Secure optical transmission in single-user channel using encrypted wireless CDMA codes

Peter A. Schulz, Thomas H. Shake

Yeteng Tan, Tao Pu, Jilin Zheng +3 more

Optical CDMA transmission systems can not only increase system capacity, but also achieve physical-layer security against fiber tapping attacks. In this paper, we examine the information-theoretic security of optical CDMA systems by evaluating the trade off between the achieved information capacity and the confidentiality. In particular, we established a wiretap channel model of optical CDMA systems, based on which we have evaluated the impacts of key system parameters, such as the type of code words, the number of users M , the code lengths N and the input optical power P , on the system security. Our results indicate that key system parameters play an important role and choosing suitable values of these system parameters will be helpful to improve the secure performance of optical CDMA systems to some degree. For example, choosing the code words whose cross-correlation λ values are smaller, increasing the code lengths N or the input optical power P and reducing the number of users M properly can all be used to improve the secure performance of optical CDMA systems.

Yixue Du, Fei Xue, S. J. Ben Yoo +1 more

This paper presents a simple and effective security enhancement mechanism for spectral phase-encoded time spread (SPECTS) optical code-division multiple-access (O-CDMA) users against eavesdroppers tapping at the isolated single-user uplink stream. Traditional SPECTS O-CDMA users apply pseudorandom spectral phase codes to spread ON-OFF keyed ultrashort optical pulses in time. Isolated single-user upstream transmission is prone to energy detection by eavesdroppers, even those without code knowledge. In addition, it has been shown that the use of a pair of (bright/dark) codes to represent binary data transmission is still susceptible to differential phase shift keying (DPSK) eavesdroppers without code knowledge. To remedy this security weakness, we introduce a new type of O-CDMA data modulation with memory. This new method not only effectively defeats DPSK eavesdropping but also can provide good detection performance for authorized users. We successfully demonstrate the concealment of information from DPSK eavesdroppers with different levels of modulation information.

Jawad A. Salehi

Shusaku Hata, Hiroyuki Yashima

Yuchao Liu, Tao Wang, Lang Li +6 more

The quantum noise stream cipher (QNSC) scheme, grounded in Heisenberg’s uncertainty principle, can facilitate secure communication by employing noise to obfuscate multi-base encrypted signals. The current research primarily focuses on point-to-point performance, while studies on point-to-multipoint schemes remain limited due to compatibility issues with multiple access technologies. This study presents a QNSC scheme for passive optical networks based on code-division multiple access (CDMA). In our scheme, different user datasets are combined into one dataset via CDMA and then encrypted using the QNSC protocol. Each user can recover their corresponding dataset from the encrypted signal by employing the same security keys along with a distinct pseudo-noise code (PN code). Through simulation studies, we found that under the condition of being able to decode correctly, as the number of users increases, the optical signal-to-noise ratio (OSNR) at the receiver decreases, which leads to a gradual rise in the eavesdropper’s detection failure probability (DFP). Furthermore, the network capacity is correlated with the number of modulation bits, as the increase in modulation bits directly translates to an enhancement in the data’s carrying capability. We have conducted verification experiments, and the results confirmed that four users can acquire 64 QAM/QNSC plaintext data with an average transmission rate of 600 Mbit/s over a transmission distance of 20 km. These data were encrypted in the constellation with 64×64 symbols, achieving a DFP of up to 99.3%, and each user successfully decoded them via CDMA. We have successfully extended the fundamental point-to-point QNSC scheme to accommodate point-to-multipoint passive optical networks, establishing the foundational framework for the future large-scale deployment of quantum networks.