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IEEE photonics journal

Integrated Physical Layer Key Distribution by Optical Steganography in Quantum Noise Stream Cipher System

Yuanxiang Wang, Hanwen Luo, Tian Qiu, Linsheng Zhong, Xiaoxiao Dai, Qi Yang, Lei Deng, Deming Liu, Mengfan Cheng

Published Nov 11, 2024• 1 citation
Publisher

Abstract

To counter heterodyne measurements, correlation attacks, and known plaintext attacks, seed key refresh is critical to the security of a quantum noise stream cipher system. Integrated key distribution is an important means to reduce the deployment cost, as key exchange and public transmission are performed over the same channel. In this paper, we propose a novel method for integrated key distribution by optical steganography based on dither-remodulation in a bias controller of the Mach-Zehnder modulator. No extra wavelength or bandwidth is used for the stealth channel, which is transmitted together within the public channel. The concealing depth of the stealth signal reaches −36.2 dB, and its steganographic effect provides additional security, which further improves the overall security of the optical physical layer. The bidirectional stealth transmission can support light-weight temporary key exchange mechanism, combined with asymmetric encryption algorithm, to achieve high security and forward/backward security of seed keys. We experimentally demonstrate a real-time integrated key distribution via optical steganography in a QNSC system. The experimental results show that a real-time bidirectional stealth link is established at a rate of 1 kbps in a fiber transmission distance of 97 km for a public QNSC transmission at a rate of 32 Gbps, providing a seed key refresh frequency of over 1 Hz.

DOI
10.1109/jphot.2024.3495834

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To counter heterodyne measurements, correlation attacks, and known plaintext attacks, seed key refresh is critical to the security of a quantum noise stream cipher system. Integrated key distribution is an important means to reduce the deployment cost, as key exchange and public transmission are performed over the same channel. In this paper, we propose a novel method for integrated key distribution by optical steganography based on dither-remodulation in a bias controller of the Mach-Zehnder modulator. No extra wavelength or bandwidth is used for the stealth channel, which is transmitted together within the public channel. The concealing depth of the stealth signal reaches −36.2 dB, and its steganographic effect provides additional security, which further improves the overall security of the optical physical layer. The bidirectional stealth transmission can support light-weight temporary key exchange mechanism, combined with asymmetric encryption algorithm, to achieve high security and forward/backward security of seed keys. We experimentally demonstrate a real-time integrated key distribution via optical steganography in a QNSC system. The experimental results show that a real-time bidirectional stealth link is established at a rate of 1 kbps in a fiber transmission distance of 97 km for a public QNSC transmission at a rate of 32 Gbps, providing a seed key refresh frequency of over 1 Hz.
The physical layer transmission security is a promising technology against security threats. As an effective supplement to the encryption strategy, steganography has received widespread attention. We report a real-time 2 kbps stealth transmission in the 10 Gbps dual polarization QPSK public optical communication. The stealth data is embedded in dither signals via precise and stable bias control technique for a Mach-Zehnder modulator. In the receiver, the stealth data can be recovered from the normal transmission signals by low SNR signal processing and digital down conversion. The stealth transmission has been verified to pose almost no impact on the public channel over a 117 km distance. The proposed scheme is compatible with existing optical transmission systems, so that no new hardware needs to be employed. It can be accomplished and is exceeded economically by adding simple algorithms, which utilizes only a small amount of FPGA resources. The proposed method can cooperate with encryption strategies or cryptographic protocols at different network layers to reduce the communication overhead and improve the overall security of the system.
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.
We propose and experimentally demonstrate a compatible physical-layer secure optical communication (PLSOC) system that integrates self-adaptive physical-layer key distribution (PLKD) and encryption (PLE) in optical coherent communication. Based on bit error rate difference of QAM signals mapped by asymmetric basis state Y-00 protocol, the secret key can be secretly exchanged over public fiber links without the pre-shared keys. Moreover, we perform a parameter self-adaptive strategy for practical and dynamic PLKD. The security of the key is evaluated in the case of a fiber-tapping attack. A secure hash algorithm, SHA3-512, is used to perform privacy amplification to obtain the virtually secure key. An error-free PLKD rate reaches 39.3 Kbits/s over 300 km ultra-low loss fiber. We experimentally enable the integration of the proposed PLKD scheme and quantum noise stream cipher (QNSC) with a single wavelength, same system. Q factor penalty of the integration system compared to the QNSC system is 3.7 dB (optical back-to-back) and 4.8 dB (300 km) respectively. By exploiting a common hardware platform, with the same wavelength, the proposed PLSOC system addresses the problem that PLKD and PLE are separately performed through independent optical fiber links or wavelengths. Since only digital signal processing is used, the scheme does not require extra hardware.
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.
In this paper, we propose a novel physical layer security optical transmission scheme utilizing randomized quantization noise. The proposed approach encrypts low-order plaintext signals into ultra-high-order ciphertext using principles similar to quantum noise stream cipher (QNSC). While, the ultra-dense quadrature amplitude modulation (QAM) ciphertext waveforms are masked by intrinsic quantization noise. The combination of digital delta-sigma quantization and analog chaotic random scrambling not only produces randomized quantization noise, but also naturally supports one-time processing of masking ciphertext and generating keystream. Whereby, the in-band quantization noise (IBN) conceals nearby ciphertext levels bolstering security, and the out-of-band quantization noise (OOBN) is digitized to generate keystream using the Toeplitz hashing extractor. Experimental results show that 256-QAM plaintext signals were securely transmitted over standard single-mode fiber: 163-Gbps signals over 400 km, and 79.7-Gbps signals over 1800 km. To evaluate system performance, theoretical models for signal-to-noise ratio (SNR), bit error rate (BER), and number of masked signals (NMS) are derived as functions of the oversampling ratio (OSR). Our findings reveal a trade-off between transmission performance and security performance. Our results confirm that this scrambling effectively eliminates the correlation between the masking noise components. Toeplitz hashing extractor can effectively reduce the complexity of keystream generation and obtain a source-independent random keystream.
We propose and experimentally demonstrate a secure quantum noise stream cipher transmission system that integrates key generation and distribution. At the stage of carrier phase recovery, the estimated phase noise is used to generate randomness keys without additional equipment. Based on direct sequence spread spectrum technology, we integrate the distributed keys with quantum noise stream cipher signals. The key distribution and encryption transmission can be completed simultaneously without occupying additional bandwidth or time slots. By changing the position of distributed keys in the encryption base, the BER performance of QAM/QNSC signals cannot be affected by the keys. Experimental results demonstrate that the 54.5 Mbps key distribution and 31 Gbps encryption transmission without OSNR penalty can be achieved simultaneously over a 120 km standard single-mode fiber.