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 Issues in Wireless Mesh Networks: A Survey

This book chapter identifies various security threats in wireless mesh network (WMN). Keeping in mind the critical requirement of security and user privacy in WMNs, this chapter provides a comprehensive overview of various possible attacks on different layers of the communication protocol stack for WMNs and their corresponding defense mechanisms. First, it identifies the security vulnerabilities in the physical, link, network, transport, application layers. Furthermore, various possible attacks on the key management protocols, user authentication and access control protocols, and user privacy preservation protocols are presented. After enumerating various possible attacks, the chapter provides a detailed discussion on various existing security mechanisms and protocols to defend against and wherever possible prevent the possible attacks. Comparative analyses are also presented on the security schemes with regards to the cryptographic schemes used, key management strategies deployed, use of any trusted third party, computation and communication overhead involved etc. The chapter then presents a brief discussion on various trust management approaches for WMNs since trust and reputation-based schemes are increasingly becoming popular for enforcing security in wireless networks. A number of open problems in security and privacy issues for WMNs are subsequently discussed before the chapter is finally concluded.Comment: 62 pages, 12 figures, 6 tables. This chapter is an extension of the author's previous submission in arXiv submission: arXiv:1102.1226. There are some text overlaps with the previous submissio

Secure and Privacy-Preserving Authentication Protocols for Wireless Mesh Networks

Wireless mesh networks (WMNs) have emerged as a promising concept to meet the challenges in next-generation wireless networks such as providing flexible, adaptive, and reconfigurable architecture while offering cost-effective solutions to service providers. As WMNs become an increasingly popular replacement technology for last-mile connectivity to the home networking, community and neighborhood networking, it is imperative to design efficient and secure communication protocols for these networks. However, several vulnerabilities exist in currently existing protocols for WMNs. These security loopholes can be exploited by potential attackers to launch attack on WMNs. The absence of a central point of administration makes securing WMNs even more challenging. The broadcast nature of transmission and the dependency on the intermediate nodes for multi-hop communications lead to several security vulnerabilities in WMNs. The attacks can be external as well as internal in nature. External attacks are launched by intruders who are not authorized users of the network. For example, an intruding node may eavesdrop on the packets and replay those packets at a later point of time to gain access to the network resources. On the other hand, the internal attacks are launched by the nodes that are part of the WMN. On example of such attack is an intermediate node dropping packets which it was supposed to forward. This chapter presents a comprehensive discussion on the current authentication and privacy protection schemes for WMN. In addition, it proposes a novel security protocol for node authentication and message confidentiality and an anonymization scheme for privacy protection of users in WMNs.Comment: 32 pages, 10 figures. The work is an extended version of the author's previous works submitted in CoRR: arXiv:1107.5538v1 and arXiv:1102.1226v

Security, privacy and trust in wireless mesh networks

With the advent of public key cryptography, digital signature schemes have been extensively studied in order to minimize the signature sizes and to accelerate their execution while providing necessary security properties. Due to the privacy concerns pertaining to the usage of digital signatures in authentication schemes, privacy-preserving signature schemes, which provide anonymity of the signer, have attracted substantial interest in research community. Group signature algorithms, where a group member is able to sign on behalf of the group anonymously, play an important role in many privacy-preserving authentication/ identification schemes. On the other hand, a safeguard is needed to hold users accountable for malicious behavior. To this end, a designated opening/revocation manager is introduced to open a given anonymous signature to reveal the identity of the user. If the identified user is indeed responsible for malicious activities, then s/he can also be revoked by the same entity. A related scheme named direct anonymous attestation is proposed for attesting the legitimacy of a trusted computing platform while maintaining its privacy. This dissertation studies the group signature and direct anonymous attestation schemes and their application to wireless mesh networks comprising resource-constrained embedded devices that are required to communicate securely and be authenticated anonymously, while malicious behavior needs to be traced to its origin. Privacy-aware devices that anonymously connect to wireless mesh networks also need to secure their communication via efficient symmetric key cryptography, as well. In this dissertation, we propose an efficient, anonymous and accountable mutual authentication and key agreement protocol applicable to wireless mesh networks. The proposed scheme can easily be adapted to other wireless networks. The proposed scheme is implemented and simulated using cryptographic libraries and simulators that are widely deployed in academic circles. The implementation and simulation results demonstrate that the proposed scheme is effective, efficient and feasible in the context of hybrid wireless mesh networks, where users can also act as relaying agents. The primary contribution of this thesis is a novel privacy-preserving anonymous authentication scheme consisting of a set of protocols designed to reconcile user privacy and accountability in an efficient and scalable manner in the same framework. The three-party join protocol, where a user can connect anonymously to the wireless mesh network with the help of two semi-trusted parties (comprising the network operator and a third party), is efficient and easily applicable in wireless networks settings. Furthermore, two other protocols, namely two-party identification and revocation protocols enable the network operator, with the help of the semi-trusted third party, to trace suspected malicious behavior back to its origins and revoke users when necessary. The last two protocols can only be executed when the two semi-trusted parties cooperate to provide accountability. Therefore, the scheme is protected against an omni-present authority (e.g. network operator) violating the privacy of network users at will. We also provide arguments and discussions for security and privacy of the proposed scheme

Secure Authentication and Privacy-Preserving Techniques in Vehicular Ad-hoc NETworks (VANETs)

In the last decade, there has been growing interest in Vehicular Ad Hoc NETworks (VANETs). Today car manufacturers have already started to equip vehicles with sophisticated sensors that can provide many assistive features such as front collision avoidance, automatic lane tracking, partial autonomous driving, suggestive lane changing, and so on. Such technological advancements are enabling the adoption of VANETs not only to provide safer and more comfortable driving experience but also provide many other useful services to the driver as well as passengers of a vehicle. However, privacy, authentication and secure message dissemination are some of the main issues that need to be thoroughly addressed and solved for the widespread adoption/deployment of VANETs. Given the importance of these issues, researchers have spent a lot of effort in these areas over the last decade. We present an overview of the following issues that arise in VANETs: privacy, authentication, and secure message dissemination. Then we present a comprehensive review of various solutions proposed in the last 10 years which address these issues. Our survey sheds light on some open issues that need to be addressed in the future

Anonymous, Secure and Efficient Vehicular Communications

Vehicular communication networking is a promising approach for facilitating road safety, traffic management, and infotainment dissemination for drivers and passengers. However, it is subject to various malicious abuses and security attacks which hinder it from practical implementation. In this study, we propose a novel security protocol called GSIS based on group signature and identity-based signature schemes to meet the unique requirements of vehicular communication networks. The proposed protocol not only guarantees security and anonymity, but also provides easy traceability when the identity of the sender of a message has to be revealed by the authority. However, the cryptographic operations introduced in GSIS as well as the existing public key based message authentication protocols incur some computation and communication overhead which affect the system performance. Simulation results show that the GSIS security protocol is only applicable under light traffic conditions in terms of the message end to end delay and message loss ratio. Both the GSIS protocol and the existing public key based security protocols have to sign and verify all the received messages with asymmetric algorithms. The PKI based approach also has to attach a public key certificate in each packet. Therefore, to enhance the system performance and mitigate the message overhead without compromising the security requirement, this study further proposes an enhanced TESLA based Secure Vehicular Communication (TSVC) protocol. In TSVC, the communication overhead can be significantly reduced due to the MAC tag attached in each packet and only a fast hash operation is required to verify each packet. Simulation results show that TSVC maintains acceptable message latency, using a much smaller packet size, and significantly reduces the message loss ratio as compared to GSIS and existing PKI based protocols, especially when the traffic is denser. We conclude that the proposed approach could serve as good candidate for future vehicular communication networks

Authentication and Key Exchange in Mobile Ad Hoc Networks

Over the past decade or so, there has been rapid growth in wireless and mobile applications technologies. More recently, an increasing emphasis has been on the potential of infrastructureless wireless mobile networks that are easy, fast and inexpensive to set up, with the view that such technologies will enable numerous new applications in a wide range of areas. Such networks are commonly referred to as mobile ad hoc networks (MANETs). Exchanging sensitive information over unprotected wireless links with unidentified and untrusted endpoints demand the deployment of security in MANETs. However, lack of infrastructure, mobility and resource constraints of devices, wireless communication links and other unique features of MANETs induce new challenges that make implementing security a very difficult task and require the design of specialized solutions. This thesis is concerned with the design and analysis of security solutions for MANETs. We identify the initial exchange of authentication and key credentials, referred to as pre-authentication, as well as authentication and key exchange as primary security goals. In particular, the problem of pre-authentication has been widely neglected in existing security solutions, even though it is a necessary prerequisite for other security goals. We are the first to classify and analyze different methods of achieving pairwise pre-authentication in MANETs. Out of this investigation, we identify identity-based cryptographic (IBC) schemes as well-suited to secure MANET applications that have no sufficient security solutions at this time. We use pairing-based IBC schemes to design an authentication and key exchange framework that meets the special requirements of MANETs. Our solutions are comprised of algorithms that allow for efficient and secure system set up, pre-authentication, mutual authentication, key establishment, key renewal, key revocation and key escrow prevention. In particular, we present the first fully self-organized key revocation scheme for MANETs that does not require any trusted third party in the network. Our revocation scheme can be used to amend existing IBC solutions, be seamlessly integrated in our security framework and even be adopted to conventional public key solutions for MANETs. Our scheme is based on propagated accusations and once the number of received accusations against a node reaches a defined threshold, the keys of the accused nodes are revoked. All communications are cryptographically protected, but unlike other proposed schemes, do not require computationally demanding digital signatures. Our scheme is the first that efficiently and securely enables nodes to revoke their own keys. Additionally, newly joining nodes can obtain previous accusations without performing computationally demanding operations such as verifying digital signatures. Several security and performance parameters make our scheme adjustable to the hostility of the MANET environment and the degree of resource constraints of network and devices. In our security analysis we show how security parameters can be selected to prevent attacks by colluding nodes and roaming adversaries. In our proposed security framework, we utilize special properties of pairing-based keys to design an efficient and secure method for pairwise pre-authentication and a set of ID-based authenticated key exchange protocols. In addition, we present a format for ID-based public keys that, unlike other proposed formats, allows key renewal before the start of a new expiry interval. Finally, we are the first to discuss the inherent key escrow property of IBC schemes in the context of MANETs. Our analysis shows that some special features of MANETs significantly limit the escrow capabilities of key generation centers (KGCs). We propose a novel concept of spy nodes that can be utilized by KGCs to increase their escrow capabilities and analyze the probabilities of successful escrow attacks with and without spy nodes. In summary, we present a complete authentication and key exchange framework that is tailored for MANET applications that have previously lacked such security solutions. Our solutions can be implemented using any pairing-based IBC scheme. The component design allows for the implementation of single schemes to amend existing solutions that do not provide certain functionalities. The introduction of several security and performance parameters make our solutions adjustable to different levels of resource constraints and security needs. In addition, we present extensions that make our solutions suitable for applications with sporadic infrastructure access as envisioned in the near future

Security in Delay Tolerant Networks

Delay- and Disruption-tolerant wireless networks (DTN), or opportunistic networks, represent a class of networks where continuous end-to-end connectivity may not be possible. DTN is a well recognized area in networking research and has attracted extensive attentions from both network designers and application developers. Applications of this emergent communication paradigm are wide ranging and include sensor networks using scheduled intermittent connectivity, vehicular DTNs for dissemination of location-dependent information (e.g., local ads, traffic reports, parking information, etc.), pocket-switched networks to allow humans to communicate without network infrastructure, and underwater acoustic networks with moderate delays and frequent interruptions due to environmental factors, etc. Security is one of the main barriers to wide-scale deployment of DTNs, but has gained little attention so far. On the one hand, similar to traditional mobile ad hoc networks, the open channel and multi-hop transmission have made DTNs vulnerable to various security threats, such as message modification/injection attack or unauthorized access and utilization of DTN resources. On the other hand, the unique security characteristics of DTNs including: long round-trip delay, frequent disconnectivity, fragmentation, opportunistic routing as well as limited computational and storage capability, make the existing security protocols designed for the conventional ad hoc networks unsuitable for DTNs. Therefore, a series of new security protocols are highly desired to meet stringent security and efficiency requirements for securing DTNs. In this research, we focus on three fundamental security issues in DTNs: efficient DTN message (or bundle) authentication, which is a critical security service for DTN security; incentive issue, which targets at stimulating selfish nodes to forward data for others; and certificate revocation issue, which is an important part of public key management and serves the foundation of any DTN security protocols. We have made the following contributions: First of all, the unique ``store-carry-and-forward'' transmission characteristic of DTNs implies that bundles from distinct/common senders may opportunistically be buffered at some common intermediate nodes. Such a ``buffering'' characteristic distinguishes DTN from any other traditional wireless networks, for which intermediate cache is not supported. To exploit such buffering opportunities, we propose an Opportunistic Batch Bundle Authentication Scheme (OBBA) to dramatically reduce the bundle authentication cost by seamlessly integrating identity-based batch signatures and Merkle tree techniques. Secondly, we propose a secure multi-layer credit based incentive scheme to stimulate bundle forwarding cooperation among DTNs nodes. The proposed scheme can be implemented in a fully distributed manner to thwart various attacks without relying on any tamper-proof hardware. In addition, we introduce several efficiency-optimization techniques to improve the overall efficiency by exploiting the unique characteristics of DTNs. Lastly, we propose a storage-efficient public key certificate validation method. Our proposed scheme exploits the opportunistic propagation to transmit Certificate Revocation List (CRL) list while taking advantage of bloom filter technique to reduce the required buffer size. We also discuss how to take advantage of cooperative checking to minimize false positive rate and storage consumption. For each research issue, detailed simulation results in terms of computational time, transmission overhead and power consumption, are given to validate the efficiency and effectiveness of the proposed security solutions