Localization techniques that allow inferring the location of wireless devices directly from received signals have exposed mobile users to new threats. Adversaries can easily collect required information (such as signal strength) from target users, however, techniques securing location information at the physical layer of the wireless communication systems have not received much attention. In this paper, we propose Phantom, a novel approach to allow mobile devices thwart unauthorized adversary's location tracking by creating forged locations. In particular, Phantom leverages cooperation among multiple mobile devices in close vicinity and utilizes synchronized transmissions among those nodes to obfuscate localization efforts of adversary systems. Through an implementation on software-defined radios (GNU Radios) and extensive simulation with real location traces, we see that Phantom can improve location privacy.

Antenna diversity is a well-known technique used to improve the quality and reliability of a wireless link. In vehicular networks, a different approach to antenna diversity is needed due to their unique channel characteristics. However, this issue has not been actively researched, especially for the positioning of antennas. In this paper, we highlight the benefit of vertical diversity over traditional horizontal diversity techniques in vehicular network environments. Through experiments using IEEE 802.11a radios in the 5.2GHz band, we first show the difference of attenuation patterns from various antenna positions installed in a vehicle, then we show the benefit of vertical diversity by quantifying the diversity gains and combined error rates. This finding has implications for the future position of antenna installation in vehicles.

We design, implement, and evaluate a technique to identify the source network interface card (NIC) of an IEEE 802.11 frame through passive radio-frequency analysis. This technique, called PARADIS, leverages minute imperfections of transmitter hardware that are acquired at manufacture and are present even in otherwise identical NICs. These imperfections are transmitter-specific and manifest themselves as artifacts of the emitted signals. In PARADIS, we measure differentiating artifacts of individual wireless frames in the modulation domain, apply suitable machine-learning classification tools to achieve significantly higher degrees of NIC identification accuracy than prior best known schemes.

This paper analyzes the scalability of message flooding protocols in networks with various node densities, which can be expected in vehicular scenarios. Vehicle safety applications require reliable delivery of warning messages to nearby and approaching vehicles. Due to potentially large distances and shadowing, the delivery protocol must forward messages over multiple hops, thereby increasing network congestion and packet collisions. In addition to application-layer backoff delay and duplicate message suppression mechanisms, location-based backoff techniques have been proposed for vehicular networks. We propose a new hybrid method of location-based and counter-based method, and study several variants through simulations. Our preliminary results in the various density scenarios indicate that the proposed hybrid methods outperform conventional backoff delay techniques and adaptively operate in extremely congested network condition

The efficient computation of the arithmetic operations in finite fields is closely related to the particular ways in which the field elements are presented. The common field representations are a polynomial basis representation and a normal basis representation. In this paper, we introduce a nonconventional basis and present a new bit-parallel multiplier which is as efficient as the modified Massey-Omura multiplier using the type I optimal normal basis.

It is well-known that a class of finite fields GF(2/sup n/) using an optimal normal basis is most suitable for a hardware implementation of arithmetic in finite fields. In this paper, we introduce composite fields of some hardware-applicable properties resulting from the normal basis representation and the optimal condition. We also present a hardware architecture of the proposed composite fields including a bit-parallel multiplier.