Robust key generation from signal envelopes in wireless networks

Abstract

The broadcast nature of a wireless link provides a natural eavesdropping and intervention capability to an adversary. Thus, securing a wireless link is essential to the security of a wireless network, and key generation algorithms are necessary for securing wireless links. However, traditional key agreement algorithms can be very costly in many settings, e.g. in wireless ad-hoc networks, since they consume scarce resources such as bandwidth and battery power.Traditional key agreement algorithms are not suitable for wireless ad-hoc networks since they consume scarce resources such as bandwidth and battery power. This paper presents a novel approach that couples the physical layer characteristics of wireless networks with key generation algorithms. It is based on the wireless communication phenomenon known as the principle of reciprocity which states that in the absence of interference both transmitter and receiver experience the same signal envelope. The key-observation here is that the signal envelope information can provide to the two transceivers two correlated random sources that provide sufficient amounts of entropy which can be used to extract a cryptographic key. In contrast, it is virtually impossible for a third party, which is not located at one of the transceiver's position, to obtain or * This work was done in part while the author was with Rensselaer Polytechnic Institute.Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. To copy otherwise, to republish, to post on servers or to redistribute to lists, requires prior specific permission and/or a fee. predict the exact envelope; thus retrieve the key. Since in the presence of interference strict reciprocity property can not be maintained; our methodology is based on detecting deep fades to extract correlated bitstrings. In particular, we show how a pair of transceivers can reconcile such bitstrings and finally flatten their distribution to reach key agreement. In our constructions we use cryptographic tools related to randomness extraction and information reconciliation. We introduce "secure fuzzy information reconciliators" a tool that enables us to describe robust key generation systems in our setting. Finally we provide a computational study that presents a simulation of a wireless channel that demonstrates the feasibility of our approach and justifies the assumptions made in our analysis.

An Adaptive Quantization Algorithm for Secret Key Generation Using Radio Channel Measurements

“…A scheme for generating periodically secret keys based on deep fades has been proposed in [4]. This work requires frequent fluctuations on channel to create secret keys.…”

Secret Key Generation Rate vs. Reconciliation Cost Using Wireless Channel Characteristics in Body Area Networks

“…Existing research in this domain, has primarily focussed on using this component, i.e. channel variation, for key generation purposes [3] [5]. The slow component has not been identified and studied as such because application scenarios in the literature have not focussed on distance variation and line of sight between communicating parties but specifically on motion itself.…”

“…Different channel characteristics have been considered for this purpose in the literature, including radio signal strength [3] [4], signal envelope [5] and signal phase [6]. We specifically use the received signal strength (RSS) because it is the most convenient to measure for most small devices.…”

The generation of shared cryptographic keys through channel impulse response estimation at 60 GHz.

“…In [15], the authors present a MIMO system with two antennas per node which generates bits for a keying variable based on which antenna receives the stronger signal. In [16], threshold detection of deep fades in signal strength is measured in time.…”

“…In previously published work, metrics with nonlinear distributions and a static threshold yield key bits that are not equally distributed [16]. It is to emphasize the importance of conditioning that metrics and weights are defined separately.…”