String Sanitization: A Combinatorial Approach

String data are often disseminated to support applications such as location-based service provision or DNA sequence analysis. This dissemination, however, may expose sensitive patterns that model confidential knowledge (e.g., trips to mental health clinics from a string representing a user’s loc

FOUGERE: User-Centric Location Privacy in Mobile Crowdsourcing Apps

International audienceMobile crowdsourcing is being increasingly used by industrial and research communities to build realistic datasets. By leveraging the capabilities of mobile devices, mobile crowdsourcing apps can be used to track participants' activity and to collect insightful reports from the environment (e.g., air quality, network quality). However, most of existing crowdsourced datasets systematically tag data samples with time and location stamps, which may inevitably lead to user privacy leaks by discarding sensitive information. This paper addresses this critical limitation of the state of the art by proposing a software library that improves user privacy without compromising the overall quality of the crowdsourced datasets. We propose a decentralized approach, named Fougere, to convey data samples from user devices to third-party servers. By introducing an a priori data anonymization process, we show that Fougere defeats state-of-the-art location-based privacy attacks with little impact on the quality of crowd-sourced datasets

Hiding sensitive knowledge without side effects

Sensitive knowledge hiding in large transactional databases is one of the major goals of privacy preserving data mining. However, it is only recently that researchers were able to identify exact solutions for the hiding of knowledge, depicted in the form of sensitive frequent itemsets and their related association rules. Exact solutions allow for the hiding of vulnerable knowledge without any critical compromises, such as the hiding of nonsensitive patterns or the accidental uncovering of infrequent itemsets, amongst the frequent ones, in the sanitized outcome. In this paper, we highlight the process of border revision, which plays a significant role towards the identification of exact hiding solutions, and we provide efficient algorithms for the computation of the revised borders. Furthermore, we review two algorithms that identify exact hiding solutions, and we extend the functionality of one of them to effectively identify exact solutions for a wider range of problems (than its original counterpart). Following that, we introduce a novel framework for decomposition and parallel solving of hiding problems, which are handled by each of these approaches. This framework improves to a substantial degree the size of the problems that both algorithms can handle and significantly decreases their runtime. Through experimentation, we demonstrate the effectiveness of these approaches toward providing high quality knowledge hiding solutions

Subframe Temporal Alignment of Non-Stationary Cameras

This paper studies the problem of estimating the sub-frame temporal off-set between unsychronized, non-stationary cameras. Based on motion trajec-tory correspondences, the estimation is done in two steps. First, we propose an algorithm to robustly estimate the frame accurate offset by analyzing the trajectories and matching their characteristic time patterns. Using this result, we then show how the estimation of the fundamental matrix between two cameras can be reformulated to yield the sub-frame accurate offset from nine correspondences. We verify the robustness and performance of our approach on synthetic data as well as on real video sequences.

String sanitization: a combinatorial approach

String data are often disseminated to support applications such as location-based service provision or DNA sequence analysis. This dissemination, however, may expose sensitive patterns that model confidential knowledge (e.g., trips to mental health clinics from a string representing a user’s location history). In this paper, we consider the problem of sanitizing a string by concealing the occurrences of sensitive patterns, while maintaining data utility. First, we propose a time-optimal algorithm, TFS-ALGO, to construct

Towards String Sanitization

Part 3: MHDWInternational audienceAn increasing number of applications, in domains ranging from bio-medicine to business and to pervasive computing, feature data represented as a long sequence of symbols (string). Sharing these data, however, may lead to the disclosure of sensitive patterns which are represented as substrings and model confidential information. Such patterns may model, for example, confidential medical knowledge, business secrets, or signatures of activity patterns that may risk the privacy of smart-phone users. In this paper, we study the novel problem of concealing a given set of sensitive patterns from a string. Our approach is based on injecting a minimal level of uncertainty to the string, by replacing selected symbols in the string with a symbol “$$*$$∗” that is interpreted as any symbol from the set of possible symbols that may appear in the string. To realize our approach, we propose an algorithm that efficiently detects occurrences of the sensitive patterns in the string and then sanitizes these sensitive patterns. We also present a preliminary set of experiments to demonstrate the effectiveness and efficiency of our algorithm