With the growing prevalence of sensor and wireless networks comes a new demand for location-based access control mechanisms. We introduce the concept of secure location verification, and we show how it can be used for location-based access control. Then, we present the Echo protocol, a simple method for secure location verification. The Echo protocol is extremely lightweight: it does not require time synchronization, cryptography, or very precise clocks. Hence, we believe that it is well suited for use in small, cheap, mobile devices.

In an ad hoc network, mobile computers (or nodes) cooperate to forward packets for each other, allowing nodes to communicate beyond their direct wireless transmission range. Many proposed routing protocols for ad hoc networks operate in an on-demand fashion, as on-demand routing protocols have been shown to often have lower overhead and faster reaction time than other types of routing based on periodic (proactive) mechanisms. Significant attention recently has been devoted to developing secure routing protocols for ad hoc networks, including a number of secure ondemand routing protocols, that defend against a variety of possible attacks on network routing. In this paper, we present the rushing attack, a new attack that results in denial-of-service when used against all previous on-demand ad hoc network routing protocols. For example, DSR, AODV, and secure protocols based on them, such as Ariadne, ARAN, and SAODV, are unable to discover routes longer than two hops when subject to this attack. This attack is also particularly damaging because it can be performed by a relatively weak attacker. We analyze why previous protocols fail under this attack. We then develop Rushing Attack Prevention (RAP),a generic defense against the rushing attack for on-demand protocols. RAP incurs no cost unless the underlying protocol fails to find a working route, and it provides provable security properties even against the strongest rushing attackers.

Current mechanisms for authenticating communication between devices that share no prior context are inconvenient for ordinary users, without the assistance of a trusted authority. We present and analyze Seeing-Is-Believing, a system that utilizes 2D barcodes and cameraphones to implement a visual channel for authentication and demonstrative identification of devices. We apply this visual channel to several problems in computer security, including authenticated key exchange between devices that share no prior context, establishment of a trusted path for configuration of a TCG-compliant computing platform, and secure device configuration in the context of a smart home. 1.

An emerging class of important applications uses ad hoc wireless networks' of low-power sensor devices to monitor and send information about a possibly hostile environment to a powerful base station connected to a wired network. To conserve power, intermediate network nodes should aggregate results' from individual sensors'. However, this opens the risk that a single compromised sensor device can render the network useless, or worse, mislead the operator into trusting a false reading. We present a protocol that provides a secure aggregation mechanism for wireless networks' that is resilient to both intruder devices and single device key compromises. Our protocol is designed to work within the computation, memory and power consumption limits' of inexpensive sensor devices', but takes advantage of the properties of wireless networking, as well as the power asymmetry between the devices and the base station.

In this paper we present SECTOR, a set of mechanisms for the secure verification of the time of encounters between nodes in multi-hop wireless networks. This information can be used notably to prevent wormhole attacks (without requiring any clock synchronization), to secure routing protocols based on last encounters (with only loose clock synchronization) , and to control the topology of the network. SECTOR is based primarily on distance-bounding techniques, on one-way hash chains and on Merkle hash trees. We analyze the communication, computation and storage complexity of the proposed mechanisms and we show that, due to their efficiency and simplicity, they are compliant with the limited resources of most mobile devices.

In order to meet performance goals, it is widely agreed that vehicular ad hoc networks (VANETs) must rely heavily on node-to-node communication, thus allowing for malicious data traffic. At the same time, the easy access to information afforded by VANETs potentially enables the difficult security goal of data validation. We propose a general approach to evaluating the validity of VANET data. In our approach a node searches for possible explanations for the data it has collected based on the fact that malicious nodes may be present. Explanations that are consistent with the node’s model of the VANET are scored and the node accepts the data as dictated by the highest scoring explanations. Our techniques for generating and scoring explanations rely on two assumptions: 1) nodes can tell “at least some ” other nodes apart from one another and 2) a parsimony argument accurately reflects adversarial behavior in a VANET. We justify both assumptions and demonstrate our approach on specific VANETs.

Contrary to the common belief that mobility makes security more difficult to achieve, we show that node mobility can, in fact, be useful to provide security in ad hoc networks. We propose a technique in which security associations between nodes are established, when they are in the vicinity of each other, by exchanging appropriate cryptographic material. We show that this technique is generic, by explaining its application to fully self-organized ad hoc networks and to ad hoc networks placed under an (off-line) authority. We also propose an extension of this basic mechanism, in which a security association can be established with the help of a "friend". We show that our mechanism can work in any network configuration and that the time necessary to set up the security associations is strongly influenced by several factors, including the size of the deployment area, the mobility patterns, and the number of friends; we provide a detailed investigation of this influence.

Authentication of communication channels between devices that lack any previous association is an challenging problem. It has been considered in many contexts and in various flavors, most recently, by McCune et al., where human-assisted device authentication is achieved through the use of photo cameras (present in some cellphones) and 2-dimensional barcodes. Their proposed Seeing-is-Believing system allows users with devices equipped with cameras to use the visual channel for authentication of unfamiliar devices, so as to defeat man-inthe-middle attacks. In this paper, we investigate an alternative and complementary approach—the use of the audio channel for humanassisted authentication of previously un-associated devices. Our motivation is three-fold: (1) many personal devices are not equipped with cameras or scanners, (2) some human users are visually impaired (hence, cannot be in the authentication pipeline of a vision-based system), and (3) some usage scenarios preclude either taking a sufficiently clear picture and/or the use of barcodes. We develop and evaluate a system we call Loud-and-Clear (L&C) authentication, which, like Seeing-is-Believing, places little demand on the human user. The L&C system is based on the use of a text-to-speech engine to read an auditoriallyrobust, grammatically-correct pass-phrase derived from an authentication string that is to be used by peer devices. In particular, by coupling the auditory reading of the one-way hash of an authentication string on one device with the display of of this text on another device, we demonstrate that L&C is suitable for secure device pairing (e.g., key exchange) and similar tasks. We also describe several use cases, as well as provide some performance data for a prototype implementation and a discussion of the security properties of L&C. 1

We propose a way to establish peer-to-peer authenticated communications over an insecure channel by using an extra channel which can authenticate very short strings, e.g. 15 bits. We call this SAS-based authentication as for authentication based on Short Authenticated Strings. The extra channel uses a weak notion of authentication in which strings cannot be forged nor modified, but whose delivery can be maliciously stalled, canceled, or replayed. Our protocol is optimal and relies on an extractable or equivocable commitment scheme. This approach offers an alternative (or complement) to public-key infrastructures, since we no longer need any central authority, and to password-based authenticated key exchange, since we no longer need to establish a confidential password. It can be used to establish secure associations in ad-hoc networks. Applications could be the authentication of a public key (e.g. for SSH or PGP) by users over the telephone, the user-aided pairing of wireless (e.g. Bluetooth) devices, or the restore of secure associations in a disaster case, namely when one remote peer had his long-term keys corrupted.

Ubiquitous and mobile technologies create new challenges for system security. Effective security solutions depend not only on the mathematical and technical properties of those solutions, but also on people’s ability to understand them and use them as part of their work. As a step towards solving this problem, we have been examining how people experience security as a facet of their daily life, and how they routinely answer the question, “is this system secure enough for what I want to do?” We present a number of findings concerning the scope of security, attitudes towards security, and the social and organizational contexts within which security concerns arise, and point towards emerging technical solutions.