IEEE photonics journal

Atmospheric Turbulence-Controlled Cryptosystems

Ivan B. Djordjević

Published Jan 22, 2021• 9 citations

Abstract

To overcome the limitations of QKD, post-quantum cryptography, and computational security-based cryptography protocols in this paper, an atmospheric turbulence-controlled cryptosystem is proposed. The proposed encryption scheme employs the traditional scheme to utilize the atmospheric turbulence as the common source of randomness only in the initialization stage to determine the common parameters to be used in the proposed encryption scheme. To overcome low secret-key rates of traditional scheme, dictated by the long coherence time Tc of turbulence channel, the proposed encryption scheme updates the parameters of gamma-gamma distribution, used to generate irradiance samples for cumulative distribution function-based determination of the key, every Tc seconds and as such the final key is shaped by the atmospheric turbulence channel. We also describe a scheme that randomly selects one of several available paths in which the simultaneously measured irradiance samples, after interleaving, are used to generate the raw key. The secret-key rates of the proposed schemes are orders of magnitude higher compared to corresponding traditional QKD and source type physical-layer security schemes and are comparable with the state-of-the-art optical communication data rates.

DOI: 10.1109/jphot.2021.3053860

Related papers

On the Atmospheric Turbulence-Based Cryptosystems With High Secret-Key Rate

Ivan B. Djordjević

In our recent paper, we proposed using the atmospheric turbulent channel as a source of randomness to simultaneously address various challenges in physical-layer security (PLS), quantum key distribution (QKD), and post-quantum cryptography (PQC). However, the long coherence time of atmospheric turbulence channels limits the achievable secret-key rates (SKRs). To address this issue, we initially leveraged the turbulence effects only during the system’s initialization phase. In this paper, we present a source-based secret key generation scheme that overcomes the limitations imposed by the long coherence time of the turbulent channel, without requiring initialization. The scheme utilizes both atmospheric turbulence and background radiation as sources of randomness. It offers security superior to PQC and is comparable to QKD, while enabling significantly higher SKRs, making it fully compatible with state-of-the-art optical communications.

IEEE AccessJan 1, 20254 citations

High Secret-Key Rate Atmospheric Turbulence-Based Cryptosystems

Ivan B. Djordjević

To overcome various problems of QKD, postquantum cryptography (PQC), and physical-layer security (PLS) encryption protocols, in our recent paper we have proposed to employ the atmospheric turbulent channel as the source of randomness in a source type PLS cryptosystem. However, a long coherence time of atmospheric turbulence channels limits the secret-key rates (SKRs). In this invited paper, we describe an encryption scheme that overcomes the problem of the long coherence time of the turbulent channel. The proposed scheme has security better than PQC and is comparable to QKD but enables significantly higher SKRs.

International Conference on Transparent Optical NetworksJul 6, 20250 citations

High secret-key rate atmospheric turbulence-based cryptosystems for asymmetric and non-line-of-sight communications

Ivan B. Djordjević

In our recent paper, we proposed the secret-key generation (SKG) scheme leveraging both atmospheric turbulence and background radiation as sources of randomness, which provides high secret-key rates and is compatible with state-of-the-art optical communications. Unfortunately, its application is limited to the symmetric line-of-sight free-space optical (FSO) links. In this paper, we propose two SKG schemes suitable for asymmetric and non-line-of-sight (NLOS) communications over FSO links. The proposed schemes employ turbulence, solar background radiation, and post-quantum cryptography-based randomly generated Alice and Bob's PSK sequences. To reduce the system cost, an unmodulated carrier is transmitted alongside the modulated PSK signal. On the receiver side, the coherent detection is performed by beating the unmodulated carrier with the received modulated signal on the PIN-photodetector (or the avalanche photodiode), followed by the DC blocker to remove undesired DC components. The proposed SKG schemes are applicable to both physical-layer security (PLS) cryptosystems and protocols similar to the quantum key distribution (QKD). The proposed SKG schemes show excellent tolerance to the atmospheric turbulence effects compared to the traditional PLS schemes. Experimental results indicate that the secret-key capacity of the NLOS SKG scheme is significantly higher than the corresponding traditional PLS counterpart.

Optics ExpressJun 17, 20260 citations

Secret key agreement for free-space optical communications over strong turbulence channels

Ning Wang, Xuegui Song, Julian Cheng +1 more

Security issues of terrestrial free-space optical (FSO) communications over strong atmospheric turbulence are investigated. Based on a subcarrier intensity modulated FSO system model, we first study the scintillation reciprocity of the system from a coherence time perspective. A private secret key-based cryptosystem with key management is introduced to enhance FSO security, and a key agreement approach is proposed based on statistics of the random atmospheric turbulence-induced fading channel measurements. Secret key rate of the key agreement scheme is studied for the strong turbulence channel characterized by the K-distribution. Practical key agreement protocol is designed based on channel identification.

GlobecomDec 1, 20142 citations

Free-space Continuous-Variable Quantum Key Distribution in moderate and strong atmospheric turbulence

Hailong Zhang, Xingran Chen, Jianhong Shi

Abstract Quantum Key Distribution (QKD) has been widely applied due to its theoretical one-time pad encryption. Typically employing laser beam as carrier, quantum states are transmitted through optical fibers or free-space channels, with the latter being more commonly adopted. However, compared to optical fibers, free-space links are more susceptible to external environmental factors, particularly atmospheric conditions. Beam propagation through the atmosphere experiences diffraction, refraction, and intensity attenuation, which can degrade key distribution efficiency and even prevent key generation at the receiver. The atmospheric turbulence poses the most significant challenge in all influencing factors, especially for the commonly encountered moderate-to-strong turbulence regimes. Therefore, in this work, we develop a phase screen model and turbulence-dominated transmittance model to comprehensively investigate the impact of various key parameters on optical beam propagation through turbulent atmospheres. Furthermore, we derive the key rate for the CV-QKD protocol using a TMSV (two-mode squeezed vacuum) state and perform numerical simulations.

Chinese Physics BMay 11, 20260 citations

Enhanced secret-key generation from atmospheric optical channels with the use of random modulation

Chun‐Yi Chen, Qiong Li

Secret-key extraction from atmospheric optical channels can generate common keys used by two communicating parties to encrypt their transmitted confidential information. The correlation time of turbulence-induced optical fluctuations imposes a restriction on the number of extracted uncorrelated key bits per second. To break this restriction, we propose a novel randomness sharing scheme between two communicating parties using an atmospheric optical channel equipped with random modulation and develop mathematical models for the common randomness source created by such a randomness-sharing scheme. Our randomness-sharing scheme provides the legitimate parties with the ability to decrease the temporal autocorrelation of the said common randomness source, which is called controllable common randomness source with memory (CCRSM), thereby enabling an enhanced secret-key extraction that can break the aforementioned restriction. Both the autocorrelation of the legitimate parties' observations of the CCRSM and the cross-correlation of the two legitimate parties' observations of the CCRSM are formulated and examined theoretically. It is found that the performing random modulation can decorrelate consecutive observations of the CCRSM obtained by the legitimate parties using a sampling interval smaller than the correlation time of turbulence-induced optical fluctuations. The cross-correlation coefficient of the eavesdropper's and legitimate parties' observations of the CCRSM is dealt with theoretically and the eavesdropping risk in the CCRSM-based key extraction is inspected for the fully-disclosed-single-modulation worst eavesdropping (FDSM-WE) scenario, partially-disclosed-single-modulation worst eavesdropping (PDSM-WE) scenario and double-modulation worst eavesdropping (DM-WE) scenario. It is shown that the FDSM-WE scenario has the highest degree of eavesdropping risk. Finally, the lowest limit of the secret-key capacity in consideration of using the CCRSM is theoretically formulated. The effects of random modulation on such the lowest limit are quantitatively analyzed from an information-theoretic perspective. It is manifested that random modulation does not harm the potential of extracting secret keys from the CCRSM's randomness component stemming from turbulence-induced optical fluctuations.

Optics ExpressOct 25, 202213 citations