Recently, Shen, Shi, and Waters introduced the notion of predicate privacy, and proposed a scheme that achieves predicate privacy in the symmetric-key settings. In this paper, we propose two schemes. In the first scheme, we extend PEKS to support predicate privacy based on the idea of randomization. To the best of our knowledge, this is the first work that ensures predicate privacy in the public-key settings without requiring interactions between the receiver and potential senders, the size of which may be very large. Moreover, we identify a new type of attacks against PEKS, i.e., statistical guessing attacks. Accordingly, we introduce a new notion called statistics privacy, i.e., the property that predicate privacy is preserved even when the statistical distribution of keywords is known. The second scheme we proposed makes a tradeoff between statistics privacy and storage efficiency (of the delegate). Compared to PEKS, both schemes introduce reasonable communication and computation overheads and can be smoothly deployed in existing systems.

Abstract Although extensive research work has been undertaken to secure mobilead hocnetworks, till recently, researchers began to pay attention to the anonymity issue, and this issue was investigated mainly in terms of secure routing and data forwarding. We indicate that, in mobilead hocnetworks, there is an increasing interest in providing anonymity for the witnesses, i.e., those users who share their knowledge in detecting either malicious or selfish users. On the other hand, it is also a challenging problem to prevent the misuse of anonymous sources. In this paper, we propose thePlainClothesMan(PCM) protocol to provide anonymity for the witness who helps identify malicious or selfish users. Once there are more than a certain number of claims from distinct users against the same user, she is identified as a malicious or selfish user. Moreover, in PCM, the misuse of the witness anonymity is prevented in such a way that any malicious user who broadcasts multiple invalid claims against the same user for the same reason can be identified. Two exemplary scenarios are designed and simulated to model the necessities of witness anonymity in mobilead hocnetworks. Simulation results show that witness anonymity is very important for ensuring proper and efficient executions of fundamental functionalities of mobilead hocnetworks, e.g., certificate revocation and fairness, and PCM is both effective and efficient in providing such a type of anonymity. Copyright © 2009 John Wiley & Sons, Ltd.

In this paper, we introduce the concept ofwitness anonymityfor peer-to-peer systems, as well as other systems with the peer-to-peer nature. Witness anonymity combines the seemingly conflicting requirements of anonymity (for honest peers who report on the misbehavior of other peers) and accountability (for malicious peers that attempt to misuse the anonymity feature to slander honest peers). We propose theSecure Deep Throat(SDT) protocol to provide anonymity for the witnesses of malicious or selfish behavior to enable such peers to report on this behavior without fear of retaliation. On the other hand, in SDT, the misuse of anonymity is restrained in such a way that any malicious peer attempting to send multiple claims against the same innocent peer for the same reason (i.e., the same misbehavior type) can be identified. We also describe how SDT can be used in two modes. The active mode can be used in scenarios with real-time requirements, e.g., detecting and preventing the propagation of peer-to-peer worms, whereas the passive mode is suitable for scenarios without strict real-time requirements, e.g., query-based reputation systems. We analyze the security and overhead of SDT, and present countermeasures that can be used to mitigate various attacks on the protocol. Moreover, we show how SDT can be easily integrated with existing protocols/mechanisms with a few examples. Our analysis shows that the communication, storage, and computation overheads of SDT are acceptable in peer-to-peer systems.

Due to the poor physical protection of sensor nodes, it is generally assumed that an adversary can capture and compromise a small number of sensors in the network. In a node replication attack, an adversary can take advantage of the credentials of a compromised node to surreptitiously introduce replicas of that node into the network. Without an effective and efficient detection mechanism, these replicas can be used to launch a variety of attacks that undermine many sensor applications and protocols. In this paper, we present a novel distributed approach called Localized Multicast for detecting node replication attacks. The efficiency and security of our approach are evaluated both theoretically and via simulation. Our results show that, compared to previous distributed approaches proposed by Parno et al., Localized Multicast is more efficient in terms of communication and memory costs in large-scale sensor networks, and at the same time achieves a higher probability of detecting node replicas.

As a combination of ad hoc networks and wireless local area network (WLAN), the wireless mesh network (WMN) provides a low-cost convenient solution to the last-mile network-connectivity problem. As such, existing route protocols designed to provide security and privacy protection for ad hoc networks are no longer applicable in WMNs. On the other hand, little research has focused on privacy-preserving routing for WMNs. In this paper, we propose two solutions for security and privacy protection in WMNs. The first scheme relies on group signatures, together with user credentials, to deliver security and privacy protection. By enforcing access control using user credentials, the user's identity has to be disclosed to mesh routers. To avoid this, our second scheme employs pairwise secrets between any two users to achieve stronger privacy protection. In the second scheme, the user is kept anonymous to mesh routers. Finally, we analyze these two schemes in terms of security, privacy, and performance.

Wireless sensor nodes lack hardware support for tamper- resistance and are often deployed in unattended environments, thus leaving them vulnerable to capture and compromise by an adversary. In a node replication attack, an adversary uses the credentials of a compromised node to surreptitiously introduce replicas of that node into the network. These replicas are then used to launch a variety of attacks that subvert the goal of the sensor application, and the operation of the underlying protocols. We present a novel distributed approach called Localized Multicast for detecting node replication attacks. We evaluate the performance and security of our approach both theoretically and via simulation. Our results show that Localized Multicast is more efficient than previous distributed approaches in terms of communication and memory costs. Further, in our approach, the probability of detecting node replicas is much higher than that achieved in previous distributed protocols.

In this paper, we introduce the concept of witness anonymity for peer-to-peer systems. Witness anonymity combines the seemingly conflicting requirements of anonymity (for honest peers who report on the misbehavior of other peers) and accountability (for malicious peers that attempt to misuse the anonymity feature to slander honest peers). We propose the Secure Deep Throat (SDT) protocol to provide anonymity for witnesses of malicious or selfish behavior to enable such peers to report on this behavior without fear of retaliation. On the other hand, in SDT the misuse of anonymity is restrained in such a way that any malicious peer that attempts to send multiple claims against the same innocent peer for the same reason (i.e., the same misbehavior type) can be identified. We also describe how SDT can be used in two modes. The active mode can be used in scenarios with real-time requirements, e.g., detecting and preventing the propagation of peer-to-peer worms, whereas the passive mode is suitable for scenarios without strict real-time requirements, e.g., query-based reputation systems. We analyze the security and overhead of SDT and present countermeasures that can be used to mitigate various attacks on the protocol. Our analysis shows that the communication, storage, and computation overheads of SDT are acceptable in peer-to-peer systems.

In this paper, we first define the requirements on anonymity and security properties of the routing protocol in mobile ad hoc networks, and then propose a new anonymous routing protocol with the local-repair mechanism. Detailed analysis shows that our protocol achieves both anonymity and security properties defined. A major challenge in designing anonymous routing protocols is to reduce computation and communication costs. To overcome this challenge, our protocol is design to require neither asymmetric nor symmetric encryption/decryption while updating the flooding route requests; more importantly, once a route is broken, instead of re-launching a new costly flooding route discovery process like previous work, our protocol provides a local-repair mechanism to fix broken parts of a route without compromising anonymity

In this paper, we propose a highly efficient key agreement scheme based on a novel key tree construction for ad hoc networks. The key tree is constructed taking into consideration of the multicast tree which represents the underlying network topology. Our scheme greatly reduces the communications and computation cost for group key agreement and has high flexibility in having dynamic group memberships. We implement our scheme in ns-2 and evaluate its performance in terms of overhead and communication cost. The simulation results show that our scheme enjoys great advantages over other schemes in the literature

Most of previous research work in key management can only resist passive attacks, such as dropping the certificate request, and are vulnerable under active attacks, such as returning a fake reply to the node requesting the certification service. In this paper, we propose two algorithms to address both security and efficiency issues of certification services in ad hoc networks. Both of the algorithms can resist active attacks. In addition, simulation results show that, compared to the previous works, our second algorithm is not only much faster in a friendly environment, but it also works well in a hostile environment in which existing schemes work poorly. Furthermore, the process of generating partial certificates in our second algorithm is extremely fast. Such advantage is critical in ad hoc networks where by nature the less help a node requests from its neighbors, the higher is the chance of obtaining the help. Consequently, using our second algorithm, a node can easily find enough neighboring nodes which provide the certification service.

In this paper, we review a PKC (public key cryptosystem) based protocol, referred to as the Stanford protocol, aimed at overcoming several security deficiencies in IEEE 802.1X and to provide access control in both wireless and wired networks. One main objective of the Stanford protocol is to provide DoS resistance for the wireless network. Meanwhile, in the wireless environment, identity confidentiality of the mobile user is especially important since the disclosed identity could be used to locate the user and track his movement. But our analysis shows that the Stanford protocol fails to fulfill these requirements. So we propose a new PKC-based protocol that not only provides DoS resistance and perfect forward secrecy, but also provides identity anonymity for the clients. We also present detailed security and performance analysis for our protocol, and show that our protocol is secure and efficient for access control in wireless networks.

Although there are a large number of papers on secure routing in mobile ad-hoc networks, only a few consider the anonymity issue. We define more strict requirements on the anonymity and security properties of the routing protocol, and notice that previous research works only provide weak location privacy and route anonymity, and are vulnerable to specific attacks. Therefore, we propose the anonymous secure routing (ASR) protocol that can provide additional properties on anonymity, i.e. identity anonymity and strong location privacy, and at the same time ensure the security of discovered routes against various passive and active attacks. Detailed analysis shows that ASR can achieve both anonymity and security properties, as defined in the requirements, of the routing protocol in mobile ad-hoc networks.