Efficient High-Rate Secret Key Extraction in Wireless Sensor Networks Using Collaboration

Abstract

Secret key establishment is a fundamental requirement for private communication between two entities. In this article, we propose and evaluate a new approach for secret key extraction where multiple sensors collaborate in exchanging probe packets and collecting channel measurements. Essentially, measurements from multiple channels have a substantially higher differential entropy compared to the measurements from a single channel, thereby resulting in more randomness in the information source for key extraction, and this in turn produces stronger secret keys. We also explore the fundamental trade-off between the quadratic increase in the number of measurements of the channels due to multiple nodes per group versus a linear reduction in the sampling rate and a linear increase in the time gap between bidirectional measurements. To experimentally evaluate collaborative secret key extraction in wireless sensor networks, we first build a simple yet flexible testbed with multiple TelosB sensor nodes. Next, we perform large-scale experiments with different configurations of collaboration. Our experiments show that in comparison to the 1 × 1 configuration, collaboration among sensor nodes significantly increases the secret bit extraction per second, per probe, as well as per millijoule of transmission energy. In addition, we show that the collaborating nodes can improve the performance further when they exploit both space and frequency diversities.

Physical layer secret-key generation with discreet cosine transform for the Internet of Things

“…Thus the sequences of zeros and ones that Alice and Bob create might have some discrepancies. These are reconciled, either through some form of error correction [5], [15] or through some reconciliation protocol like Cascade [12]. There are also some cases where the scheme sacrifices entropy and randomness to result in two sequences that are completely similar after quantization, as seen in [16].…”

Secure Wireless Key Establishment Using Retrodirective Array

“…Since X is publicly known to every node in the system, Bob is able to obtain the waveform observation K b , which in the frequency domain for the purpose of secret key extraction is shown in (9).…”

“…It is noted that G 3 · W * {a,b } • H 2 and H 2 · W * {a,b } • G 3 are equivalent. The noise terms, i.e., the last two terms in both (9) and (11), reduce the correlation coefficients between K a and K b , and hence limit the achievable secret key rates of the proposed system. These aspects are investigated in Section IV.…”

“…There are several characteristics of wireless channels that can be utilized to extract secret keys, such as received signal strength (RSS) [9], channel phase delays [10], multipath relative time delays [11], and full channel state information (CSI) [12]. These parameters are available in network interface cards or customized hardware platforms, therefore many practical key generation systems have been reported [7].…”

“…KGR describes the amount of key bits generated per time unit, and KDR denotes bit disagreement rates of the generated keys shared by legitimate nodes. In [9], [13] multiple nodes or multiple antennas at each node are exploited in order to create multiple usable common channels from which more key bits can be extracted within one channel coherence time period. Similarly, multiple independent or quasi-independent channels can be generated using frequency resources, such as channel hopping in [14], and OFDM signals in [12].…”