t, qry, d, k) represent the request message of user, and wherein id is to send out Going out to ask the id of user, loc is the position sending request, containing (x, y) component, t is the time sending request, and qry is that request is looked into The POI ask, d is the scope of anonymous server inquiry POI to loc, and k is the anonymity parameter that user specifies, and type is integer.

Step one, transmission request

User U_idThink there is which bar near inquiry, now it is to be appreciated that user U_idPositional information, but user is not desired to again The actual position information sticked one's chin out, then user U_idIt is accomplished by sending inquiry service according to hexa-atomic group of form to anonymous server Request.In its hexa-atomic group of message of request, id fills out U_id；Loc is the positional information obtained by positioner, it is not necessary to user setup； T is user U_idSend time during request, directly obtain from client；Qry refers to inquire about neighbouring bar；D is that anonymous server is looked into Asking the scope of POI to loc, we are appointed as 1000 meters here；K represents user U_idThe anonymity parameter specified, in order to briefly describe, What k took here is less, and such as 4；User is by q=(U_id, loc, t, " bar near Cha Xun ", 1000 meters, 4) it is sent to Anonymizer Just complete request task.

Step 2, anonymous server are anonymous to message

Anonymous server according to the position in request message and inquiry content message clustered correspondence bunch in hide Nameization.

Concrete anonymous process is as follows:

After step 2.1, anonymous server receive request message q of user, sentence according to the qry in subscription request message q The POI type of this subscription request message disconnected is bar, if the request queue belonging to bar does not exists, creates new bar Request queue bunch.Assume that the request queue bunch Clu_queue [i] in bar exists, if meeting condition subsequent, then will request message q Join in request queue bunch Clu_queue [i].Assume the center of circle, anonymous territory of all subscription request messages of now bar bunch covering For O_i, its relevant radii is r_i, inter-entity ultimate range MAX in bunch_i, anonymity parameter k_max-i=4, ask the number of message in bunch n_i=3, respectively q_i1=(U_id1,loc₁,t₁, " bar near Cha Xun ", 800 meters, 4), q_i2=(U_id2,loc₂,t₂, " inquiry Near bar ", 1000 meters, 3), q_i3=(U_id3,loc₃,t₃, " bar near Cha Xun ", 1000 meters, 3).

The position q.loc of step 2.2, first computation request message arrives bunch Clu_queue [i] center of circle O_i(a_i,b_i) away from From forThen dis (q.loc, O are judged_i)≤r_iWhether set up, it is assumed that dis(q.loc,O_i)>r_i, i.e. the position of q bunch outside, during now request message q temporarily cannot be applied directly to bunch.

Each subscription request message existing in step 2.3, first calculating subscription request message q and bunch Clu_queue [i] The maximum of spacing, MAX '_i=Max (dis (q_i1.loc,q.loc),dis(q_i2.loc,q.loc),dis(q_i3.loc, q.loc),MAX_i), wherein MAX_iThe maximum tried to achieve before arriving for current request message, it is assumed that MAX '_i=dis (q_i1.loc, q.loc)；Temporarily request message q is labeled as q_i4, write down connection ultimate range MAX simultaneously '_iThe request message digit at two ends is set to q_i1And q .loc_i4.loc.With q_i1And q .loc_i4.loc midpoint m_14-iFor the center of circle,Justifying for radius, then judging please Seek message position q_i2And q .loc_i3.loc m is arrived_14-iDistance whether be less than or equal toAssume $dis(q_{i2}.loc,m_{14-i})>\frac{{{\mathrm{MAX}}^{,}}_i}{2},dis(q_{i3}.loc,m_{14-i})<\frac{{{\mathrm{MAX}}^{,}}_i}{2},$ Request message position q_i2.loc outside this circle, this Time during request message q temporarily cannot be applied directly to bunch.

Step 2.4, compare q_i2And q .loc_i3.loc with q_i1And q .loc_i4.loc form the size of angle, pass through formula $Max\left(\frac{{\left(dis\right(q_{iw}.loc,q_{iu}.loc\left)\right)}^2+{\left(dis\right(q_{iw}.loc,q_{iv}.loc\left)\right)}^2}{2\left(dis\right(q_{iw}.loc,q_{iu}.loc\left)\right)\left(dis\right(q_{iw}.loc,q_{iv}.loc\left)\right)}\right)$ Understand q_i2.loc with q_i1And q .loc_i4.loc angle is formed Cos cosine value bigger, so its angle is less, with q_i1.loc、q_i2And q .loc_i4.loc make circumscribed circle at 3, pass through formula: a₁=q_i2.loc.x-q_i1.loc.x, b₁=q_i2.loc.y-q_i1.loc.y, c₁=(a₁ ²+b₁ ²)/2, a₂=q_i4.loc.x- q_i1.loc.x, b₂=q_i4.loc.y-q_i1.loc.y, c₂=(a₂ ²+b₂ ²)/2, e=a₁*b₂-a₂*b₁, E.x=q_i1.loc.x+ (c₁*b₂-c₂*b₁)/e, E.y=q_i1.loc.y+(a₁*c₂-a₂*c₁)/e can calculate center of circle E, radius r_EIt is then dis (q_i4.loc,E)；Assume r_E≤r_h, meet the setting of system, center of circle O_i(a_i,b_i) replace with E, radius r_i=r_E, now request disappears During breath q may be added to bunch.

Step 2.5, by message number n of current cluster_iValue adds 1 and becomes 4, and calculates k '_max-i=Max (k_max-i, q.k)= Max (4,4)=4, wherein k_max-iThe maximum calculated in this way before adding for request message q；Now k_max-i=n_iIt is 4, illustrate that current cluster Clu_queue [i] has reached anonymity parameter requirement.

Step 2.6, anonymous server create transmission message Q=(ASR, con) and are sent to LBS service device, wherein ASR It is with an O_iFor the center of circle, r_i+ 1000 meters is the anonymous territory of radius, and con is the bar information in the range of requesting query ASR.

Step 3, anonymous server communicate with LBS service device

Query Result W is returned to anonymous server according to request message Q by LBS service device.

Step 4, anonymous server return legitimate reading to user after filtering

After anonymous server receives the Query Result W that LBS service device is returned, according to W to current cluster is asked message Position q_i1.loc、q_i2.loc、q_i3.loc, q.loc carry out traversal queries, leach each of which need legitimate reading return to Each user, and empty all message of current cluster.

The foregoing is only a specific embodiment of the present invention, not in order to limit the present invention, all essences in the present invention Within god and principle, any modification, equivalent substitution and improvement etc. made, should be included within the scope of the present invention.

Claims (2)

1. the k-anonymous location method for secret protection asked on an equal basis towards magnanimity, it is characterised in that comprise the following steps:

Step 1, with q=(id, loc, t, qry, d, hexa-atomic group of form k) represent be positioned at a certain ad-hoc location user request disappear Breath, wherein id is that to send the user id, loc of request be the position sending request, containing (x, y) component, when t is to send request Between, qry is the POI of requesting query, and d is the distance of POI to the loc that anonymous server inquires, and k is hideing of specifying of user Name parameter, type is integer；

After step 2, anonymous server receive above-mentioned subscription request message q, this request message is carried out anonymous process, generates request Message Q, and it is sent to LBS service device；

Query Result W is returned to anonymous server according to request message Q received by step 3, LBS service device；

After step 4, anonymous server receive the Query Result W that server is returned, according to W to each request message in current cluster Carry out traversal queries, and the legitimate reading going out each of which according to the location filtering of each user and needing return to each user, And empty all message of current cluster.

A kind of k-anonymous location method for secret protection asked on an equal basis towards magnanimity the most according to claim 1, its feature Being, the described anonymous processing procedure in step 2 comprises the following steps:

According to the qry in subscription request message q, step 1, anonymous server judge which kind of POI class this subscription request message belongs to Type, adds in request queue Clu_queue [i] according to this POI type, if adding successfully, redirecting execution step 4, otherwise illustrating The message bunch of this POI type there is currently no, and continues executing with step 2；

Step 2, request queue are set up new bunch Clu_queue [i] and (in bunch, the most uniquely asks message q, and labelling It is q_i1), bunch attribute include: cover the anonymous territory center of circle O of all subscription request messages_iWith relevant radii r_i, respectively please in bunch Seek ultimate range MAX between message_iWith the message at these ultimate range two ends of connection, anonymity parameter k_max-i, in bunch, ask message Number n_iWith establishment time T_i；Wherein, k_max-iEqual to bunch in the maximum of k value of all request message, initial value is q_i1.k；T_i Equal to q_i1.t and no longer changing, the initial value of remaining parameter is: O_i(0,0), r_i=0, MAX_i=0, n_i=1；

Step 3, before system time threshold value arrives, Clu_queue [i] continues waiting for next subscription request message, if having Message arrives then to return and performs step 1；If the newest message addition bunch, if current time and a bunch establishment time T_i's Difference reaches system time threshold values t_out, then r is judged_i<r_l, wherein r_lFor the lower threshold values constant of the anonymous territory radius of default, For prevent anonymous territory the least and the customer location person of being hacked that is that cause be accurately positioned after exposure；If setting up, by r_lIt is assigned to r_i, then r of being false_iConstant；No matter r_i<r_lWhether set up, all in anonymous territory, create k_max-i-n_iIndividual dummy location, now redirects Perform step 9；

If step 4 current cluster Clu_queue [i] only has request message q_i1, i.e. current message q is second message, then need Calculate its central coordinate of circle O_i(a_i,b_i) it is the midpoint of straight line after the first place, position of two message is connected, relevant radii r_iFor in this Point arrives the distance of the arbitrary end points of straight line, MAX_iLength for this straight line；If current cluster more than one request message, then ignore this step Rapid directly execution step 5；

Step 5, position q.loc to a bunch Clu_queue [i] center of circle O of calculating subscription request message_i(a_i,b_i) distance dis (q.loc,O_i), distance computing formula isJudge dis (q.loc, O_i)≤r_iWhether set up, if not Set up then illustrate the position of q bunch outside, now perform step 6；If otherwise setting up, illustrate the position of q bunch in or bunch border On, now redirect execution step 8；

Step 6, calculate in subscription request message q and bunch Clu_queue [i] each subscription request message spacing existing It is worth greatly MAX '_i=Max (dis (q_i1.loc,q.loc),dis(q_i2.loc, q.loc), dis (q_i(n-1).loc,q.loc),dis (q_in.loc,q.loc),MAX_i), wherein MAX_iThe maximum tried to achieve before arriving for current request message；Temporarily will request message q It is labeled as q_i(n+1), write down connection ultimate range MAX simultaneously '_iThe request message position q at two ends_iuAnd q .loc_iv.loc, 1≤u, v ≤ n+1 and u ≠ v；With q_iuAnd q .loc_iv.loc midpoint m_uv-iFor the center of circle,Justify for radius, it is judged that remaining is respectively asked Message position is to m_uv-iDistance whether be less than or equal toIf setting up, illustrate remaining respectively request message in this circle, this The stylish center of circle is m_uv-i,And redirect execution step 8, otherwise perform step 7；

All of request message in step 7, traversal current cluster, finds out the position q of certain request message_iw.loc, this position will be with q_iu.loc And q_iv.loc forming minimum angle, computing formula is $Max\left(\frac{{\left(dis\right(q_{iw}.loc,q_{iu}.loc\left)\right)}^2+{\left(dis\right(q_{iw}.loc,q_{iv}.loc\left)\right)}^2}{2\left(dis\right(q_{iw}.loc,q_{iu}.loc\left)\right)\left(dis\right(q_{iw}.loc,q_{iv}.loc\left)\right)}\right);$ Then With q_iw.loc、q_iuAnd q .loc_iv.loc make circumscribed circle at 3, pass through formula: a₁=q_iv.loc.x-q_iu.loc.x, b₁= q_iv.loc.y-q_iu.loc.y, c₁=(a₁ ²+b₁ ²)/2, a₂=q_iw.loc.x-q_iu.loc.x, b₂=q_iw.loc.y- q_iu.loc.y, c₂=(a₂ ²+b₂ ²)/2, e=a₁*b₂-a₂*b₁, E.x=q_iu.loc.x+(c₁*b₂-c₂*b₁)/e, E.y= q_iu.loc.y+(a₁*c₂-a₂*c₁)/e can calculate center of circle E, radius r_EIt is then dis (q_iw.loc,E)；Judge r_E≤r_hWhether Set up, wherein r_hFor the upper threshold values constant of the anonymous territory radius of default, it is used for preventing excessive the caused LBS clothes in anonymous territory Business quality reduces；If setting up, center of circle O_i(a_i,b_i) replace with E, radius r_i=r_E, then perform step 8；If being false, with super Go out anonymous scope for being asked by refusal active user and informing that user again initiates request or again finds anonymous server；

Step 8, the message number ni value of current cluster is added 1, and calculate k '_max-i=Max (k_max-i, q.k), wherein k_max-iFor asking Seek the maximum that message q calculates before adding in this way；Judge k_max-i>n_iWhether setting up, if setting up, current cluster being described Clu_queue [i] is not up to anonymity parameter requirement, now returning and performs step 3, if being false, Clu_queue [i] being described Through reaching anonymity parameter requirement, now continue executing with step 9；

Step 9, anonymous server create transmission message Q=(ASR, con) and are sent to LBS service device, and wherein ASR is with point O_iFor the center of circle, r_i+ d is the anonymous territory of radius, and con is the POI of requesting query ASR scope.