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arXiv:2304.10312 · IEEE Communications Letters

Secret-Key-Agreement Advantage Distillation With Quantization Correction

Francesco Ardizzon, Francesco Giurisato, Stefano Tomasin

Published Aug 1, 2023• 7 citations
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Abstract

We consider a physical layer-based secret-key-agreement (SKA) scenario where Alice and Bob aim at extracting a common bit sequence, which should remain secret to Eve, by quantizing a random number obtained from measurements of their communication channel. We propose an asymmetric advantage distillation protocol where i) Alice quantizes her measurement and sends partial information on it over an authenticated public side channel, and ii) Bob (and Eve) quantizes his measurement by exploiting the partial information. The partial information on the position of the measurement in the quantization interval allows Bob to obtain a quantized value closer to that of Alice. Such strategies are shown to increase the lower bound of the secret key rate.

DOI
10.1109/lcomm.2023.3300462

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We consider a physical layer-based secret-key-agreement (SKA) scenario where Alice and Bob aim at extracting a common bit sequence, which should remain secret to Eve, by quantizing a random number obtained from measurements of their communication channel. We propose an asymmetric advantage distillation protocol where i) Alice quantizes her measurement and sends partial information on it over an authenticated public side channel, and ii) Bob (and Eve) quantizes his measurement by exploiting the partial information. The partial information on the position of the measurement in the quantization interval allows Bob to obtain a quantized value closer to that of Alice. Such strategies are shown to increase the lower bound of the secret key rate.
Many military and civil applications using underwater acoustic channels (UWACs) are paired with security services, providing, for instance, secrecy and authenticity to the communication.These mechanisms however often require periodically renewed symmetric keys among two communicating devices, namely Alice and Bob.To this end, secret keys can be agreed upon using the physicallayer communication channel, leveraging, in particular, the reciprocity and randomness of the UWAC to extract a common key that remains secret to an attacker (Eve).In this paper, we propose a novel solution for the advantagedistillation part of the secret key generation procedure.After channel probing, the advantage of distillation lets Alice and Bob extract a sequence of bits from their own (analog) measurements.We propose an asymmetric advantage-distillation protocol with two novel features: i) the quantizers used by Alice and Bob are derived maximizing the secret key capacity cooperating through a public channel and ii) Alice transmits a correction over a public authenticated side channel.Numerical results prove the effectiveness of our approach, showing that exchanging a few bits of information before information reconciliation allows extracting more secret bits from the channel.
Abstract The novel advantage distillation (AD) scheme for secret key agreement (SKA) scheme over relay communication system for the wiretap channel model is proposed. For the case where there are noiseless both the main channel and the eavesdropper’s channel, the SKA scheme for the noiseless relay communication (SKA-NRC) system is proposed. In this scheme, random sequences qA and qB are used as artificial interference to prevent eavesdropping. Simulation results show that with the proposed SKA schemes, the bit error ratio (BER) of eavesdropper Eve maintains stably at 0.5, while legitimate users Alice and Bob are able to get much lower BERs.
In this paper we propose novel advantage distillation and reconciliation approaches for secret key agreement (SKA) over additive white Gaussian noise (AWGN) (possibly fading) channels, using binary phase shift keying (BPSK) constellations. For advantage distillation Bob selects bits having an absolute log-likelihood ratio (LLR) larger than some threshold. For reconciliation, Alice transmits the syndrome of the selected bits with respect to a globally pre-shared forward error correcting (FEC) code. We show that the syndrome transmission does not diminish the advantage of Bob over Eve on the key knowledge, thus being an efficient solution. For the proposed scheme we derive both a lower bound on the achievable secret key rate with ideal wiretap coding, and the effective throughput achieved by using practical codes.
Underwater acoustic communications (UWACs) are being adopted in several applications, and their security mechanisms require periodically renewed symmetric keys among legitimate devices. To this end, a secret key agreement (SKA) exploiting the UWAC context can be implemented. In this paper, we focus on one step of the source-based SKA protocol, i.e., the advantage distillation, when the legitimate users pre-process the channel measurement to increase the agreement while decreasing the attacker's knowledge about the key. We propose to learn the advantage distillation process by using a dataset of observed channels from the legitimate parties and the attacker, respectively. In turn, also the attacker uses such data to extract the key from its own underwater channel observations. The key extraction functions are derived through a computationally efficient data-driven adversarial strategy based on a metric related to the secret key rate that can be computed with a lower computational cost. The proposed strategy is tested considering experimental UWAC data, derived from a sea experiment. Results prove the quick convergence of the algorithm and the advantage of using the proposed techniques.
We consider the distillation phase of the secret key agreement (SKA) channel model for users connected through parallel additive white Gaussian noise fading channels. Alice sends binary phase shift keying modulated random bits to Bob who selects the subset of bits that have a log-likelihood ratio higher than a given threshold, i.e., they are sufficiently reliable. Alice has either full or partial channel state information (CSI) on her channel to the eavesdropper Eve. The main contributions of this paper are: 1) the derivation of the expression of outage probability when partial CSI is available; 2) the introduction of (outage) secret key throughput (SKT) as a metric in the full (partial) CSI scenario; 3) the derivation of SKT bounds; 4) the proposal of a new power allocation and threshold choice algorithm that maximizes the SKT under an outage probability constraint; and 5) the derivation of a suboptimal version of the allocation algorithm amenable for practical implementation obtained by approximating the objective functions with a closed-form expression. Moreover, we show that when power allocation and thresholds are optimized, per-channel and joint SKA are equivalent.
Secret key agreement (SKA) is a basic cryptographic primitive that establishes a shared secret key between parties. In the two-party source model of SKA, Alice and Bob want to share a secret key. They each have private samples of two correlated variables that are partially leaked to Eve. In a one-way SKA protocol, Alice sends a single message to Bob over a public channel, allowing the two parties to calculate a shared secret key that will be essentially unknown to Eve. The length of the key is a function of the number of samplesnnn. In this paper, we prove a tight second-order asymptotic approximation of the key length of one-way SKA protocols, and propose an approach to construct a computationally efficient one-way SKA protocol with near-optimum finite key length. We compare our results with related work, and discuss future research directions.