Trajectory Privacy Protection Research Articles

Trajectory privacy protection method with smart contract-based query exchange in the Social Internet of Vehicles

Query exchange in the Social Internet of Vehicles (SIoV) can protect users’ trajectory information. However, this method lacks an appropriate incentive mechanism, which leads to cooperative users refusing to participate in query exchange. In order to provide cooperative users with incentives to participate in query exchange, this paper proposes a smart contract-based query exchange (SC-QE) trajectory privacy protection method. By creating a many-to-many smart contract, the method encourages the cooperative users to bid to the requesting users. Subsequently, in order to select a Best Similarity Deviation User (BSDU) for the requesting user to perform query exchange, the users in the smart contract are modeled as a weighted bipartite graph, and the matching between the requesting users and BSDUs is realized by means of a weighted bipartite graph best matching algorithm. Following successful verification of the query exchange transaction in the smart contract, the base station distributes rewards to the BSDU and uploads the query exchange transaction to the consortium blockchain. Experimental results show that compared with the deviation-based query exchange (DQE) method, the proposed method reduces the user processing time by 12% while increasing the continuous anonymous success rate by 29%. Therefore, the proposed method can reduce the service query time and improve the level of trajectory privacy protection.

A three-way trajectory privacy-preserving model based on multi-feature fusion

The prevalent method in trajectory privacy protection through publishing k-1 similar trajectories alongside a target trajectory, often relies on a single feature, which can compromise the balance between privacy, data utility, and processing efficiency. Addressing this, our study introduces a nuanced three-way decision model that integrates multiple trajectory features: staying areas, average velocity, and distance. This model begins by filtering candidate trajectories through staying areas and average velocity. Subsequently, it employs a three-way decision-making process based on a novel dynamic trajectory warping (DTrW) distance metric, which obviates the need for trajectory pre-alignment and mitigates information loss. This process classifies trajectories into accepted, rejected, or pending categories, with the final set compiled through a combined metric of average speed and staying areas. Comparative experiments on a classic real trajectory dataset validate the model’s superiority, demonstrating enhanced privacy protection, improved data utility, and increased efficiency over single-feature-based approaches and other k-anonymity models.

A Privacy-Preserving Trajectory Publishing Method Based on Multi-Dimensional Sub-Trajectory Similarities.

With the popularity of location services and the widespread use of trajectory data, trajectory privacy protection has become a popular research area. k-anonymity technology is a common method for achieving privacy-preserved trajectory publishing. When constructing virtual trajectories, most existing trajectory k-anonymity methods just consider point similarity, which results in a large dummy trajectory space. Suppose there are n similar point sets, each consisting of m points. The size of the space is then mn. Furthermore, to choose suitable k- 1 dummy trajectories for a given real trajectory, these methods need to evaluate the similarity between each trajectory in the space and the real trajectory, leading to a large performance overhead. To address these challenges, this paper proposes a k-anonymity trajectory privacy protection method based on the similarity of sub-trajectories. This method not only considers the multidimensional similarity of points, but also synthetically considers the area between the historic sub-trajectories and the real sub-trajectories to more fully describe the similarity between sub-trajectories. By quantifying the area enclosed by sub-trajectories, we can more accurately capture the spatial relationship between trajectories. Finally, our approach generates k-1 dummy trajectories that are indistinguishable from real trajectories, effectively achieving k-anonymity for a given trajectory. Furthermore, our proposed method utilizes real historic sub-trajectories to generate dummy trajectories, making them more authentic and providing better privacy protection for real trajectories. In comparison to other frequently employed trajectory privacy protection methods, our method has a better privacy protection effect, higher data quality, and better performance.

A Triple Real-Time Trajectory Privacy Protection Mechanism Based on Edge Computing and Blockchain in Mobile Crowdsourcing

With the rapid development of the Internet of Things (IoT) and the rapid popularization of 5G networks, the data that needs to be processed in Mobile Crowdsourcing (MCS) system is increasing every day. Traditional cloud computing can no longer meet the needs of crowdsourcing for real-time data and processing efficiency, thus, edge computing was born. Edge computing can be calculated at the edge of network so that greatly improve the efficiency and real-time performance of data processing. In addition, most of the existing privacy protection technologies are based on the trusted third parties. Therefore, in view of the semi-trustworthiness of edge servers and the transparency of blockchain, this paper proposes a triple real-time trajectory privacy protection mechanism (T-LGEB) based on edge computing and blockchain. Through combining the localized differential privacy and multiple probability extension mechanism, the T-LGEB mechanism is proposed to send the requests and data to the edge server in this paper. Then, through the spatio-temporal dynamic pseudonym mechanism proposed in the paper, the entire trajectory of task participants is divided into multiple unrelated trajectory segments with different pseudonymous identities in order to protect the trajectory privacy of task participants while ensuring high data availability and real-time data. Through a large number of experiments and comparative analysis on multiple real data sets, the proposed T-LGEB has extremely high privacy protection capabilities and data availability, and the resource consumption caused is relatively low.

Data Dissemination With Trajectory Privacy Protection for 6G-Oriented Vehicular Networks

Data dissemination of vehicles is critical for vehicular networks because of the extensive impact of traffic information. The existing works for data dissemination in vehicular networks mainly use data scheduling algorithms to transmit data among vehicles. However, it is challenging to meet the ultrareliable and low-latency requirements of data transmission among vehicular networks due to the intrinsic movement characteristic of vehicles. To promote the data dissemination of vehicular networks, a data dissemination algorithm with trajectory privacy protection is proposed in this article, which leverages the cooperative distribution of key tasks and distance deviation. Specifically, the key tasks are disseminated to vehicles first, and the trajectory privacy protection scheme is further developed to guarantee the security of data transmission by the exploration of distance deviation and pseudonym entropy. Simulation results indicate that the proposed adaptive data dissemination algorithm is approximately 60%, 69%, and 50% better than the state-of-the-art scheduling algorithms in terms of connectivity degree, transmission delay, and average distance deviation for the vehicular network.

Trajectory Privacy Protection Based on Sensitive Stay Area Replacement in Publishing

In data opening and sharing, a trajectory privacy protection based on sensitive stay area replacement (SSAR) is proposed in order to improve the availability of protected trajectory while maintaining the same security. Firstly, the stay areas are extracted by analyzing the movement characteristics. Secondly, the sensitive stay areas are obtained according to the user-defined sensitive semantic positions. Then, the sensitive areas are constructed according to the user's privacy requirement needs to randomly select the substitution. Finally, part of the sampling positions in the sensitive area are reset. The parameter selection experiment and the comparison experiment with other schemes show that the trajectory similarity is improved by more than 35% in SSAR. That is to say, SSAR can greatly improve the availability of protected trajectory on the basis of ensuring the safety degree.

Real-time trajectory privacy protection based on improved differential privacy method and deep learning model

Accurate and real-time trajectory data publishing plays an important role in providing users with the latest traffic and road condition information to help in rationally planning travel time and routes. However, the improper publishing of location information and reverse analysis and reasoning can easily leak users’ personal information, which may threaten users’ privacy and lives. Owing to the inclusion of differential privacy model noise, privacy protection introduces inaccuracies in data publishing and validity. To improve the accuracy and usability of published data, we propose a data publishing method based on deep learning and differential privacy models for securing spatiotemporal trajectory data publishing. The method divides the trajectory data into two-dimensional grid regions, counts the density of trajectories at grids, performs a top-down recursive division of regions, and formulates rules for privacy budget allocation from multiple perspectives as recurrence depth increases. Furthermore, the method integrates spatiotemporal sequence data according to temporal order. Subsequently, it extracts temporal and spatial features of the data by the temporal graph convolutional network model for budget matrix prediction, adds Laplace noise to the regions, and evaluates the effect of differential privacy protection with the original data to protect trajectory data privacy. Experiments demonstrate that under the premise of satisfying ε-difference privacy, the query error and Jensen–Shannon divergence are smaller, the Kendall coefficient is more consistent, and the upper and lower limit values are more stable. Hence, the top-down division method achieves better results than those of the two traditional region division methods of the uniform grid and adaptive grid. The proposed method can be used to allocate the privacy budget more reasonably and achieve privacy protection of trajectories, which can be applied to a large amount of spatiotemporal trajectory data.

Novel trajectory privacy protection method against prediction attacks

When the public uses Location-based Services (LBSs), their location information is constantly exposed. Owing to the spatiotemporal correlation of trajectories, it is easy for attackers to use historical trajectories and background knowledge to predict future locations of target users. We refer to this type of inference attack as a trajectory prediction attack. To address such potential but threatening attacks in a continuous location query, we propose a novel trajectory privacy protection method. The proposed algorithm aims to generate an indistinguishable perturbed location that is robust to the prediction attack, wherein the user’s real location can be replaced by a perturbed location when submitted to an untrusted server. First, a hidden Markov model-based trajectory prediction mechanism is proposed to simulate predictive attacks and compute the predictability of positions before the trajectory is released. Second, the w sliding window mechanism is designed to dynamically adjust the privacy protection degree of each location point in the trajectory according to the predictability of the location and privacy needs of users. Finally, we propose a bounded noise-adding algorithm based on the Laplace mechanism to improve the usability of data. In our experiments, mutual information, trajectory root-mean-square error, query error, and root-mean-square predictability were used as evaluation criteria, and the performance of the proposed method was comprehensively evaluated. The results show that our algorithm can reduce the trajectory predictability to 0.21 without reducing data availability, which is effective against prediction attacks.

Protecting Location Privacy of Users Based on Trajectory Obfuscation in Mobile Crowdsensing

In mobile crowdsensing activities, it is usually necessary for participants to upload sensing data and related locations. The existing location privacy-preserving mechanisms cannot well protect a user's trajectory privacy because attackers can mine the user's trajectory features through data analysis techniques. Aiming at the trajectory privacy protection problem, this article proposes a differential location privacy-preserving mechanism based on trajectory obfuscation (LPMT). LPMT first extracts the stay points as the features of a trajectory based on the sliding window algorithm, and then obfuscates each stay point to a target obfuscation subregion through the exponential mechanism, and finally performs the Laplace sampling in the target obfuscation subregion to obtain the obfuscated GPS points. Compared with the baseline mechanisms, LPMT can reduce data quality loss by more than 20% while providing the same level of obfuscation quality, which indicates that LPMT has the advantages of strong security and high quality of service.

Successive Trajectory Privacy Protection with Semantics Prediction Differential Privacy.

The publication of trajectory data provides critical information for various location-based services, and it is critical to publish trajectory data safely while ensuring its availability. Differential privacy is a promising privacy protection technology for publishing trajectory data securely. Most of the existing trajectory privacy protection schemes do not take into account the user’s preference for location and the influence of semantic location. Besides, differential privacy for trajectory protection still has the problem of balance between the privacy budget and service quality. In this paper, a semantics- and prediction-based differential privacy protection scheme for trajectory data is proposed. Firstly, trajectory data are transformed into a prefix tree structure to ensure that they satisfy differential privacy. Secondly, considering the influence of semantic location on trajectory, semantic sensitivity combined with location check-in frequency is used to calculate the sensitivity of each position in the trajectory. The privacy level of the position is classified by setting thresholds. Moreover, the corresponding privacy budget is allocated according to the location privacy level. Finally, a Markov chain is used to predict the attack probability of each position in the trajectory. On this basis, the allocation of the privacy budget is further adjusted and its utilization rate is improved. Thus, the problem of the balance between the privacy budget and service quality is solved. Experimental results show that the proposed scheme is able to ensure data availability while protecting data privacy.

The dummy‐based trajectory privacy protection method to resist correlation attacks in Internet of Vehicles

SummaryExisting dummy‐based trajectory privacy protection schemes do not take into account the correlation of multiple locations and whether the generated trajectory based on dummies matches the user's movement mode, which enables the adversary to identify some dummies. Aiming at this problem, to ensure that the generated trajectories match the movement modes of users, historical query trajectories of users are selected. In this way, the generated dummies on the selected historical query trajectories are based on the location relationship of adjacent time and the background information constraint of the dummy, namely, they should meet the time reachability, the similarity of historical query probability and the maximum in‐degree. Security analysis shows that the proposed scheme effectively perturbs the spatiotemporal correlation between the real location and dummies. Furthermore, the proposed scheme is compared with the existing schemes in terms of single‐point location exposure risk and trajectory exposure risk, and the experimental results indicate that the proposal has significant improvement in location privacy protection of the user.

Cloud Edge-Client Collaborative Trajectory Privacy Protection System and Technology

Location-based service (LBS), with its personalized, real time, and mobile features, is one of the more popular mobile applications (apps) in the world today. However, under the centralized LBS architecture, the high dimensional trajectory data collected from LBS users are directly exposed to the central server, which entails serious privacy risks. Although existing privacy protection technologies can protect the private user trajectories to a certain extent, they often ignore the reasonable data requirements of LBS providers (e.g., data required to maintain or improve services). Focusing on the weaknesses of centralized LBS and the shortcomings of existing solutions, this article proposes a cloud edge-client collaborative trajectory privacy protection system. The system migrates LBS from the cloud to the network edge and balances privacy and utility-including service utility and data utility-with anonymous authentication, dummy location, and privacy risk evaluation mechanisms. The theoretical analysis and simulation results show that the system can effectively protect trajectory privacy under the premise of high availability of services and data, which is a significant improvement over the current LBS system.

Utility-aware and Privacy-preserving Trajectory Synthesis Model that Resists Social Relationship Privacy Attacks

For academic research and business intelligence, trajectory data has been widely collected and analyzed. Releasing trajectory data to a third party may lead to serious privacy leakage, which has spawned considerable researches on trajectory privacy protection technology. However, existing work suffers from several shortcomings. They either focus on point-based location privacy, ignoring the spatio-temporal correlations among locations within a trajectory, or they protect the privacy of each user separately without considering privacy leakage of the social relationship between trajectories of different users. Besides, they fail to balance privacy protection and data utility. Motivated by these limitations, in this article, we propose S 3 T -Trajectory, which is a utility-aware and privacy-preserving trajectory synthesis model that Resists social relationship privacy attacks. Specifically, we first develop a time-dependent Markov chain based on an adaptive spatio-temporal discrete grid to efficiently and accurately capture human mobility behavior. Then, we propose three mobility feature metrics from spatio-temporal, semantic, and social dimensions. On the basis of the metrics, we construct a bi-level optimization problem to accomplish the utility-aware and privacy-preserving trajectory synthesizing. The upper-level objective guarantees data utility and the lower-level optimization problems (or upper-level constraints) provides two-layer privacy protection for S 3 T -Trajectory, i.e., resisting location inference attacks and social relationship privacy attacks. We conduct extensive experiments on large-scale real-world datasets loc-Gowalla and loc-Brightkite. The experimental results demonstrate the effectiveness and robustness of S 3 T Trajectory. Compared with the baseline models, S 3 T Trajectory achieves between 7.8% and 23.8% performance improvement in resisting social relationship privacy attacks and achieves at least 5.19% improvement regarding data utility.

Local Trajectory Privacy Protection in 5G Enabled Industrial Intelligent Logistics

The value of trajectory data lies mainly in the spatio-temporal correlation. However, the existing privacy protection methods ignore the spatio-temporal correlation of trajectory data, resulting in a large error in trajectory proportion estimation and Top-K classification. For the privacy of truck trajectory in intelligent logistics, the location and trajectory data perturbation method based on quadtree indexing is proposed, which leverages location generalization and local differential privacy techniques. Our proposed algorithms are suitable for datasets with a large sample space and can protect the trajectory privacy of truck drivers while preserving the strong correlation between adjacent spatio-temporal nodes in the trajectory. The results of simulation on a real trajectory dataset show that the proposed methods not only meet the trajectory privacy requirements of users but also have a good performance in trajectory proportion estimation and Top-K classification.

Intelligent Privacy Protection of End User in Long Distance Education

Long distance education is an important part during the COVID-19 age. An intelligent privacy protection with higher effect for the end users is an urgent problem in long distance education. In view of the risk of privacy disclosure of location, social network and trajectory of end users in the education system, this paper deletes the location information in the location set to protect the privacy of end user by providing the anonymous set to location. Firstly, this paper divides the privacy level of social networks by weighted sensitivity, and collects the anonymous set in social networks according to the level; Secondly, after the best anonymous set is generated by taking the data utility loss function as the standard, it was split to get an anonymous graph to hide the social network information; Finally, the trajectory anonymous set is constructed to hide the user trajectory with the l-difference privacy protection algorithm. Experiments show that the algorithm presented in this paper is superior to other algorithms no matter how many anonymous numbers there are, and the gap between relative anonymity levels is as large as 5.1 and 6.7. In addition, when the privacy protection intensity is 8, the trajectory loss rate presented in this paper tends to be stable, ranging from 0.005 to 0.007, all of which are less than 0.01. Meanwhile, its clustering effect is good. Therefore, the proportion of insecure anonymous sets in the algorithm in this paper is small, the trajectory privacy protection effect is good, and the location, social network and trajectory privacy of distance education end users are effectively protected.

Trajectory Privacy Protection Mechanism based on Salp-Like Swarm Algorithm

Location-based services have been widely used in daily life, providing diversified services for users. However, users may face the risk of trajectory privacy disclosure while enjoying the convenience of location-based services. Most of the existing trajectory protection schemes cannot match the road network and are vulnerable to attacks based on background information. In this paper, the concept of salp swarm algorithm is introduced to construct salp-like swarm algorithm, which can generate K−1 false trajectories that are highly similar to real trajectories. It is difficult for attackers to distinguish them. Besides, a road network matching model is designed in order to match the proposed trajectory privacy protection algorithm with the real road network environment, so that the effect of trajectory privacy protection is improved. Morever, a false location selection mechanism is proposed to find false location points, which not only considers the location and speed of users, but also ensures that the selection of false location points is more in line with the road network environment. The experimental results show that, under the condition of satisfying the same service quality, the trajectory privacy leakage probability of this scheme is reduced by 33% compared with the existing schemes, and it has better privacy protection effect.

Personalized trajectory privacy-preserving method based on sensitive attribute generalization and location perturbation

Trajectory data may include the user’s occupation, medical records, and other similar information. However, attackers can use specific background knowledge to analyze published trajectory data and access a user’s private information. Different users have different requirements regarding the anonymity of sensitive information. To satisfy personalized privacy protection requirements and minimize data loss, we propose a novel trajectory privacy preservation method based on sensitive attribute generalization and trajectory perturbation. The proposed method can prevent an attacker who has a large amount of background knowledge and has exchanged information with other attackers from stealing private user information. First, a trajectory dataset is clustered and frequent patterns are mined according to the clustering results. Thereafter, the sensitive attributes found within the frequent patterns are generalized according to the user requirements. Finally, the trajectory locations are perturbed to achieve trajectory privacy protection. The results of theoretical analyses and experimental evaluations demonstrate the effectiveness of the proposed method in preserving personalized privacy in published trajectory data.

An optimized differential privacy scheme with reinforcement learning in VANET

The protection of vehicle trajectory in Vehicular ad hoc network is facing many challenges. Among these challenges, one of the most critical issues is to keep the balance between geographical location protection and semantic location protection. Traditional trajectory protection schemes either only focus on geographical location protection or only semantic location protection. Moreover, when trajectory privacy protection is carried out, each location is often given the same protection. This may lead to sensitive locations under insufficient protection and unimportant locations under overprotection. In this paper, based on differential privacy, we propose an optimized privacy differential privacy scheme with reinforcement learning in vehicular ad hoc network. The proposed scheme can dynamically optimize the privacy budget allocation for each location on the vehicle trajectory to reach a better balance between geolocation obfuscation and semantic security. Experiments results demonstrate that the proposed scheme can reduce the risk of geographical and semantic location leakage, and therefore ensure the balance between the utility and privacy.

A Trajectory Privacy Protection Method Based on Random Sampling Differential Privacy

With the popularity of location-aware devices (e.g., smart phones), a large number of trajectory data were collected. The trajectory dataset can be used in many fields including traffic monitoring, market analysis, city management, etc. The collection and release of trajectory data will raise serious privacy concerns for users. If users’ privacy is not protected enough, they will refuse to share their trajectory data. In this paper, a new trajectory privacy protection method based on random sampling differential privacy (TPRSDP), which can provide more security protection, is proposed. Compared with other methods, it takes less time to run this method. Experiments are conducted on two real world datasets to validate the proposed scheme, and the results are compared with others in terms of running time and information loss. The performance of the scheme with different parameter values is verified. The setting of the new scheme parameters is discussed in detail, and some valuable suggestions are given.

Differential privacy trajectory data protection scheme based on R-tree

With the popularization of mobile devices with positioning functions, location-based service (LBS) plays a vital role in people's daily lives. The problem of privacy leakage becomes more and more critical. Although the application technology of LBS is developing rapidly, the corresponding privacy protection technology is growing slowly. At present, differential privacy technology has received attention from many researchers, but it is not easy to reasonably apply it to trajectory privacy protection. Most trajectory privacy protection models only focus on the spatial location of mobile users without considering the temporal characteristics of the trajectory, which destroys the spatial–temporal characteristics of the trajectory. Therefore, to beat this difficult problem, a differential privacy trajectory data protection scheme based on R-tree is suggested. Firstly, the trajectory similarity tree structure is proposed on the basis of R-tree index structure to realize the trajectory data's spatial storage and query processing. Secondly, the DPTS-tree (Differential Privacy Trajectory Similarity tree, DPTS-tree) is constructed with differential privacy technology, adding noise to the statistical values of mobile users in the nodes, which can greatly improve the ability to resist arbitrary background knowledge attacks and achieve the purpose of protecting data privacy. Then, to resist other information inference attacks in the trajectory data, when constructing the DPTS-tree, random noise is added to location data and other data in the trajectory. Finally, the algorithm is subjected to consistency constraints to address the problem that the added independent noise may cause data inconsistency. Experiments show that our algorithm can effectively protect sensitive and private information of users and ensure the usability of trajectory data.