An Efficient PIR Construction using Trusted Hardware

Office of Research,Singapore Management Universit

A new hardware-assisted PIR with O(n) shuffle cost

Ministry of Education, Singapore under its Academic Research Funding Tier

Shortest Path Computation with No Information Leakage

Shortest path computation is one of the most common queries in location-based services (LBSs). Although particularly useful, such queries raise serious privacy concerns. Exposing to a (potentially untrusted) LBS the client's position and her destination may reveal personal information, such as social habits, health condition, shopping preferences, lifestyle choices, etc. The only existing method for privacy-preserving shortest path computation follows the obfuscation paradigm; it prevents the LBS from inferring the source and destination of the query with a probability higher than a threshold. This implies, however, that the LBS still deduces some information (albeit not exact) about the client's location and her destination. In this paper we aim at strong privacy, where the adversary learns nothing about the shortest path query. We achieve this via established private information retrieval techniques, which we treat as black-box building blocks. Experiments on real, large-scale road networks assess the practicality of our schemes.Comment: VLDB201

Privacy-Preserving Shortest Path Computation

Navigation is one of the most popular cloud computing services. But in virtually all cloud-based navigation systems, the client must reveal her location and destination to the cloud service provider in order to learn the fastest route. In this work, we present a cryptographic protocol for navigation on city streets that provides privacy for both the client's location and the service provider's routing data. Our key ingredient is a novel method for compressing the next-hop routing matrices in networks such as city street maps. Applying our compression method to the map of Los Angeles, for example, we achieve over tenfold reduction in the representation size. In conjunction with other cryptographic techniques, this compressed representation results in an efficient protocol suitable for fully-private real-time navigation on city streets. We demonstrate the practicality of our protocol by benchmarking it on real street map data for major cities such as San Francisco and Washington, D.C.Comment: Extended version of NDSS 2016 pape

Shared and searchable encrypted data for untrusted servers

Current security mechanisms are not suitable for organisations that outsource their data management to untrusted servers. Encrypting and decrypting sensitive data at the client side is the normal approach in this situation but has high communication and computation overheads if only a subset of the data is required, for example, selecting records in a database table based on a keyword search. New cryptographic schemes have been proposed that support encrypted queries over encrypted data. But they all depend on a single set of secret keys, which implies single user access or sharing keys among multiple users, with key revocation requiring costly data re-encryption. In this paper, we propose an encryption scheme where each authorised user in the system has his own keys to encrypt and decrypt data. The scheme supports keyword search which enables the server to return only the encrypted data that satisfies an encrypted query without decrypting it. We provide a concrete construction of the scheme and give formal proofs of its security. We also report on the results of our implementation

Software-implemented attack tolerance for critical information retrieval

The fast-growing reliance of our daily life upon online information services often demands an appropriate level of privacy protection as well as highly available service provision. However, most existing solutions have attempted to address these problems separately. This thesis investigates and presents a solution that provides both privacy protection and fault tolerance for online information retrieval. A new approach to Attack-Tolerant Information Retrieval (ATIR) is developed based on an extension of existing theoretical results for Private Information Retrieval (PIR). ATIR uses replicated services to protect a user's privacy and to ensure service availability. In particular, ATIR can tolerate any collusion of up to t servers for privacy violation and up to ƒ faulty (either crashed or malicious) servers in a system with k replicated servers, provided that k ≥ t + ƒ + 1 where t ≥ 1 and ƒ ≤ t. In contrast to other related approaches, ATIR relies on neither enforced trust assumptions, such as the use of tanker-resistant hardware and trusted third parties, nor an increased number of replicated servers. While the best solution known so far requires k (≥ 3t + 1) replicated servers to cope with t malicious servers and any collusion of up to t servers with an O(n^*^) communication complexity, ATIR uses fewer servers with a much improved communication cost, O(n1/2)(where n is the size of a database managed by a server).The majority of current PIR research resides on a theoretical level. This thesis provides both theoretical schemes and their practical implementations with good performance results. In a LAN environment, it takes well under half a second to use an ATIR service for calculations over data sets with a size of up to 1MB. The performance of the ATIR systems remains at the same level even in the presence of server crashes and malicious attacks. Both analytical results and experimental evaluation show that ATIR offers an attractive and practical solution for ever-increasing online information applications