Electronic health records (EHRs), digitization of patients' health record, offer many advantages over traditional ways of keeping patients' records, such as easing data management and facilitating ...quick access and real-time treatment. EHRs are a rich source of information for research (e.g. in data analytics), but there is a risk that the published data (or its leakage) can compromise patient privacy. The k-anonymity model is a widely used privacy model to study privacy breaches, but this model only studies privacy against identity disclosure. Other extensions to mitigate existing limitations in k-anonymity model include p-sensitive k-anonymity model, p+-sensitive k-anonymity model, and (p, α)-sensitive k-anonymity model. In this paper, we point out that these existing models are inadequate in preserving the privacy of end users. Specifically, we identify situations where p+-sensitive k-anonymity model is unable to preserve the privacy of individuals when an adversary can identify similarities among the categories of sensitive values. We term such attack as Categorical Similarity Attack (CSA). Thus, we propose a balanced p+-sensitive k-anonymity model, as an extension of the p+-sensitive k-anonymity model. We then formally analyze the proposed model using High-Level Petri Nets (HLPN) and verify its properties using SMT-lib and Z3 solver. We then evaluate the utility of release data using standard metrics and show that our model outperforms its counterparts in terms of privacy vs. utility tradeoff.
With the increasing popularity of location-based services (LBSs), there is a corresponding increase in the potential for location privacy leakage. Existing solutions generally introduce a ...fully-trusted third party between the users and the location service provider (LSP). However, such an approach offers limited privacy guarantees and incurs high communication overhead. Specifically, once a fully-trusted third party is compromised, user information would likely be exposed. In this paper, we propose a solution designed to enhance location privacy in LBSs. Our scheme is based on the uniform grid, and adopts both order-preserving symmetric encryption (OPSE) andk-anonymity technique. Thus, the anonymizer knows nothing about a user’s real location, and it can only implement simple matching and comparison operations. In our approach, we also employ an entity (hereafter referred to as the converter) to transform the user-defined grid structure into the uniform grid structure. This combined with the caching mechanism, allow us to avoid repeated queries from different users on the same query spatial region and consequently, reduce the overhead of the LBS server. The analysis and simulation results demonstrate that our proposal can effectively preserve a user’s location privacy, with reduced overheads at the anonymizer and the LBS server.
•We present a novel UGC scheme to enhance location privacy in LBSs.•We utilize thek-anonymity principle to improve the user’s location privacy.•We design the matching and comparison mechanism based on coordinates and identifiers.•We employ the uniform grid structure and caching to improve users’ privacy.
In crowdsourcing systems, requesters publish tasks, and interested workers provide answers to get rewards. Worker anonymity motivates participation since it protects their privacy. Anonymity with ...unlinkability is an enhanced version of anonymity because it makes it impossible to "link" workers across the tasks they participate in. Another core feature of crowdsourcing systems is worker quality which expresses a worker's trustworthiness and quantifies their historical performance. In this work, we present AVeCQ, the first crowdsourcing system that reconciles these properties, achieving enhanced anonymity and verifiable worker quality updates. AVeCQ relies on a suite of cryptographic tools, such as zero-knowledge proofs, to (i) guarantee workers' privacy, (ii) prove the correctness of worker quality scores and task answers, and (iii) commensurate payments. AVeCQ is developed modularly, where requesters and workers communicate over a platform that supports pseudonymity, information logging, and payments. To compare AVeCQ with the state-ofthe-art, we prototype it over Ethereum. AVeCQ outperforms the state-of-the-art in three popular crowdsourcing tasks (image annotation, average review, and Gallup polls). E.g., for an Average Review task with 5 choices and 128 workers AVeCQ is 40% faster (including computing and verifying necessary proofs, and blockchain transaction processing overheads) with the task's requester consuming 87% fewer gas.
For anonymous communication networks (ACNs), Das et al. recently confirmed a long-suspected trilemma result that ACNs cannot achieve strong anonymity, low latency overhead and low bandwidth overhead ...at the same time. Our paper emanates from the careful observation that their analysis does not include a relevant class of ACNs with what we call
where users proactively work together towards improving their anonymity. We show that such protocols can achieve better anonymity than predicted by the above trilemma result. As the main contribution, we present a stronger impossibility result that includes all ACNs we are aware of. Along with our formal analysis, we provide intuitive interpretations and lessons learned. Finally, we demonstrate qualitatively stricter requirements for the Anytrust assumption (all but one protocol party is compromised) prevalent across ACNs.
Permissionless blockchain, as a kind of distributed ledger, has gained considerable attention because of its openness, transparency, decentralization, and immutability. Currently, permissionless ...blockchain has shown a good application prospect in many fields, from the initial cryptocurrency to the Internet of Things (IoT) and Vehicular Ad-Hoc Networking (VANET), which is considered as the beginning of rewriting our digital infrastructure. However, blockchain confronts some privacy risks that hinder its practical applications. Though numerous surveys reviewed the privacy preservation in blockchain, they failed to reveal the latest advances, nor have they been able to conduct a unified standard comprehensive classification of the privacy protection of permissionless blockchain. Therefore, in this paper, we analyze the specific characteristics of permissionless blockchain, summarize the potential privacy threats, and investigate the unique privacy requirements of blockchain. Existing privacy preservation technologies are carefully surveyed and evaluated based on our proposed evaluation criteria. We finally figure out open research issues as well as future research directions from the perspective of privacy issues.
Internet of Things (IoT) is playing an important role after its showing up, it covers from traditional equipment to general household objects such as WSNs and RFID. With the great potential of IoT, ...there come all kinds of challenges. This paper focuses on the security problems among all other challenges. As IoT is built on the basis of the Internet, security problems of the Internet will also show up in IoT. Moreover, as IoT contains three layers: perception layer, transportation layer and application layer, this paper will analyze the security problems of each layer separately and try to find new problems and solutions. This paper also analyzes the cross-layer heterogeneous integration issues and security issues in detail and discusses the security issues of IoT as a whole and tries to find solutions to them. In the end, this paper compares security issues between IoT and traditional network, and discusses opening security issues of IoT.
•Analyzes the cross-layer heterogeneous integration issues and security issues in detail.•Discusses the security issues of IoT as a whole and discuss the solution.•Compares the security issues between IoT and traditional network, and discusses opening security issues of IoT.
Tor Dingledine et al. 2004 is the most widely used anonymity network today, serving millions of users on a daily basis using a growing number of volunteer-run routers. Since its deployment in 2003, ...there have been more than three dozen proposals that aim to improve its performance, security, and unobservability. Given the significance of this research area, our goal is to provide the reader with the state of current research directions and challenges in anonymous communication systems, focusing on the Tor network. We shed light on the design weaknesses and challenges facing the network and point out unresolved issues.
While enjoying the convenience brought by Location Based Service (LBS), the location privacy of vehicles in VANET may be disclosed. Distributed k-anonymity, as one of the most popular privacy ...protection methods, fails to take the trustworthiness of participants into account, resulting in malicious tracing of vehicles, which further leads to the sensitive information leakage, and even the safety threat of personal property. To address this issue, we propose a blockchain enabled trust-based location privacy protection scheme in VANET. Specifically, by analyzing the different requirements of the request vehicle and the cooperative vehicle during the process of constructing the anonymous cloaking region, as well as combining the characteristics of these two roles, we devise the trust management method based on Dirichlet distribution, such that both the requester and the cooperator will only cooperate with the vehicles they trust. Moreover, by employing blockchain, we also proposed the data structure to record the trustworthiness of vehicles on publicly available blocks timely, so that any vehicle can access the historical trust information of counterparties whenever necessary. Finally, the construction process of anonymous cloaking region is presented. Security analysis and extensive experiments indicate that the proposal is resilient to various trust model attacks, it can effectively detect the malicious vehicles, and preserve the location privacy of vehicles in the anonymous cloaking region construction, while the required time delay is limited.
Massive volumes of data are being generated at every moment through various sources in the cyber-physical world. While storing as well as facilitating these data for business or individual ...requirements, data disclosure, sensitive data leakage, and privacy breaches are important concerns to both service providers and service consumers. Many privacy-preserving data publishing models came into existence to protect data security and privacy from disclosure. Background knowledge has been an important data source to the adversary and has become a potential threat to many privacy-preserving data publishing models. Background knowledge allows the adversary to reveal sensitive information of an individual from the published data. In this paper, we formalize background knowledge by defining different knowledge sets. We present a privacy model against the given background knowledge. We analyze the conventional privacy-preserving data publishing models such as k-anonymity, l-diversity, and t-closeness against the background knowledge attacks and show that all these privacy models fail to preserve privacy against the comprehensive background knowledge adversarial model, which we formalized in this work. Comprehensive background knowledge attacks in privacy-preserving data publishing models are practical in many real-world applications, and we believe that the privacy model presented in this work advances the research findings in the area.
Why do people use anonymity-granting technologies when surfing the Internet? Anecdotal evidence suggests that people often resort to using online anonymity services, like the Tor network, because ...they are concerned about the possibility of their government infringing their civil and political rights, especially in highly repressive regimes. This claim has yet to be subject to rigorous cross-national, over time testing. In this article, econometric analysis of newly compiled data on Tor network usage from 2011 to 2013 shows that the relationship between political repression and the use of the Tor network is U-shaped. Political repression drives usage of Tor the most in both highly repressive and highly liberal contexts. The shape of this relationship plausibly emerges as a function of people’s opportunity to use Tor and their need to use anonymity-granting technologies to express their basic political rights in highly repressive regimes.
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