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IEEE Communications Letters

Physical Layer Secure Key Distribution Based on Artificial Amplitude Noise in QAM/QNSC Optical Communication Systems

Shuang Wei, Yajie Li, Kongni Zhu, Chao Lei, Yuang Li, Mengwen Pan, Wei Min Wang, Yongli Zhao, Jie Zhang

Published Jul 17, 2023• 14 citations
Publisher

Abstract

In the quantum noise stream cipher (QNSC) system, the low-order plaintext is encrypted by pre-shared keys into high-order ciphertext. However, high-speed optical communication systems have a huge demand for pre-shared keys. On the other hand, the separation of the secure communications sub-system from the secure key distribution (SKD) sub-system increases potential security risks and introduces additional resources overhead. In this letter, we propose an artificial amplitude noise-based SKD scheme (AAN-SKD) in QAM/QNSC to generate secret key for legal parties accordingly. The two orthogonal PAM symbols are superimposed to generate QAM symbols. Thus, the AAN-SKD can also be implemented in PAM modulation. In addition, the data transmission and AAN-SKD are completed in the same channel. Experimental results indicate that the key generation rate and key consistency ratio of the proposed scheme can reach$188.22Mbit/s$and 91%, respectively. Compared with quantum key distribution, the AAN-SKD has the advantage of lower cost, better compatibility, and a higher key rate.

DOI
10.1109/lcomm.2023.3295809

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Quantum noise stream cipher (QNSC) is a physical-layer encryption approach for optical communications, and its security barrier is the "basis" that is used as the secret-key for symbol encryption. Regarding the fact that the basis is actually transmitted through the fiber, we propose a basis precoding scheme based on probabilistic constellation shaping, to better conceal the basis into the noise for security enhancement. Experimental results show our scheme can improve the security of the QAM/QNSC system in terms of Eve’s symbol error ratio.

International Conference on Optical Network Design and Modeling (ONDM)•May 8, 2023•3 citations
In the quantum noise stream cipher (QNSC) system, the low-order plaintext is encrypted by pre-shared keys into high-order ciphertext. However, high-speed optical communication systems have a huge demand for pre-shared keys. On the other hand, the separation of the secure communications sub-system from the secure key distribution (SKD) sub-system increases potential security risks and introduces additional resources overhead. In this letter, we propose an artificial amplitude noise-based SKD scheme (AAN-SKD) in QAM/QNSC to generate secret key for legal parties accordingly. The two orthogonal PAM symbols are superimposed to generate QAM symbols. Thus, the AAN-SKD can also be implemented in PAM modulation. In addition, the data transmission and AAN-SKD are completed in the same channel. Experimental results indicate that the key generation rate and key consistency ratio of the proposed scheme can reach188.22Mbit/s188.22Mbit/s188.22Mbit/sand 91%, respectively. Compared with quantum key distribution, the AAN-SKD has the advantage of lower cost, better compatibility, and a higher key rate.
An ultra-high-order QAM quantum noise stream cipher (QNSC) scheme assisted by intensity and phase chaotic encryption is proposed. In this scheme, the legal transmitter (Alice) first encrypts the original low-order QAM signal into an ultra-high-order QAM signal according to the pre-shared seed key based on the Y-00 protocol, and then conceals the intensity and phase information of the ultra-high-order QAM signal through the intensity and phase chaos generated from a nonlinear delay chaotic source for enhancing the security. The intensity and phase chaotic carrier can be eliminated by the open-loop chaotic synchronization module at the legal receiver (Bob). The scheme was numerically verified in 112 Gbit/s (28 GBaud 16QAM plaintext) and 168 Gbit/s (28 GBaud 64QAM plaintext) 65536QAM/QNSC systems, which can achieve 600 km and 150 km transmission at 7% HD-FEC threshold, and 1000 km and 350 km transmission at 20% SD-FEC threshold, respectively. Meanwhile, the number of masked signals (NMS) and the detection failure probability (DFP) in the scheme are obviously higher than in the original QAM/QNSC system. We believe that the proposed scheme is a promising strategy for enhancing the security of QAM/QNSC transmission systems.
Among physical layer encryption schemes, the quantum noise stream cipher (QNSC) has garnered significant attention due to its compatibility with high-speed commercial fiber-optic communication systems. After careful analysis of the encryption scheme, we reveal that QNSC transmission systems exhibit a security vulnerability in their encoding scheme. This vulnerability limits quantum noise to alerting high-order information bits in plaintext-dependent regions, creating structured ciphertext concealment. Numerical simulation and experimental verification both indicate that an eavesdropper can use quantization-attack to crack this vulnerability. Existing security assessment methods will overestimate the system’s security under quantization-attack. In addition, system security demonstrates a strong linear dependence on the plaintext modulation format, rather than the ciphertext modulation format as is widely presumed. To further enhance system security, the probability distribution is further introduced into the encoding process of ciphertext. The experiment results show that we not only achieved random concealment of ciphertext by quantum noise but also enhanced the eavesdropper’s symbol error rate by ∼86 % and maximally expanded the key space of the QAM-QNSC system by 2 27.2 .
We have been intensively studying quantum noise stream cipher (QNSC) transmission technique using quadrature amplitude modulation (QAM) with a view to realizing a high-speed and long-distance secure communication system [1]. In this talk, we describe our recent demonstration of an on-line 70 Gbit/s, 128 QAM/QNSC transmission over 100 km with a continuous variable quantum key distribution (CV-QKD) system [2], in which a shared key is transmitted online via the CV-QKD so that the key is shared for a certain time period with absolutely no risk of being eavesdropped.
Quantum Noise Stream Cipher (QNSC) has emerged as a physical-layer encryption technique that exploits quantum noise and non-orthogonal coherent-state modulation to secure optical communication. However, the security of QNSC relies exceedingly on the secrecy and freshness of its seed key. Quantum Key Distribution (QKD), on the other hand, provides information-theoretically secure key exchange rooted in the laws of quantum mechanics. The convergence of these two paradigms, i.e., integrated QKD-QNSC architectures, offers a compelling solution to each of their limitations. In such integrated systems, QKD continuously supplies and refreshes the secret seed key that governs QNSC modulation. Thus, governing a unified security framework that couples provably secure key establishment with high-speed quantum-enhanced physical-layer encryption. This work presents a comprehensive review of QNSC systems, examining their operating principles, security models under various attacks, and their integration with QKD systems. We analyze the security interplay between the key generation and encryption layers and survey experimental demonstrations and architectural progress toward practical deployment. Furthermore, we identify the open challenges and future research directions that must be addressed to realize fully integrated, quantum-secured optical communication networks at a practical scale.
【Objective】To further enhance the security of the Intensity Modulated (IM) / Quantum Noise Stream Cipher (QNSC) system, this paper proposes a security enhancement scheme for the IM/QNSC system assisted by chaotic encryption.【Methods】In this scheme, the legitimate transmitter encrypts the low-order 4-level Pulse Amplitude Modulation (PAM-4) signal into an ultra-high-order PAM-256 signal. Then it uses the intensity chaos generated by a nonlinear delayed chaos source to encrypt the ultra-high-order PAM signal, so as to enhance the security of the IM/QNSC system.【Results】This scheme was numerically verified in IM/QNSC dispersion-managed transmission systems with rates of 56 and 112 Gbit/s. The results show that under the 7% Hard Decision-Forward Error Correction (HD-FEC) threshold, the 56 and 112 Gbit/s encrypted systems achieve transmissions of 400 and 300 km. Under the 20% Soft Decision-Forward Error Correction (SD-FEC) threshold, they achieve transmissions of 700 and 600 km. The security analysis of the scheme shows that the Number of Masked Symbols (NMS) and Detection Failure Probability (DFP) of the scheme are higher than those of the original IM/QNSC system.【Conclusion】Chaotic encryption assistance amplifies the eavesdropping noise in the QNSC system. Compared with the original IM/QNSC system, it improves the system security.
Quantum noise stream cipher (QNSC) is a physical-layer encryption approach for optical communications, and its security barrier is the "basis" that is used as the secret-key for symbol encryption. Regarding the fact that the basis is actually transmitted through the fiber, we propose a basis precoding scheme based on probabilistic constellation shaping, to better conceal the basis into the noise for security enhancement. Experimental results show our scheme can improve the security of the QAM/QNSC system in terms of Eve’s symbol error ratio.