Physical Layer Wireless Security Made Fast and Channel Independent

There is a growing interest in physical layer security. Recent work has demonstrated that wireless devices can generate a shared secret key by exploiting variations in their channel. The rate at which the secret bits are generated, however, depends heavily on how fast the channel changes. As a result, existing schemes have a low secrecy rate and are mainly applicable to mobile environments. In contrast, this paper presents a new physical-layer approach to secret key generation that is both fast and independent of channel variations. Our approach makes a receiver jam the signal in a manner that still allows it to decode the data, yet prevents other nodes from decoding. Results from a testbed implementation show that our method is significantly faster and more accurate than state of the art physical-layer secret key generation protocols. Specifically, while past work generates up to 44 secret bits/s with a 4% bit disagreement between the two devices, our design has a secrecy rate of 3-18 Kb/s with 0% bit disagreement

iJam: Jamming Oneself for Secure Wireless Communication

Wireless is inherently less secure than wired networks because of its broadcast nature. Attacks that simply snoop on the wireless medium successfully defeat the security of even 802.11 networks using the most recent security standards (WPA2-PSK). In this paper we ask the following question: Can we prevent this kind of eavesdropping from happening? If so, we can potentially defeat the entire class of attacks that rely on snooping. This paper presents iJam, a PHY-layer protocol for OFDM-based wireless systems. iJam ensures that an eavesdropper cannot successfully demodulate a wireless signal not intended for it. To achieve this iJam strategically introduces interference that prevents an eavesdropper from decoding the data, while allowing the intended receiver to decode it. iJam exploits the properties of 802.11â s OFDM signals to ensure that an eavesdropper cannot even tell which parts of the signal are jammed. We implement iJam and evaluate it in a testbed of GNURadios with an 802.11-like physical layer. We show that iJam makes the data bits at the adversary look random, i.e., the BER becomes close to 50%, whereas the receiver can perfectly decode the data

Disjoint difference families and their applications

Difference sets and their generalisations to difference families arise from the study of designs and many other applications. Here we give a brief survey of some of these applications, noting in particular the diverse definitions of difference families and the variations in priorities in constructions. We propose a definition of disjoint difference families that encompasses these variations and allows a comparison of the similarities and disparities. We then focus on two constructions of disjoint difference families arising from frequency hopping sequences and showed that they are in fact the same. We conclude with a discussion of the notion of equivalence for frequency hopping sequences and for disjoint difference families

Secure Communication with a Byzantine Relay

Abstract—We consider a communication scenario where the source and the destination can communicate only via a relay node who is both an eavesdropper and a Byzantine attacker. Hence for secure communication, two requirements must be met simultaneously: the transmitted message must be kept secret, and a Byzantine attack must be detected reliably. Both a discrete noiseless adder model with the relay receiving the real sum of two signals and a Gaussian model are considered. In both models, the loss in rate due to Byzantine detection can be made arbitrarily small. For the discrete adder model, we show that the probability that the adversary wins decreases exponentially with the number of channel uses. For the Gaussian model, we show that this probability decreases exponentially with the square root of the number of channel uses. The rate derived in this paper is the strong secrecy rate, and the rate loss incurred due to the untrusted and Byzantine relay is measured with respect to the achievable secrecy rate when the relay is untrusted but honest. The result is obtained via a careful combination of the algebraic manipulation detection (AMD) code, the linear wiretap code constructed from low density parity check (LDPC) code, randomly generated wire-tap code and for the Gaussian model the lattice code. I