applaus: a privacy-preserving location proof updating system for location-based services zhichao zhu...
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APPLAUS: A Privacy-Preserving Location Proof Updating System for Location-based Services
Zhichao Zhu and Guohong CaoDepartment of Computer Science and Engineering
The Pennsylvania State University, University Park, PA 16802
{zzhu, gcao}@cse.psu.edu
outline
Introduction Preliminaries The Location Proof Updating
System Security Analysis and
Countermeasures Performance Evaluation Conclusions
outline
Introduction Preliminaries The Location Proof Updating
System Security Analysis and
Countermeasures Performance Evaluation Conclusions
Introduction
Location-based Services User location information Provide mobile users with a unique
style of resource and services
Target: collecting a set of location proofs for
each peer node. protecting the location privacy of peer
nodes from each other, from adversary.
outline
Introduction Preliminaries The Location Proof Updating
System Security Analysis and
Countermeasures Performance Evaluation Conclusions
Preliminaries
Pseudonym Online Certification Authority Mobile node i with a set of M
public/private key pairs . Ki
Pub serve as the pseudonyms of node i. Ki
prv enable node i to digitally sign messages.
Threat Model
Target: track the location of mobile nodes.
The adversary is internal, passive and global. Internal Passive Global
outline
Introduction Preliminaries The Location Proof Updating
System Security Analysis and
Countermeasures Performance Evaluation Conclusions
The Location Proof Updating System
Architecture Protocol Scheduling Location Proof Updates
ArchitectureProver
Witness
Server
CA
Verifier
Protocol
Protocol
(1) The prover broadcasts a location proof request through Bluetooth interface.
(2) The witness decides whether to accept the location proof request.
(3) the prover is responsible for submitting this proof to the location proof server.
Protocol
(4) An authorized verifier can query the CA for location proofs of a specific prover.
(5) The location proof server only returns hashed location rather than the real location to the CA, who then forwards to the verifier.
Scheduling Location Proof Updates
outline
Introduction Preliminaries The Location Proof Updating
System Security Analysis and
Countermeasures Performance Evaluation Conclusions
Source Location Privacy
Definition 2: source location unobservability.
Identity I, observation O ∨ O, P(I) = P(I|O), the I is called
unobservable.
Source Location Privacy
Obviously, a system satisfies source location unobservability if and only if it has the property of pseudonym unlinkability.
Source Location Privacy
outline
Introduction Preliminaries The Location Proof Updating
System Security Analysis and
Countermeasures Performance Evaluation Conclusions
Performance Evaluation
Prototype Implementation Simulation results
Prototype Implementation
Client: JAVA, Android Developer Phone, Android 1.6 OS.
Server: C++, T4300 2.1GHz 3GB RAM laptop.
Prototype Implementation
Prototype Implementation
Prototype Implementation
Simulation results 1000 mobile nodes 3km * 3km area Each node has M=10 pairs of 128-
bit public/private keys Intervalproof: the required interval
between two location proof updates.
Intervalcontact: the mean real contact interval.
Simulation results
Message overhead ratio: the ratio of dummy traffic and real proof traffic.
Simulation results
Proof delivery ratio: the percentage of location proof message that successfully uploaded to the location proof server.
Simulation results
Average delay: the time difference between the time when a location proof update is needed and when the location proof message has reach the location proof server.
outline
Introduction Preliminaries The Location Proof Updating
System Security Analysis and
Countermeasures Performance Evaluation Conclusions
Conclusions
This paper proposed a privacy-preserving location proof updating system, called APPLAUS.
It uses statistically changed pseudonyms for each device to protect source location privacy.
Extensive experimental and simulation results show that APPLAUS can provide location proofs effectively while preserving the source location privacy at the same time.
Thank you!