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arXiv:1709.06755

Experimental unconditionally secure covert communication in dense wavelength-division multiplexing networks

Yang Liu, Juan Miguel Arrazola, Wen‐Zhao Liu, Weijun Zhang, Ignatius William Primaatmaja, Hao Li, Lixing You, Zhen Wang, Valerio Scarani, Qiang Zhang, Jian-Wei Pan

Published Sep 20, 2017• 4 citations
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Abstract

Covert communication offers a method to transmit messages in such a way that it is not possible to detect that the communication is happening at all. In this work, we report an experimental demonstration of covert communication that is provably secure against unbounded quantum adversaries. The covert communication is carried out over 10 km of optical fiber, addressing the challenges associated with transmission over metropolitan distances. We deploy the protocol in a dense wavelength-division multiplexing infrastructure, where our system has to coexist with a co-propagating C-band classical channel. The noise from the classical channel allows us to perform covert communication in a neighbouring channel. We perform an optimization of all protocol parameters and report the transmission of three different messages with varying levels of security. Our results showcase the feasibility of secure covert communication in a practical setting, with several possible future improvements from both theory and experiment.

DOI
10.48550/arxiv.1709.06755

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Covert communication offers a method to transmit messages in such a way that it is not possible to detect that the communication is happening at all. In this work, we report an experimental demonstration of covert communication that is provably secure against unbounded quantum adversaries. The covert communication is carried out over 10 km of optical fiber, addressing the challenges associated with transmission over metropolitan distances. We deploy the protocol in a dense wavelength-division multiplexing infrastructure, where our system has to coexist with a co-propagating C-band classical channel. The noise from the classical channel allows us to perform covert communication in a neighbouring channel. We perform an optimization of all protocol parameters and report the transmission of three different messages with varying levels of security. Our results showcase the feasibility of secure covert communication in a practical setting, with several possible future improvements from both theory and experiment.
Covert communication offers a method to transmit messages in such a way that the communication is undetected. Yet, unconditional secure covert communication has not yet been achieved. In this work, we report an experimental demonstration of covert communication that is provably secure against quantum adversaries. We deploy the protocol in a dense wavelength-division multiplexing infrastructure, where our system coexists with a co-propagating C-band classical channel over 10 km of optical fiber. The noise from the classical channel, generally a negative factor in quantum communication, allows us to perform covert quantum communication in a neighboring channel. We report the transmission of three different messages with varying levels of security. Our results demonstrate the feasibility of secure covert communication in a practical setting, which shall find immediate application in optical communication.
Photonic layer security is demonstrated over 200 km of a loaded dense wavelength-division multiplexing (DWDM) network. The secure channel achieves 100 Gbps throughput with photonic-encrypted coherent transmission and continuously updating photonic keys. The signal is effectively concealed under optical noise, harvest-proof, and lacks offline decryption capabilities, ensuring post-quantum resilience. Additionally, successful coexistence with seven conventional coherent channels, both in-band and out-of-band, is demonstrated in a real-world scenario.
This paper presents the practical development of a hybrid quantum-classical network through multiple links of four- and seven-core industrial jacketed multicore fiber. The network utilizes dense wavelength division multiplexing to propagate the C-band quantum and classical information in the same core, making full use of the unidirectional nature of quantum key distribution. Total network transmission of 1.16 Tbps is achieved with a total network secret key rate of approximately 7.4 kbps through a combination of 1 and 2 km links of multicore fiber. The deployment configurations presented are independent of the classical modulation format, and the maximal transmission rate for an operational hybrid network is found to be dependent only on classical optical power occupying the quantum channel wavelength. A model was developed to estimate the impact classical optical channels will have on coexisting quantum channels, which may allow engineers to quickly validate hybrid network designs.
Wavelength division multiplexing (WDM) of quantum key distribution (QKD) with classical optical channels has been proven to be feasible experimentally. In this paper, we will analyze the practical security of WDM-QKD theoretically. Specifically, we first establish the noise model of classical signals. Then, the influence of classical noises on the performance of decoy-state WDM-QKD is studied with a finite-key security analysis. For numerical simulations, the effect of classical noise-reduction methods for different experimental settings is given. The secret key rate and maximum transmission distance of WDM-QKD is simulated with various sent number of quantum pulses or transmitted power of classical signals. Furthermore, the performance of two kinds of decoy-state WDM-QKD is compared, which shows that the optimal decoy-state protocol for WDM-QKD is related to the sent number of quantum pulses. Since WDM-QKD is desired to reduce the cost of QKD networks and since experiments have already been carried out, our work can not only close the gap between theory and practice, but also be used to optimize the experimental parameters and improve its performance.
Optical communication networks are easy to be eavesdropped by attackers, and traditional encryption algorithms have become more and more difficult to ensure the security of information transmission. Different from the traditional encryption algorithm, optical covert communication processes the signal at the physical layer, and improves the security and reliability of the system by hiding the optical signal in the public channel. Based on a typical microwave photonic filter, an optical covert communication scheme is proposed. On the one hand, the microwave photonic filter makes the scheme imperceptible. On the other hand, the randomness of complementary coding makes the scheme confidential. The feasibility of the scheme is analyzed theoretically, and the experimental results show that the covert channel is successfully transmitted over 50 km single-mode fiber.
Computational encryption, information-theoretic secrecy and quantum cryptography offer progressively stronger security against unauthorized decoding of messages contained in communication transmissions. However, these approaches do not ensure stealth--that the mere presence of message-bearing transmissions be undetectable. We characterize the ultimate limit of how much data can be reliably and covertly communicated over the lossy thermal-noise bosonic channel (which models various practical communication channels). We show that whenever there is some channel noise that cannot in principle be controlled by an otherwise arbitrarily powerful adversary--for example, thermal noise from blackbody radiation--the number of reliably transmissible covert bits is at most proportional to the square root of the number of orthogonal modes (the time-bandwidth product) available in the transmission interval. We demonstrate this in a proof-of-principle experiment. Our result paves the way to realizing communications that are kept covert from an all-powerful quantum adversary.