Usually, a proof of a theorem contains more knowledge than the mere fact that the theorem is true. For instance, to prove that a graph is Hamiltonian it suffices to exhibit a Hamiltonian tour in it; however, this seems to contain more knowledge than the single bit Hamiltonian/non-Hamiltonian.In this paper a computational complexity theory of the “knowledge” contained in a proof is developed. Zero-knowledge proofs are defined as those proofs that convey no additional knowledge other than the correctness of the proposition in question. Examples of zero-knowledge proof systems are given for the languages of quadratic residuosity and 'quadratic nonresiduosity. These are the first examples of zero-knowledge proofs for languages not known to be efficiently recognizable.

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The knowledge complexity of interactive proof-systems

We describe a novel approach for two-party private set intersection (PSI) with semi-honest security. Compared to existing PSI protocols, ours has a more favorable balance between communication and computation. Specifically, our protocol has the lowest monetary cost of any known PSI protocol, when run over the Internet using cloud-based computing services (taking into account current rates for CPU + data). On slow networks (e.g., 10 Mbps) our protocol is actually the fastest.

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SpOT-Light: Lightweight Private Set Intersection from Sparse OT Extension.

Anonymization is a practical solution for preserving user’s privacy in data publishing. Data owners such as hospitals, banks, social network (SN) service providers, and insurance companies anonymize their user’s data before publishing it to protect the privacy of users whereas anonymous data remains useful for legitimate information consumers. Many anonymization models, algorithms, frameworks, and prototypes have been proposed/developed for privacy preserving data publishing (PPDP). These models/algorithms anonymize users’ data which is mainly in the form of tables or graphs depending upon the data owners. It is of paramount importance to provide good perspectives of the whole information privacy area involving both tabular and SN data, and recent anonymization researches. In this paper, we presents a comprehensive survey about SN (i.e., graphs) and relational (i.e., tabular) data anonymization techniques used in the PPDP. We systematically categorize the existing anonymization techniques into relational and structural anonymization, and present an up to date thorough review on existing anonymization techniques and metrics used for their evaluation. Our aim is to provide deeper insights about the PPDP problem involving both graphs and tabular data, possible attacks that can be launched on the sanitized published data, different actors involved in the anonymization scenario, and major differences in amount of private information contained in graphs and relational data, respectively. We present various representative anonymization methods that have been proposed to solve privacy problems in application-specific scenarios of the SNs. Furthermore, we highlight the user’s re-identification methods used by malevolent adversaries to re-identify people uniquely from the privacy preserved published data. Additionally, we discuss the challenges of anonymizing both graphs and tabular data, and elaborate promising research directions. To the best of our knowledge, this is the first work to systematically cover recent PPDP techniques involving both SN and relational data, and it provides a solid foundation for future studies in the PPDP field.

Anonymization Techniques for Privacy Preserving Data Publishing: A Comprehensive Survey

Vehicular ad hoc networks (VANETs) have stimulated interests in both academic and industry settings. Once deployed, they would bring a new driving experience to drivers. However, in an open-access environment, privacy is one of the greatest challenges, as drivers want to keep their personal information protected. Therefore, many authentication protocols have been proposed as solutions to the privacy issue. In most of the existing protocols, to prevent the revoked entity from generating a valid authentication information, the verifiers must frequently download the revocation list from one or more remote authorities to keep the list up-to-date, which greatly increases the workload of the remote authority. In this paper, to cope with such challenging concerns, based on the idea of group signatures, we propose a novel authentication protocol scheme by using the complete sub-tree method to achieve membership revocation, which ensures forward security. In our scheme, the verifiers can verify the authentication information by getting the latest epoch $t$ without having to obtain the latest revocation list. In the aspect of security, the proposed protocol is featured with forward security, CCA2-anonymity, unforgeability, non-frameability, and traceability. In addition, our scheme adopts a decentralized group model, so that the whole domain of VANETs is divided into sub-regions and any vehicle has to update its non-revoked token periodically from the regional group manager who manages the region where the vehicle stays.

An Efficient and Secure Anonymous Authentication Scheme for VANETs Based on the Framework of Group Signatures

Attribute-based encryption (ABE) is suitable for mobile cloud storage to protect data confidentiality and realize fine-grained data access control. It is essential for ABE schemes to achieve attribute revocation as users’ attributes may be changed frequently. Keyword search over encrypted data also needs to be solved in the mobile cloud storage. In addition, computational efficiency is a consideration for the resource-constrained mobile device. Focusing on the above-mentioned problems, an efficiently revocable and searchable ABE (RSABE) scheme for the mobile cloud storage is proposed. In our scheme, the function of attribute revocation is efficiently achieved by delegating the update of secret key and ciphertext to the powerful cloud server. Keyword search is also supported, in which data owners and users can generate the keywords index and search trapdoor, respectively, without relying on always online trusted authority. Furthermore, an outsourced decryption technology is used to reduce the computational load of decryption on user side. Our RSABE scheme is proven to be semantically secure against selective ciphertext policy and chosen plaintext attack, and to be secure against chosen keyword attack in the random oracle model. Finally, performance evaluation demonstrates that our scheme is highly efficient.

Efficiently Revocable and Searchable Attribute-Based Encryption Scheme for Mobile Cloud Storage

Conjunctive searchable encryption is an efficient way to perform multi-keyword search over encrypted data in cloud storage. However, most existing methods do not take into account the integrity verification of the search result. Moreover, existing integrity verification methods can only verify the integrity of single-keyword search results, which cannot meet the requirements of conjunctive search. To address this problem, we proposed a conjunctive keyword searchable encryption scheme with an authentication mechanism that can efficiently verify the integrity of search results. The proposed scheme is based on the dynamic searchable symmetric encryption and adopts the Merkle tree and bilinear map accumulator to prove the correctness of set operations. It supports conjunctive keyword as input for conjunctive search and gives the server the ability to prove the integrity of the search result to the user. Formal proofs and extensive experiments show that the proposed scheme is efficient, unforgeable and adaptive secure against chosen-keyword attacks.

Integrity-verifiable conjunctive keyword searchable encryption in cloud storage

Electronic cash is an electronic form of currency, which allows the cash transactions over communication networks under privacy protections. However, it still has some aspects that have not been well studied. Known constructions suffer from at least one of the following limitations: 1 relying on a random oracle, 2 not supporting multiple bank setting and users dynamically joining or 3 prohibitively expensive. In this paper, we propose a new electronic cash system that avoids all these limitations. In other words, our system is anonymous against chosen-ciphertext attack CCA in the standard model, and supports multiple banks enrolling and users dynamically joining, which is achieved by the utilization of non-interactive zero-knowledge proof and dynamic group signature. Finally, in the standard model, a formal security proof is given to claim that our system has CCA anonymity, unforgeability, traceability and no double-spending. Compared with the existing systems, ours has advantages of both the efficiency and security.

The electronic cash system based on non-interactive zero-knowledge proofs

A wide range of applications can benefit from storing and managing data as graph structures, and graph theory algorithms can be used to solve various computing problems. In this paper, we propose a secure two-party private graph intersection protocol against semi-honest servers. The protocol allows a server and a client, each holding a private graph, to jointly compute the intersection of their graphs. The protocol utilizes homomorphic encryptions and a private set intersection sub-protocol to prevent information leakage during the process. At the end of the protocol, the server learns the graph intersection, and the client learns the vertex intersection.

Private Graph Intersection Protocol

Searchable symmetric encryption is an efficient way to perform keyword search over encrypted data in cloud storage. However, most existing methods do not take into account the integrity verification of the search result. Moreover, existing methods can only verify the integrity of single-keyword search results, which cannot meet the requirements of multi-keyword conjunctive search. To address this problem, we proposed a multi-keyword searchable encryption scheme with an authentication mechanism that can efficiently verify the integrity of search results. The proposed scheme is based on the searchable symmetric encryption and adopts the bilinear map accumulator to prove the correctness of set operations. It supports multiple keywords as input for conjunctive search and gives the server the ability to prove the integrity of the search result to the user. Formal proofs show that the proposed scheme is unforgeable and adaptive secure against chosen-keyword attacks. To the best of our knowledge, this is the first work that can authenticate the multi-keyword search result over encrypted data.

Integrity Preserving Multi-keyword Searchable Encryption for Cloud Computing

Graph data structure has been widely used across many application areas, such as web data, social network, and cheminformatics. The main benefit of storing data as graphs is there exists a rich set...

Yuxi Li

Papers

Integrity-verifiable conjunctive keyword searchable encryption in cloud storage

The electronic cash system based on non-interactive zero-knowledge proofs

Private Graph Intersection Protocol

Integrity Preserving Multi-keyword Searchable Encryption for Cloud Computing

Privacy-Preserving Subgraph Matching Protocol for Two Parties