Short Group Signature without Random Oracles

We construct a short group signature which is proven secure without random oracles. By making certain reasonable assumptions and applying the technique of non-interactive proof system, we prove that our scheme is full anonymity and full traceability. Compared with other related works, such as BW06, BW07, ours is more practical due to the short size of both public key and group signature

Distributed Multi-authority Attribute-based Encryption Scheme for Friend Discovery in Mobile Social Networks

AbstractIn recent years, the rapid expansion of the capability of portable devices, cloud servers and cellular network technologies is the wind beneath the wing of mobile social networks. Compared to traditional web-based online social networks, the mobile social networks can assist users to easily discover and make new social interaction with others. A challenging task is to protect the privacy of the users’ profiles and communications. Existing works are mainly based on traditional cryptographic methods, such as homomorphic and group signatures, which are very computationally costly. In this paper, we propose a novel distributed multi-authority attribute-based encryption scheme to efficiently achieve privacy-preserving without additional special signatures. In addition, the proposed scheme can achieve fine-grained and flexible access control. Detailed analysis demonstrates the effectiveness and practicability of our scheme

Group signature revocable anonymity scheme for network monitoring

Subscriber’s Privacy is in a constant conflict with security and accountability providing controls employed for network monitoring activities of service providers and enterprises. This paper presents the results of the author’s research in the field of distributed network security monitoring architectures and the proposal of such a system that incorporates cryptographic protocols and a group signature scheme to deliver privacy protecting, network surveillance system architecture that provides subscriber’s accountability and controlled, revocable anonymity

Privacy-preserving security solution for cloud services

AbstractWe propose a novel privacy-preserving security solution for cloud services. Our solution is based on an efficient non-bilinear group signature scheme providing the anonymous access to cloud services and shared storage servers. The novel solution offers anonymous authenticationfor registered users. Thus, users' personal attributes (age, valid registration, successful payment) can be proven without revealing users' identity, and users can use cloud services without any threat of profiling their behavior. However, if a user breaks provider's rules, his access right is revoked. Our solution provides anonymous access, unlinkability and the confidentiality of transmitted data. We implement our solution as a proof of concept applicationand present the experimental results. Further, we analyzecurrent privacy preserving solutions for cloud services and group signature schemes as basic parts of privacy enhancing solutions in cloud services. We compare the performance of our solution with the related solutionsand schemes

Privacy-Preserving Ride Sharing Scheme for Autonomous Vehicles

The transport sector is set to undergo an overall change with the advent of autonomous vehicles embedded with artificial intelligence and machine learning. Autonomous vehicles will not only make the road safer but also will improve the efficiency of the modern transport system. Ride sharing is a major gamechanger in the transport industry. Autonomous Vehiclescan make ride sharingpopular, convenientand necessary because it eliminates the need of a driver and will help in recuperating the initial cost of the vehicle. In current scenario, the organization of ride sharing requires the users to disclose sensitive private information not only about the pick-up and drop-off locations but also other details such as name and contact details. In this paper, we propose a scheme to facilitate ride sharing and address the privacy issues that plague down the current industry. The scheme encrypts data using similarity measurement technique to preserve the privacy of the user. The ride sharing route is divided into cells, which is further represented by one bit in a binary vector. Binary vectors are used to represent the trip data of each user.The encryption of the vector data is submitted to a server. The server can measure the similarity of the users’ trip data and find other users who can share rides along the same route without knowing the data. The proposed scheme can facilitate ride sharing without disclosing private information. The scheme is implemented using Visual C on a real map. The measurements from the results have confirmed that the scheme is effective when ride sharing becomes popular and the server needs to organize a large number of rides in short time

Privacy Preserving Cryptographic Protocols for Secure Heterogeneous Networks

Disertační práce se zabývá kryptografickými protokoly poskytující ochranu soukromí, které jsou určeny pro zabezpečení komunikačních a informačních systémů tvořících heterogenní sítě. Práce se zaměřuje především na možnosti využití nekonvenčních kryptografických prostředků, které poskytují rozšířené bezpečnostní požadavky, jako je například ochrana soukromí uživatelů komunikačního systému. V práci je stanovena výpočetní náročnost kryptografických a matematických primitiv na různých zařízeních, které se podílí na zabezpečení heterogenní sítě. Hlavní cíle práce se zaměřují na návrh pokročilých kryptografických protokolů poskytujících ochranu soukromí. V práci jsou navrženy celkově tři protokoly, které využívají skupinových podpisů založených na bilineárním párování pro zajištění ochrany soukromí uživatelů. Tyto navržené protokoly zajišťují ochranu soukromí a nepopiratelnost po celou dobu datové komunikace spolu s autentizací a integritou přenášených zpráv. Pro navýšení výkonnosti navržených protokolů je využito optimalizačních technik, např. dávkového ověřování, tak aby protokoly byly praktické i pro heterogenní sítě.The dissertation thesis deals with privacy-preserving cryptographic protocols for secure communication and information systems forming heterogeneous networks. The thesis focuses on the possibilities of using non-conventional cryptographic primitives that provide enhanced security features, such as the protection of user privacy in communication systems. In the dissertation, the performance of cryptographic and mathematic primitives on various devices that participate in the security of heterogeneous networks is evaluated. The main objectives of the thesis focus on the design of advanced privacy-preserving cryptographic protocols. There are three designed protocols which use pairing-based group signatures to ensure user privacy. These proposals ensure the protection of user privacy together with the authentication, integrity and non-repudiation of transmitted messages during communication. The protocols employ the optimization techniques such as batch verification to increase their performance and become more practical in heterogeneous networks.

Security and Privacy Preservation in Vehicular Social Networks

Improving road safety and traffic efficiency has been a long-term endeavor for the government, automobile industry and academia. Recently, the U.S. Federal Communication Commission (FCC) has allocated a 75 MHz spectrum at 5.9 GHz for vehicular communications, opening a new door to combat the road fatalities by letting vehicles communicate to each other on the roads. Those communicating vehicles form a huge Ad Hoc Network, namely Vehicular Ad Hoc Network (VANET). In VANETs, a variety of applications ranging from the safety related (e.g. emergence report, collision warning) to the non-safety related (e.g., delay tolerant network, infortainment sharing) are enabled by vehicle-to-vehicle (V-2-V) and vehicle-to-roadside (V-2-I) communications. However, the flourish of VANETs still hinges on fully understanding and managing the challenging issues over which the public show concern, particularly, security and privacy preservation issues. If the traffic related messages are not authenticated and integrity-protected in VANETs, a single bogus and/or malicious message can potentially incur a terrible traffic accident. In addition, considering VANET is usually implemented in civilian scenarios where locations of vehicles are closely related to drivers, VANET cannot be widely accepted by the public if VANET discloses the privacy information of the drivers, i.e., identity privacy and location privacy. Therefore, security and privacy preservation must be well addressed prior to its wide acceptance. Over the past years, much research has been done on considering VANET's unique characteristics and addressed some security and privacy issues in VANETs; however, little of it has taken the social characteristics of VANET into consideration. In VANETs, vehicles are usually driven in a city environment, and thus we can envision that the mobility of vehicles directly reflects drivers' social preferences and daily tasks, for example, the places where they usually go for shopping or work. Due to these human factors in VANETs, not only the safety related applications but also the non-safety related applications will have some social characteristics. In this thesis, we emphasize VANET's social characteristics and introduce the concept of vehicular social network (VSN), where both the safety and non-safety related applications in VANETs are influenced by human factors including human mobility, human self-interest status, and human preferences. In particular, we carry on research on vehicular delay tolerant networks and infotainment sharing --- two important non-safety related applications of VSN, and address the challenging security and privacy issues related to them. The main contributions are, i) taking the human mobility into consideration, we first propose a novel social based privacy-preserving packet forwarding protocol, called SPRING, for vehicular delay tolerant network, which is characterized by deploying roadside units (RSUs) at high social intersections to assist in packet forwarding. With the help of high-social RSUs, the probability of packet drop is dramatically reduced and as a result high reliability of packet forwarding in vehicular delay tolerant network can be achieved. In addition, the SPRING protocol also achieves conditional privacy preservation and resist most attacks facing vehicular delay tolerant network, such as packet analysis attack, packet tracing attack, and black (grey) hole attacks. Furthermore, based on the ``Sacrificing the Plum Tree for the Peach Tree" --- one of the Thirty-Six Strategies of Ancient China, we also propose a socialspot-based packet forwarding (SPF) protocol for protecting receiver-location privacy, and present an effective pseudonyms changing at social spots strategy, called PCS, to facilitate vehicles to achieve high-level location privacy in vehicular social network; ii) to protect the human factor --- interest preference privacy in vehicular social networks, we propose an efficient privacy-preserving protocol, called FLIP, for vehicles to find like-mined ones on the road, which allows two vehicles sharing the common interest to identify each other and establish a shared session key, and at the same time, protects their interest privacy (IP) from other vehicles who do not share the same interest on the road. To generalize the FLIP protocol, we also propose a lightweight privacy-preserving scalar product computation (PPSPC) protocol, which, compared with the previously reported PPSPC protocols, is more efficient in terms of computation and communication overheads; and iii) to deal with the human factor -- self-interest issue in vehicular delay tolerant network, we propose a practical incentive protocol, called Pi, to stimulate self-interest vehicles to cooperate in forwarding bundle packets. Through the adoption of the proper incentive policies, the proposed Pi protocol can not only improve the whole vehicle delay tolerant network's performance in terms of high delivery ratio and low average delay, but also achieve the fairness among vehicles. The research results of the thesis should be useful to the implementation of secure and privacy-preserving vehicular social networks

Security and Privacy Preservation in Mobile Social Networks

Social networking extending the social circle of people has already become an important integral part of our daily lives. As reported by ComScore, social networking sites such as Facebook and Twitter have reached 82 percent of the world's online population, representing 1.2 billion users around the world. In the meantime, fueled by the dramatic advancements of smartphones and the ubiquitous connections of Bluetooth/WiFi/3G/LTE networks, social networking further becomes available for mobile users and keeps them posted on the up-to-date worldwide news and messages from their friends and families anytime anywhere. The convergence of social networking, advanced smartphones, and stable network infrastructures brings us a pervasive and omnipotent communication platform, named mobile social network (MSN), helping us stay connected better than ever. In the MSN, multiple communication techniques help users to launch a variety of applications in multiple communication domains including single-user domain, two-user domain, user-chain domain, and user-star domain. Within different communication domains, promising mobile applications are fostered. For example, nearby friend search application can be launched in the two-user or user-chain domains to help a user find other physically-close peers who have similar interests and preferences; local service providers disseminate advertising information to nearby users in the user-star domain; and health monitoring enables users to check the physiological signals in the single-user domain. Despite the tremendous benefits brought by the MSN, it still faces many technique challenges among of which security and privacy protections are the most important ones as smartphones are vulnerable to security attacks, users easily neglect their privacy preservation, and mutual trust relationships are difficult to be established in the MSN. In this thesis, we explore the unique characteristics and study typical research issues of the MSN. We conduct our research with a focus on security and privacy preservation while considering human factors. Specifically, we consider the profile matching application in the two-user domain, the cooperative data forwarding in the user-chain domain, the trustworthy service evaluation application in the user-star domain, and the healthcare monitoring application in the single-user domain. The main contributions are, i) considering the human comparison behavior and privacy requirements, we first propose a novel family of comparison-based privacy-preserving profile matching (PPM) protocols. The proposed protocols enable two users to obtain comparison results of attribute values in their profiles, while the attribute values are not disclosed. Taking user anonymity requirement as an evaluation metric, we analyze the anonymity protection of the proposed protocols. From the analysis, we found that the more comparison results are disclosed, the less anonymity protection is achieved by the protocol. Further, we explore the pseudonym strategy and an anonymity enhancing technique where users could be self-aware of the anonymity risk level and take appropriate actions when needed; ii) considering the inherent MSN nature --- opportunistic networking, we propose a cooperative privacy-preserving data forwarding (PDF) protocol to help users forward data to other users. We indicate that privacy and effective data forwarding are two conflicting goals: the cooperative data forwarding could be severely interrupted or even disabled when the privacy preservation of users is applied, because without sharing personal information users become unrecognizable to each other and the social interactions are no longer traceable. We explore the morality model of users from classic social theory, and use game-theoretic approach to obtain the optimal data forwarding strategy. Through simulation results, we show that the proposed cooperative data strategy can achieve both the privacy preservation and the forwarding efficiency; iii) to establish the trust relationship in a distributed MSN is a challenging task. We propose a trustworthy service evaluation (TSE) system, to help users exchange their service reviews toward local vendors. However, vendors and users could be the potential attackers aiming to disrupt the TSE system. We then consider the review attacks, i.e., vendors rejecting and modifying the authentic reviews of users, and the Sybil attacks, i.e., users abusing their pseudonyms to generate fake reviews. To prevent these attacks, we explore the token technique, the aggregate signature, and the secret sharing techniques. Simulation results show the security and the effectiveness of the TSE system can be guaranteed; iv) to improve the efficiency and reliability of communications in the single-user domain, we propose a prediction-based secure and reliable routing framework (PSR). It can be integrated with any specific routing protocol to improve the latter's reliability and prevent data injection attacks during data communication. We show that the regularity of body gesture can be learned and applied by body sensors such that the route with the highest predicted link quality can always be chose for data forwarding. The security analysis and simulation results show that the PSR significantly increases routing efficiency and reliability with or without the data injection attacks