Restricting network access of routing and packet forwarding to well-behaving nodes, and denying access from misbehaving nodes are critical for the proper functioning of a mobile ad-hoc network where cooperation among all networking nodes is usually assumed. However, the lack of a network infrastructure, the dynamics of the network topology and node membership, and the potential attacks from inside the network by malicious and/or non-cooperative selfish nodes make the conventional network access control mechanisms not applicable. We present URSA, a ubiquitous and robust access control solution for mobile ad-hoc networks. URSA implements ticket certification services through multiple-node consensus and fully localized instantiation, and uses tickets to identify and grant network access to well-behaving nodes. In URSA, no single node monopolizes the access decision or is completely trusted, and multiple nodes jointly monitor a local node and certify/revoke its ticket. Furthermore, URSA ticket certification services are fully localized into each node's neighborhood to ensure service ubiquity and resilience. Through analysis, simulations and experiments, we show that our design effectively enforces access control in the highly dynamic, mobile ad-hoc network.

Combining effective security and usability is often considered impossible. For example, deploying effective security for wireless networks is a difficult task, even for skilled systems administrators -- a fact that is impeding the deployment of many mobile systems.

The 802.11 encryption standard Wired Equivalent Privacy (WEP) is still widely used today despite the numerous discussions on its insecurity. In this paper, we present a novel vulnerability which allows an attacker to send arbitrary data on a WEP network after having eavesdropped a single data packet. Furthermore, we present techniques for real-time decryption of data packets, which may be used under common circumstances. Vendor produced mitigation techniques which cause frequent WEP re-keying prevent traditional attacks, whereas our attack remains effective even in such scenarios. We implemented a fully automatic version of this attack which demonstrates its practicality and feasibility in real networks. As even rapidly re-keyed networks can be quickly compromised, we believe WEP must now be abandoned rather than patched yet again. 1.

The majority of attacks made upon modern computers have been successful due to the exploitation of the same errors and weaknesses that have plagued computer systems for the last thirty years. Because the industry has not learned from these mistakes, new protocols and systems are not designed with the aspect of security in mind; and security that is present is typically added as an afterthought. What makes these systems so vulnerable is that the security design process is based upon assumptions that have been made in the past; assumptions which now have become obsolete or irrelevant. In addition, fundamental errors in the design and implementation of systems repeatedly occur, which lead to failures. This

Vaudenay recently demonstrated side-channel attacks on a common encryption scheme, CBC Mode encryption, exploiting a \valid padding" oracle [Vau02]. Mirroring the side-channel attacks of Bleichenbacher [Ble98] and Manger [Man01] on asymmetric schemes, he showed that symmetric encryption methods are just as vulnerable to side-channel weaknesses when an adversary is able to distinguish between valid and invalid ciphertexts.

Abstract. Wireless networking has the power to t the Internet with wings, however, it will not take o until the security technological hurdles have been overcome. In this paper we propose a very e cient and provably-secure group key agreement well suited for unbalanced networks consisting of devices with strict power consumption restrictions and wireless gateways with less stringent restrictions. Our method meets practicability, simplicity, and strong notions of security. 1

Preventing execution of unauthorized software on a given computer plays a pivotal role in system security. The key problem is that although a program at the beginning of its execution can be verified as authentic, while running, its execution flow can be redirected to externally injected malicious code using, for example, a bu#er overflow exploit. Existing techniques address this problem by trying to detect the intrusion at run-time or by formally verifying that the software is not prone to a particular attack. We take a

this article. Problems With WEP WEP has several serious inherent problems. It does not meet its fundamental goals of wired-equivalent confidentiality. It also fails to meet the expected goals for integrity and authentication

Abstract. Password-based key exchange schemes are designed to provide entities communicating over a public network, and sharing a (short) password only, with a session key (e.g, the key is used for data integrity and/or confidentiality). The focus of the present paper is on the analysis of very efficient schemes that have been proposed to the IEEE P1363 Standard working group on password-based authenticated key-exchange methods, but for which actual security was an open problem. We analyze the AuthA key exchange scheme and give a complete proof of its security. Our analysis shows that the AuthA protocol and its multiple modes of operation are provably secure under the computational Diffie-Hellman intractability assumption, in both the random-oracle and the ideal-cipher models. 1

In recent years, wireless Internet service providers (WISPs) have established Wi-Fi hotspots in increasing numbers at public venues, providing local coverage to traveling users and empowering them with the ability to access email, Web, and other Internet applications on the move. In this paper, we observe that while the mobile computing landscape has changed both in terms of number and type of hotspot venues, there are several technological and deployment challenges remaining before hotspots can become an ubiquitous infrastructure. These challenges include authentication, security, coverage, management, location services, billing, and interoperability. We discuss existing research, the work of standards bodies, and the experience of commercial hotspot providers in these areas, and then describe compelling open research questions that remain.