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International Conference on Optical Communications and Networks (ICOCN)

I/Q-Combined Encryption and Decryption in Single Carrier QAM Quantum Noise Stream Cipher

Yuang Li, Yajie Li, Chao Lei, Kongni Zhu, Yongli Zhao, Jie Zhang

Published Aug 12, 2022• 1 citation
Publisher

Abstract

We propose a QAM/QNSC scheme based on I/Q- combined encryption and decryption, which directly recovers low-order signal phase noise after decryption. Simulation results show that the maximum tolerable laser beat linewidth is$\sim 4\times 10^{-4}$. The proposed scheme simplifies the implementation of DSP and avoids the dependence on ultra-narrow-linewidth lasers.

DOI
10.1109/icocn55511.2022.9901034

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We propose a QAM/QNSC scheme based on I/Q- combined encryption and decryption, which directly recovers low-order signal phase noise after decryption. Simulation results show that the maximum tolerable laser beat linewidth is∼4×10−4\sim 4\times 10^{-4}∼4×10−4. The proposed scheme simplifies the implementation of DSP and avoids the dependence on ultra-narrow-linewidth lasers.
Quantum noise stream cipher based on quadrature-amplitude-modulation (QAM/QNSC) is a kind of physical layer encryption technology. However, the additional encryption penalty will significantly affect the practical deployment of QNSC, especially in the high capacity and long-haul transmission system. With our research, the encryption process of QAM/QNSC degrades the transmission performance of plaintext information. In this paper, we quantitatively analyze the encryption penalty of QAM/QNSC based on the proposed concept of effective minimum Euclidean distance. We calculate the theoretical signal-to-noise ratio sensitivity and encryption penalty of QAM/QNSC signals. A modified feedforward pilot-aided two-stage carrier phase recovery scheme is used to reduce the effect of laser phase noise and the encryption penalty. Experimental results achieve single-channel 205.9 Gbit/s 640km transmission with single carrier polarization-diversity-multiplexing 16-QAM/QNSC signal.
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.
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.
With the use of a 40 Gbit/s quantum noise stream cipher (QNSC) transmitter and receiver, we succeed in the first secure optical transmission exceeding 1 Tbit/s/λ over 560 km by combining 29 optical carriers generated from a single light source. In addition to amplitude and phase encryption, time-domain masking is newly introduced to further enhance the security of the random sequence used for encryption. This three-dimensional QNSC scheme employs irregular mapping of the QAM constellation, together with symbol order shuffling in the time domain. As a result of the time-domain shuffling, the BER at an eavesdropper reaches 0.5 for each bit within a symbol, even when the irregular mapping is decrypted.
With the use of a 40 Gbit/s quantum noise stream cipher (QNSC) transmitter and receiver, we succeed in the first secure optical transmission exceeding 1 Tbit/s/λ over 560 km by combining 29 optical carriers generated from a single light source. In addition to amplitude and phase encryption, time-domain masking is newly introduced to further enhance the security of the random sequence used for encryption. This three-dimensional QNSC scheme employs irregular mapping of the QAM constellation, together with symbol order shuffling in the time domain. As a result of the time-domain shuffling, the BER at an eavesdropper reaches 0.5 for each bit within a symbol, even when the irregular mapping is decrypted.
A quantum noise stream cipher scheme (QNSC) based on triangular quadrature amplitude modulation (TQAM) and the secret probabilistic shaping (SPS) is studied. Compared with rectangular quadrature amplitude modulation (QAM), TQAM is a more compact symmetrical structure, which results in better transmission performance and greater noise masking number. Then, SPS is realized, where the probabilistic shaping information as the secret key is masked into noise and transmitted with the encrypted signal simultaneously. The combination of SPS and QNSC makes it impossible for an attacker to obtain the ciphertext, which enhances the security of QNSC scheme without introducing additional key. TQAM and probabilistic shaping improve the transmission performance of QNSC scheme. Under 7% forward error correction (FEC) threshold in back-to-back system, compared with QAM/QNSC systems, TQAM/QNSC provides an OSNR gain of ∼ 0.6 dB, and SPS-TQAM/QNSC provides an OSNR gain of ∼ 1.2 dB. The proposed scheme is demonstrated with the net data rate of 34.28 Gbit/s over 140 km single-span standard single mode fiber.