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Photonics

Key Space Enhanced Correlated Random Bit Generation Based on Synchronized Electro-Optic Self-Feedback Loops with Mach–Zehnder Modulators

Chuyun Huang, Xulin Gao, Sile Wu, Wenfu Gu, Biao Su, Yuncai Wang, Yuwen Qin, Zhensen Gao

Published Dec 9, 2022• 5 citations
Publisher

Abstract

With the widespread application of big data, the amount of data transmitted through optical networks has been increasing dramatically. Correlated random bit generation (CRBG) is one of the key technologies in secure communication systems to ensure security performance and transmission efficiency. We propose and demonstrate a CRBG scheme based on a Mach–Zehnder modulator (MZM) electro-optic feedback loop to improve the security and speed of communication systems. In this scheme, common-signal-induced synchronization is accomplished to generate wideband complex physical entropy sources, and a private hardware module is employed to perform post-processing and nonlinear transformation of the synchronized signal. The simulation results show that the effective bandwidth of the output chaotic signal is significantly increased to 27.76 GHz, and high-quality synchronization with a correlation coefficient of over 0.98 is reached. A high-rate CRBG of up to 5.3 Gb/s is successfully achieved between two synchronized wideband physical entropy sources, and the hardware key space is enhanced to ∼242, which greatly improves the privacy of physical entropy sources. The proposed scheme provides a promising approach for high-speed private CRBG, which is expected to be used in high-speed secure key distribution and optical communication systems.

DOI
10.3390/photonics9120952

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With the widespread application of big data, the amount of data transmitted through optical networks has been increasing dramatically. Correlated random bit generation (CRBG) is one of the key technologies in secure communication systems to ensure security performance and transmission efficiency. We propose and demonstrate a CRBG scheme based on a Mach–Zehnder modulator (MZM) electro-optic feedback loop to improve the security and speed of communication systems. In this scheme, common-signal-induced synchronization is accomplished to generate wideband complex physical entropy sources, and a private hardware module is employed to perform post-processing and nonlinear transformation of the synchronized signal. The simulation results show that the effective bandwidth of the output chaotic signal is significantly increased to 27.76 GHz, and high-quality synchronization with a correlation coefficient of over 0.98 is reached. A high-rate CRBG of up to 5.3 Gb/s is successfully achieved between two synchronized wideband physical entropy sources, and the hardware key space is enhanced to ∼242, which greatly improves the privacy of physical entropy sources. The proposed scheme provides a promising approach for high-speed private CRBG, which is expected to be used in high-speed secure key distribution and optical communication systems.
We propose and experimentally demonstrate a novel, to the best of our knowledge, private correlated random bit generation (CRBG) scheme based on commonly driven induced synchronization of two wideband physical entropy sources, which employs an open-loop distributed feedback laser followed by a hybrid electro-optic nonlinear transformation hardware module for effective bandwidth expansion and privacy enhancement. A Mach-Zehnder interferometer followed by an electro-optic self-feedback phase modulation loop as well as a dispersion element are constructed as a private hardware module to perform post-processing and nonlinear transformation of the synchronized signal. A record high rate of 5.2-Gb/s CRBG is successfully achieved between two synchronized wideband physical entropy sources with an enhanced entropy source rate and hardware key space. The demonstrated scheme may provide a new way for CRBG in future high speed secure communication systems.
Correlated random bit generation (CRBG) plays an important role in secure communication, particularly for secure key distribution. In this work, we propose and numerically demonstrate a scheme of CRBG based on multi-channel broadband entropy sources and parallel filtering. In this scheme, a chaotic optical frequency comb generator is employed to produce a chaotic frequency comb with multi-channel low-correlated wideband chaos. Based on the commonly driven induced synchronization between two closed-loop distributed feedback lasers and chaotic frequency comb generation, synchronized multi-channel wideband chaos is achieved. Then, parallel filtering is implemented by utilizing an arrayed-waveguide grating to divide the chaotic frequency comb into multi-channel sub-carrier chaos with different wavelengths. To reduce the correlation among adjacent channels and improve the chaos complexity, beating frequency processing with different delay times among adjacent chaotic sub-carriers is performed to get several different sets of chaotic output, among which an enhanced bandwidth over 20 GHz and low correlations are obtained. Moreover, the correlation between the chaotic output and the driving signal can be further suppressed, indicating that the security of the scheme is guaranteed. Multi-channel high-speed CRBG with a total generation rate of 16 Gb/s is successfully achieved at two legitimate users after transmission, with the randomness of multi-channel correlated bit generation verified using a test suite from the National Institute of Standards and Technology. The proposed scheme may provide a way for high-speed multi-channel parallel correlated random bits based on commercial components, which could potentially find applications in future secure optical communication systems.
We propose and experimentally demonstrate a novel, to the best of our knowledge, correlated random bit generation (CRBG) scheme in virtue of the synchronization of two physical entropy sources that are composed of a continuous-wave laser, a phase modulator that is driven by the output of a local laser subject to constant-amplitude and random-phase (CARP) injection, as well as a dispersive component. It is experimentally indicated that wideband complex physical entropy sources with an effective bandwidth of 22 GHz can be achieved, and high-quality synchronization with a large cross-correlation coefficient (∼0.95) can be achieved by introducing symmetric CARP injections into the local lasers at Alice and Bob ends. Based on this, two distributed CRBSs with a bit rate over 3 Gb/s and satisfactory consistency are independently generated at Alice and Bob ends; the excellent randomness of CRBSs is verified using a test suite of the National Institute of Standards and Technology.
We experimentally demonstrate a chaotic synchronization scheme based on the electro-optic hybrid entropy sources. The chaos synchronization method is experimentally validated that 200 km high-level chaos synchronization can be attained and the distance can be further extended. The digital signal induced chaos synchronization signal has good robustness against the potential distortions in long-haul optical transmission. On the basis of the digital signal induced chaos synchronization strategy, a correlated random bit generation (CRBG) scheme with bit rate of 1.25 Gb/s and distance of 200 km is proposed. The generated correlated random bit sequences (CRBSs) pass all the NIST tests. Meanwhile, a data encryption scheme based on the robust chaos synchronization method is proposed with low computation complexity. The synchronization signal, in which the encrypted data is embedded, maintains the strength in long-haul transmission. The strong robustness of the scheme under parameter mismatch is numerically analyzed. These propositions show great potential in the field of secure communication, especially the long-haul scenario.
High speed physical secure key distribution in a classical optical fiber channel is unprecedentedly desired for modern secure communication, but it still remains a worldwide technical challenge. In this paper, we propose and experimentally demonstrate a novel high-speed physical secure key distribution scheme based on chaotic optical signal processing and private hardware modules, which employs chaotic self-carrier phase modulation for chaotic bandwidth expansion and time-delayed shift keying of commonly driven synchronized optical chaos for physical layer security. In this scheme, the entropy source rate of synchronized chaos output from two remote response lasers is greatly expanded by chaotic self-carrier delayed nonlinear phase disturbance, which facilitates high speed key extraction from the entropy source with guaranteed randomness. Moreover, a synchronization recovery time of sub-nanosecond is achieved by dynamic keying of the chaotic delay time after chaos synchronization to accelerate the key distribution rate. Based on the proposed scheme, a high physical key distribution rate of 2.1 Gb/s over 40 km is successfully demonstrated in the experiment. The proposed solution provides a promising strategy for future high-speed key distribution based on chaotic optical signal processing and classical fiber channel.
We propose and experimentally demonstrate a novel physical layer encryption scheme for high-speed optical communication. A 10 Gb/s on-off keying signal is secretly transmitted over 100 km standard single-mode fiber. The intensity-modulated message is secured by the encryption mechanism, which is composed of an external noise source and an internal time-delayed feedback loop. The external noise serves as an entropy source with sufficient randomness. The feedback loop structure in the transmitter introduces a time-domain encryption key space, and a corresponding open-loop configuration at the receiver side is used for synchronization and decryption. Experiment results show the effectiveness of the proposed scheme. For a legitimate terminal, bit error rate below 10−8 can be obtained. Decryption degradations with the mismatch of different hardware parameters are researched. The time delay in the feedback loop provides a sensitive encryption key. For other hardware parameters, the system is robust enough for synchronization. Meanwhile, the time-delay signature of the loop is able to be well concealed by the external noise. Moreover, the proposed scheme can support density wavelength division multiplexing transmission with a relatively simple structure. This work also provides a new concept to establish optical secure communication by combining a time-delayed feedback chaotic system and random noise.