NOWADAYS, THE EXPANDED USE OF LBSS INVOLVES OPPORTUNITIES TO THE ADVERSARIES THREATENING THE LOCATION PRIVACY OF MOBILE USERS. SEVERAL APPROACHES HAVE BEEN PROPOSED TO TACKLE EITHER LOCATION PRIVACY, LOCATION SAFETY, AND QUERY PRIVACY INDEPENDENTLY. IN THIS PAPER, WE PRESENT A WORK IN PROGRESS, WHICH AIMS TO PROPOSE A UNIFIED FRAMEWORK TO PROTECT PRIVACY IN ALL THESE DIMENSIONS SIMULTANEOUSLY. THE DEMAND FOR QUERY-PRIVACY PROTECTION FOR MANY USERS WILL BE ADDRESSED IN BATCH.

MANY REPORTERS HAVE HIGHLIGHTED THAT LOCATION-BASED SERVICES (LBS) HAVE OPENED SEVERAL QUESTIONS CONCERNING PRIVACY. WHEN A CLIENT RELEASES HER LOCATION TO A LBS, SHE COULD PUT HERSELF IN DANGER. TO MITIGATE THIS ISSUE, RESEARCHERS HAVE PROPOSED SEVERAL LOCATION CLOAKING TECHNIQUES. HOWEVER, THESE SOLUTIONS HAVE SEVERAL DRAWBACKS. MOST OF THEM ARE BASED ON AN ANONYMIZER AND THEY DO NOT ADDRESS THE SCALABILITY ISSUES FACED BY THE SERVER WHEN A HIGH DEMAND FOR LOCATION PRIVACY PROTECTION IS REQUESTED. ALSO, THEY DO NOT CONSIDER THE POTENTIAL NEGATIVE IMPACT ON THE LBS WHEN POSTERIORI PROCESSING OF MANY LOCATIONCLOAKED QUERIES (LCQ). THIS PAPER CONSIDERS THE PROBLEMS OF EFFICIENT CONSTRUCTION OF LOCATION CLOAKING AREAS WHEN A TRUSTED ANONYMIZER NEEDS TO PROVIDE LOCATION PRIVACY PROTECTION FOR HETEROGENEOUS LBS CLIENTS AND TO LIMIT THE COST OF PROCESSING MANY LCQS AT THE LBS. OUR KEY GOAL IS TO BUILD SHARED CLOAKING REGIONS FOR LBS USERS LOCATED NEARBY EACH OTHER AND HAVING SIMILAR PRIVACY CONCERNS. WE PROPOSE SEVERAL BATCHING APPROACHES FOR BUILDING PROPER CLOAKING REGIONS. THROUGHOUT EXTENSIVE SIMULATIONS, WE WILL SHOW OUR APPROACH CAN BALANCE BOTH THE ANONYMIZER WORKLOAD AND LBS WORKLOAD.

LOCATION-BASED SERVICES (LBSS) ASSUME THAT USERS ARE WILLING TO RELEASE TRUSTWORTHY AND USEFUL DETAILS ABOUT THEIR WHEREABOUTS. HOWEVER, MANY LOCATION PRIVACY CONCERNS HAVE ARISEN. FOR LOCATION PRIVACY PROTECTION, SEVERAL ALGORITHMS BUILD A CLOAKING REGION TO HIDE A USER?S LOCATION. HOWEVER, MANY APPLICATIONS MAY NOT OPERATE ADEQUATELY ON CLOAKED LOCATIONS. FOR EXAMPLE, A TRADITIONAL DISTANCE BOUNDING PROTOCOL (DBP)?WHICH IS RUN BY TWO NODES CALLED THE PROVER AND THE VERIFIER?MAY CONCLUDE AN UNTIGHT AND USELESS DISTANCE BETWEEN THESE TWO ENTITIES. AN LBS (VERIFIER) MAY USE THIS DISTANCE AS A METRIC OF USEFULNESS AND TRUSTWORTHINESS OF THE LOCATION CLAIMED BY THE USER (PROVER). HOWEVER, WE SHOW THAT IF A TIGHT DISTANCE IS DESIRED, TRADITIONAL DBP CAN REFINE A USER?S CLOAKED LOCATION AND COMPROMISE ITS LOCATION PRIVACY. TO FIND A PROPER BALANCE, WE PROPOSE A LOCATION-PRIVACY-AWARE DBP PROTOCOL. OUR SOLUTION CONSISTS OF ADDING SOME SMALL DELAYS BEFORE SUBMITTING ANY USER?S RESPONSE. WE SHOW THAT SEVERAL ISSUES ARISE WHEN A CERTAIN DELAY IS CHOSEN, AND WE PROPOSE SOME SOLUTIONS. THE EFFECTIVENESS OF OUR TECHNIQUES IN BALANCING LOCATION REFINEMENT AND UTILITY IS DEMONSTRATED THROUGH SIMULATION.

THIS PAPER PRESENTS AN APPROACH TO TAKE ADVANTAGE OF REVIEWS WRITTEN IN SPANISH TO GENERATE ASPECT-BASED RECOMMENDATIONS. ALTHOUGH DIVERSE APPROACHES HAVE BEEN PROPOSED AND EVALUATED FOR REVIEWS WRITTEN IN ENGLISH, THERE IS A LACK OF PROPOSALS TO ACCOMPLISH THIS TASK USING REVIEWS IN SPANISH. THE PROPOSED APPROACH USES TEXT MINING TECHNIQUES AND TOOLS TO EXTRACT ITEM ASPECTS AND ESTIMATE USER PREFERENCES FOR EACH OF THEM. THE ESTIMATED PREFERENCES THEN FEED A MULTI-CRITERIA RECOMMENDER SYSTEM, CONSIDERING EACH EXTRACTED ASPECT AS A CRITERION REGARDING USER PREFERENCE. PRELIMINARY RESULTS SHOW THAT, USING ASPECTS EXTRACTED FROM REVIEWS WRITTEN IN SPANISH, IT IS POSSIBLE TO IMPROVE THE QUALITY OF RECOMMENDATIONS GENERATED WITH A TRADITIONAL ALGORITHM. DUE TO THE SIMPLICITY OF THE PROPOSED APPROACH, IT CAN BE EASILY USED BY LOCAL COMPANIES TO INCORPORATE ASPECT-BASED RECOMMENDATIONS.

THIS PAPER PRESENTS A SUBSCRIPTION-BASED OVERLAY NETWORK THAT SUPPORTS FILE PARALLEL DOWNLOADING FOR CLOUD COLLABORATION. FIRST, OUR SYSTEM LETS USERS TO REGISTER TO A CENTRAL SERVER AND ALLOWS THIS SERVER TO INCREMENTALLY BUILD A TOPOLOGY GRAPH CONTAINING THE NETWORK CONNECTIONS AMONG THE SUBSCRIBERS. WITH THIS TOPOLOGY GRAPH IN PLACE, WE PLAN TO ADDRESS THE CHALLENGES OF MINIMIZING NETWORK TRAFFIC AND CHOOSING THE BEST SET OF NODES STORING A CHOSEN FILE FOR PARALLEL DOWNLOADING. WHEN A SUBSCRIBER WANTS TO ACCESS A CHOSEN FILE STORED IN THE CLOUD, OUR SYSTEM OBTAINS FOR HER A LIST OF NODES HAVING THIS FILE. NODES IN THIS LIST, ARE SORTED CONSIDERING BOTH THEIR NETWORK DISTANCE TO THE SUBSCRIBER AND THEIR WORKLOADS. SECOND, SELECTING THOSE TOP NODES, A BANDWIDTH-AWARE PARALLEL DOWNLOADING TECHNIQUE IS EXECUTED. FINALLY, OUR PROPOSED SYSTEM ALSO FEATURES LEVERAGING IDLING NODES FOR FILE DOWNLOADING. MORE SPECIFICALLY, THE SUBSCRIBERS WHO ARE ON-LINE BUT NOT PARTICIPATING IN DOWNLOADING ARE RECRUITED TO REDUCE BOTH NETWORK TRAFFIC AND AVERAGE LATENCY.

THIS PAPER FOCUSES ON ADOPTING CYBERSECURITY PROCEDURES IN CHILEAN MANUFACTURING COMPANIES IN THE CONTEXT OF THE FOURTH INDUSTRIAL REVOLUTION?S DATA-DRIVEN DEMANDS, WHICH HAVE EXPOSED VULNERABILITIES IN CYBERSECURITY. THIS ANALYSIS IS BASED ON DATA FROM THE FIFTH LONGITUDINAL SURVEY OF COMPANIES - ELE 5 - CONDUCTED BY THE NATIONAL INSTITUTE OF STATISTICS. USING THE TOE ADOPTION MODEL, WE EMPLOY BINARY AND ORDERED LOGIT AND PROBIT MODELS WITH DATA FROM 574 COMPANIES AND 17 EXPLANATORY VARIABLES. THE OBJECTIVE IS TO GAIN INSIGHT INTO THE FACTORS INFLUENCING THE ADOPTION OF CYBERSECURITY PROCESSES, COMPLEMENTING THE EXISTING LITERATURE, WHICH OFTEN FOCUSES ON DEVELOPING SPECIFIC TECHNOLOGIES OR CONDUCTING COMPREHENSIVE ANALYSES OF DIGITAL TRANSFORMATION. THE STUDY HIGHLIGHTS THE SIGNIFICANCE OF COMPANY SIZE IN EXPLAINING THE ADOPTION OF CYBERSECURITY PROCEDURES AND REVEALS THE RELEVANCE OF EXPLANATORY VARIABLES AS THE DEPTH OF ADOPTION INCREASES. THE FINDINGS UNDERSCORE THE NEED FOR PUBLIC POLICIES THAT FACILITATE THE IMPLEMENTATION OF EXISTING REGULATIONS, SUCH AS ISO 27.001, PARTICULARLY FOR SMALL COMPANIES. ADDITIONALLY, THE STUDY EMPHASIZES THE IMPORTANCE OF FOSTERING A

LOCATION-BASED SERVICES (LBSS) HAVE BECOME A PROFITABLE MARKET BECAUSE THEY OFFER REAL-TIME AND LOCAL INFORMATION TO THEIR USERS. ALTHOUGH SEVERAL BENEFITS ARE OBTAINED FROM THE USAGE OF LBSS, THEY HAVE OPENED UP MANY PRIVACY AND SAFETY CHALLENGES BECAUSE A USER NEEDS TO RELEASE HIS/HER LOCATION. TO TACKLE THESE CHALLENGES, MANY LOCATION-CLOAKING TECHNIQUES HAVE BEEN PROPOSED. EVEN THOUGH THESE SOLUTIONS ARE EFFECTIVE IN PROTECTING EITHER LOCATION PRIVACY OR LOCATION SAFETY, THEY DO NOT PROVIDE UNIFIED PROTECTION. FURTHERMORE, MOST OF THEM DO NOT ADDRESS THE POTENTIAL BOTTLENECK IN THE ANONYMITY SERVER AS A HIGH DEMAND OF LOCATION AND SAFETY PROTECTION IS REQUESTED. FINALLY, THEY DO NOT TAKE INTO ACCOUNT THE POTENTIAL IMPACT OF PROCESSING A LARGE AMOUNT OF LOCATION-CLOAKED QUERIES. THIS PAPER DEALS WITH THE EFFICIENT CONSTRUCTION OF LOCATION-CLOAKING AREAS FOR MANY USERS, WHO HAVE BOTH PRIVACY AND SAFETY REQUIREMENTS. TO ACHIEVE THIS GOAL, THE CONSTRUCTION OF LOCATION-CLOAKING AREAS IS CARRIED OUT IN BATCHES. THE LBSS? BATCH PROCESSING TAKES ADVANTAGE OF USERS WHO ARE CLOSE TO EACH OTHER AND WHO HAVE SIMILAR REQUIREMENTS. TWO BATCHING TECHNIQUES TO BUILD CLOAKING REGIONS ARE ANALYZED USING SIMULATIONS. EMPIRICAL RESULTS SHOW OUR TECHNIQUES ARE ABLE TO BALANCE THE ANONYMIZER WORKLOAD, QUALITY OF LOCATION PRIVACY AND SAFETY PROTECTION, AND LBS WORKLOAD.

SOCIAL NETWORKS SUCH AS TWITTER PROVIDE THOUSANDS OF TERABYTES PER DAY, WHICH CAN BE EXPLOITED TO FIND RELEVANT INFORMATION. THIS RELEVANT INFORMATION IS USED TO PROMOTE MARKETING STRATEGIES, ANALYZE CURRENT POLITICAL ISSUES, AND TRACK MARKET TRENDS, TO NAME A FEW EXAMPLES. ONE INSTANCE OF RELEVANT INFORMATION IS FINDING CYCLIC BEHAVIOR PATTERNS (I.E., PATTERNS THAT FREQUENTLY REPEAT THEMSELVES OVER TIME) IN THE POPULATION. BECAUSE TRENDING TOPICS ON TWITTER CHANGE RAPIDLY, EFFICIENT ALGORITHMS ARE REQUIRED, ESPECIALLY WHEN CONSIDERING LOCATION AND TIME (I.E., THE SPECIFIC LOCATION AND TIME) DURING BROADCASTS. THIS ARTICLE PRESENTS AN EFFICIENT ALGORITHM BASED ON ASSOCIATION RULES TO FIND CYCLICAL PATTERNS ON TWITTER, CONSIDERING THE INHERENT SPATIO-TEMPORAL ATTRIBUTES OF DATA. USING A HASH TABLE ENHANCES THE EFFICIENCY OF THIS ALGORITHM, CALLED HASHCYCLE. NOTABLY, HASHCYCLE DOES NOT USE MINIMUM SUPPORT AND CAN DETECT PATTERNS IN A SINGLE RUN OVER A SEQUENCE. THE PROCESSING TIMES OF HASHCYCLE WERE COMPARED TO THE APRIORI (WHICH IS A WELL-KNOWN AND WIDELY USED ON DIVERSE PLATFORMS) AND PROJECTION-BASED PARTIAL PERIODIC PATTERNS (PPA) ALGORITHMS (WHICH IS ONE OF THE MOST EFFICIENT ALGORITHMS IN TERMS OF PROCESSING TIMES). EMPIRICAL RESULTS FROM TWO SPATIO-TEMPORAL DATABASES (A SYNTHETIC DATA SET AND ONE BASED ON TWITTER) SHOW THAT HASHCYCLE HAS MORE EFFICIENT PROCESSING TIMES THAN TWO STATE-OF-THE-ART ALGORITHMS: APRIORI AND PPA.

WIRELESS TECHNOLOGIES ARE OPENING MANY POSSIBILITIES FOR MONITORING AND CONTROL APPLICATIONS, DRIVING MUCH RESEARCH EFFORTS IN THE LAST YEARS. REGARDING THE MAY CHALLENGING ISSUES RELATED TO INDUSTRIAL WIRELESS SENSOR NETWORKS (IWSN), EFFICIENT NODES DEPLOYMENT IS A MAJOR CONCERN SINCE IT CAN DIRECTLY IMPACT THE NETWORK BEHAVIOR. IN MANY CASES, IWSN INCLUDE PARTICULAR KIND OF NODES IN WHICH THE SENSOR UNIT AND THE WIRELESS TRANSMISSION UNITS ARE NOT LOCATED IN THE SAME PLACE. IN THIS PAPER, WE PROVIDE A SOLUTION TO THIS PROBLEM THROUGH A GENETIC ALGORITHM (GA), CAPABLE OF GIVE A SET OF POSITIONS FOR THE SET WIRELESS TRANSMITTERS, SUCH THAT EACH NODE CAN REACH A GATEWAY UNIT AND IT SATISFIES A MAXIMUM DISTANCE TO ITS RESPECTIVE SENSOR UNIT WHICH IS GIVEN BY THE MAXIMUM LENGTH OF THE CABLE CONNECTING THE ELEMENTS. RESULTS SHOW THAT OUR GA FINDS OPTIMAL SOLUTIONS FOR THE SIMPLIFIED CONSIDERED CASE IN VERY SHORT EXECUTION TIMES.

WEB SEARCH ENGINES PROCESS SEVERAL MILLIONS OF QUERIES PER SECOND OVER SEVERAL BILLIONS OF DOCUMENTS. WITHOUT ANY OPTIMIZATION, THIS PROCESS CAN BE VERY EXPENSIVE IN TERMS OF PROCESSING TIMES. IN THIS REGARD, APPROPRIATE USE OF COMPUTING POWER IS ESSENTIAL. ONE WAY TO TACKLE THIS PROBLEM IS THROUGH THE USE OF CACHING MECHANISMS. KEEP IN MIND, MOST RESEARCH BASED ON CACHING MECHANISMS USES REPETITIVE QUERIES-IT MEANS QUERIES SYNTACTICALLY EQUALS-TO CONFORM CACHES. FURTHERMORE, THE UNIVERSE OF REPETITIVE QUERIES IS SMALL IN COMPARISON WITH A SET OF SIMILAR SEMANTICALLY QUERIES. THIS PAPER PRESENTS A DYNAMIC CACHE THAT RELIES ON AN ONLINE ALGORITHM, WHICH PERFORMS A SEMANTIC MATCH BETWEEN THE USER?S QUERY AND QUERIES STORED IN THE CACHE. BROADLY SPEAKING, THE ALGORITHM EMPLOYS A PRIORITY QUEUE, WHERE POPULAR QUERIES ARE STORED ALONG WITH THEIR RELEVANT DOCUMENTS. EMPIRICAL RESULTS SHOW THAT OUR PROPOSED APPROACH IMPROVES THE RESPONSE TIMES AND PRECISION. MOREOVER, THE USE OF SEMANTICALLY RELATED KEYWORDS PROVES TO BE A KEY CONTRIBUTION THAT HAD BEEN OVERLOOKED IN PREVIOUS RESEARCH.

NOWADAYS, PEOPLE CAN ACCESS A WIDE RANGE OF APPLICATIONS AND SERVICES FOR MOBILE DEVICE USERS. AMONG THEM, LOCATION-BASED SERVICES (LBS), WHERE THE APPLICATION NEEDS THE USER?S POSITION TO PROVIDE THE SERVICE. SOME EXAMPLES OF THESE APPLICATIONS ARE UBER AND WAZE. NEVERTHELESS, THE REPETITIVE USE OF AN LBS CAN REVEAL CONFIDENTIAL USER INFORMATION; THUS, BEHAVIOR PATTERNS?SUCH AS DAILY ROUTES?COULD BE DEDUCED BY SOME DISHONEST LBS. FURTHERMORE, A QUERY?S KEYWORDS COULD PROVIDE INFORMATION ABOUT A USER?S HEALTH STATUS OR FUTURE POSITION WHEN IT INQUIRES ABOUT HOSPITALS OR HOTELS. THEREFORE, AN ADVERSARY CAN USE THIS INFORMATION FOR UNETHICAL PURPOSES, AND USERS NEED MECHANISMS THAT PROTECT THEIR PRIVACY. AT PRESENT, SEVERAL APPROACHES SEPARATELY TACKLE LOCATION PRIVACY, LOCATION SECURITY, AND QUERY PRIVACY. TO THE BEST OF OUR KNOWLEDGE, NO PREVIOUS WORK DEALS WITH ALL THESE MENTIONED ASPECTS SIMULTANEOUSLY ESPECIALLY WHEN USERS DEMAND CONTINUOUS PROTECTION WHEN MOVING AND ACCESSING AN LBS. THIS PAPER PROPOSES TWO BATCH TECHNIQUES TO PROVIDE LOCATION PRIVACY, LOCATION SAFETY, AND QUERY PRIVACY IN AN ENVIRONMENT THAT CONSIDERS A CONTINUOUS LBS. THESE TECHNIQUES APPLY -DIVERSITY (QUERY PRIVACY) IN A CONTEXT THAT CONTEMPLATES QUERY SEMANTICS, AS WELL AS A DIVERSE SET OF USERS? PATHS. EXTENSIVE EXPERIMENTATION SHOWS THAT BOTH TECHNIQUES ARE COST-EFFECTIVE AND SCALABLE SOLUTIONS THAT OFFER UNIFIED LOCATION PRIVACY, QUERY PRIVACY, AND LOCATION SAFETY PROTECTION FOR MANY MOBILE USERS.

THE USE OF SENSING TECHNOLOGIES IN INDUSTRIAL NVIRONMENTS HAS OPENED MANY POSSIBILITIES FOR MONITORING AND CONTROL APPLICATIONS, DRIVING MUCH RESEARCH EFFORTS IN THE LAST YEARS. AMONG THE CHALLENGING ISSUES RELATED TO INDUSTRIAL WIRELESS SENSOR NETWORKS, EFFICIENT NODES DEPLOYMENT IS A MAJOR CONCERN SINCE IT CAN DIRECTLY IMPACT THE WAY SENSORS OPERATE, WHICH HAS DEMANDED PROPER SOLUTIONS. WHEN SENSING UNITS AND TRANSCEIVER HARDWARE ARE NOT LOCATED IN THE SAME BOARD, AS IT CAN HAPPEN IN INDUSTRIAL ENVIRONMENTS, OPTIMAL DEPLOYMENT ALGORITHMS HAVE TO DEAL WITH ADDITIONAL PARAMETERS, SUCH AS THE SIZE OF THE CABLE CONNECTING THOSE ELEMENTS AND IDEAL POSITIONING FOR BOTH SENSING AND COMMUNICATION. IN SUCH WAY, THIS PAPER TACKLES THE PROBLEM OF NODE DEPLOYMENT IN INDUSTRIAL WIRELESS SENSOR NETWORKS, DISCUSSING PRACTICAL SCENARIOS AND CHALLENGING ISSUES. MOREOVER, A LOW COMPLEXITY EXAMPLE IS GIVEN IN ORDER TO ILLUSTRATE THE DIFFERENT ELEMENTS REQUIRED.

UNTRUSTWORTHY LBS CAN COMPROMISE THEIR CLIENTS BY RELEASING THEIR LOCATION AND SENSITIVE QUERY ATTRIBUTES WITHOUT PERMISSION. THE TRADITIONAL APPROACH TO PROTECT USERS? PRIVACY IS BUILDING A SET OF DUMMY QUERIES THAT AIM TO PROTECT LOCATION USING K-ANONYMITY AND THE QUERY ATTRIBUTES, USING L-DIVERSITY. HERE, PRIVACY IS ACHIEVED AT THE EXPENSE OF THE LBS SERVER SINCE IT CAN QUICKLY BECOME A BOTTLENECK WHEN THE NUMBER OF LBS REQUESTS IS INCREASED. THIS WORK PROPOSES THAT THE LBS SERVER PERIODICALLY BROADCASTS SELECTED PUBLIC DATA INTO A PUBLIC AIR CHANNEL. MEANWHILE, USERS INTEND TO SOLVE THEIR QUERIES BY LISTENING TO THIS CHANNEL. IN THIS WAY, PRIVACY IS PRESERVED WITHOUT INCREASING THE SERVER WORKLOAD. HOWEVER, WHEN A USER DOES NOT FIND THE NEEDED DATA IN THE AIR, IT SUBMITS A LOCATION CLOAKED QUERY (LCQ) TO THE LBS SERVER. WE PROPOSE SOME APPROACHES ON HOW TO ADJUST A PERIODIC DATA BROADCASTING PROGRAM THAT BALANCES THE RESPONSE TIME INCURRED IN LOCATING DATA ON THE AIR CHANNEL AND THE LOSS OF PRIVACY WHEN USERS DIRECTLY CONTACT THE LBS. THUS, OUR IDEA IS THAT THE LBS SERVER TREATS THE WIRELESS CHANNEL AS A CACHE MEMORY AND KEEPS BROADCASTING THE MOST RELEVANT DATA PERIODICALLY.

WE PLAN TO ADDRESS THE PROBLEM OF PROCESSING LOCATION-BASED QUERIES (LBQ) IN A MANET FOR PRESERVING QUERY PRIVACY AS MUCH AS POSSIBLE. OUR IDEA IS THAT MOBILE USERS WILL FIRST ASK THEMSELVES FOR SOLVING A QUERY BEFORE ANY USER DECIDES TO SUBMIT ITS QUERY TO AN UNTRUSTED LBS. OUR FIRST GOAL IS TO DEFINE A COLLABORATIVE CACHING STRATEGY TO BE RUN BY THE MOBILE USERS THEMSELVES THAT EXPLOIT THE GEOGRAPHIC AND SEMANTIC SIMILARITIES AMONG THE LBQS TO PERFORM EFFICIENT PROCESSING OF LCQS. OUR SECOND GOAL TO PROTECT A USER?S QUERY PRIVACY WHEN ANY USER SUBMITS AN LBQ TO THE LBS; WE ARE PLANNING TO DEVELOP A DISTRIBUTED ALGORITHM TO PROVIDE L-DIVERSITY ONLY WHEN THIS PROTECTION IS USEFUL. EXISTING CACHING TECHNIQUES FOR MANET DO NOT EXPLOIT SEMANTIC AND GEOGRAPHIC SIMILARITIES AMONG THE LBQS, AND THEY ASSUME MOBILE USERS HAVE ACCESS TO SOME STORAGE INFRASTRUCTURE TO MAINTAIN GLOBAL INFORMATION TO COMPUTE L-DIVERSITY.