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International Conference on Transparent Optical Networks

Securing the Speed: Harvest-Immune Photonic Layer Security in DCI and Metro Networks

Dan Sadot, Eyal Wohlgemuth, Ido Attia, Ohad Balasiano, Isaak Jonas, Elimelech Keller, Hamutal Shalom

Published Jul 14, 2024• 0 citations
Publisher

Abstract

The concept of “harvest now, decipher later” presents a major data security concern in light of thriving quantum computing, rendering traditional public-key cryptography ineffective and undermining even state-of-the-art symmetric block ciphers. Physical layer security (PLS) offers advantages such as enhancing the security of the entire OSI model, including its metadata, with minimal latency and providing robust protection against data harvesting. Multi-THz, high repetition rate mode-locked laser sources have enabled the development of PLS techniques that leverage coherent optical spreading and despreading, phase mask encoding, and under-the-noise transmission. Since capturing multi-THz E-fields is impractical, real-time all-optical decoding is necessary, as offline post-processing yields permanently poor performance (indicated by a negative SNR) for unauthorized detection. This paper reports the demonstrations of PLS transmission of 30 G and 60G Bauds, using QPSK and 16-QAM modulation schemes, achieved over distances of up to 100 km, with a real-time DSP ASIC. These achievements pave the way for high-bandwidth point-to-point harvest-immune optical connectivity.Introduction

DOI
10.1109/icton62926.2024.10648059

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The concept of “harvest now, decipher later” presents a major data security concern in light of thriving quantum computing, rendering traditional public-key cryptography ineffective and undermining even state-of-the-art symmetric block ciphers. Physical layer security (PLS) offers advantages such as enhancing the security of the entire OSI model, including its metadata, with minimal latency and providing robust protection against data harvesting. Multi-THz, high repetition rate mode-locked laser sources have enabled the development of PLS techniques that leverage coherent optical spreading and despreading, phase mask encoding, and under-the-noise transmission. Since capturing multi-THz E-fields is impractical, real-time all-optical decoding is necessary, as offline post-processing yields permanently poor performance (indicated by a negative SNR) for unauthorized detection. This paper reports the demonstrations of PLS transmission of 30 G and 60G Bauds, using QPSK and 16-QAM modulation schemes, achieved over distances of up to 100 km, with a real-time DSP ASIC. These achievements pave the way for high-bandwidth point-to-point harvest-immune optical connectivity.Introduction
The capability to form a photonic shield by using a unique all-optical transmission scheme incorporating multi-THz coherent spreading, spectral phase encoding (SPE), and negative optical signal-to-noise ratio (OSNR) completely prevents offline deciphering of captured data-in-transit. This photonic shield scheme provides an ultimate solution to the “harvest-now, decrypt later” threat by eliminating unauthorised recording. Thus, no raw data is available for any post-processing, including by quantum computers. Both the full line rate payload and the asymmetric key exchange, are transmitted through the secured channel. This work presents an industry-level demonstration, including real-time client data transmission and seamlessly continuously changing spectral phase encoding (SPE) photonic keys. A 100 Gbps DP-QPSK signal and a 200 Gbps DP-16QAM link are established over 80 km of standard single mode fiber (SSMF).
As data rates outpace the capabilities of electronic encryption schemes, photonic layer security may fill the gap in providing a communication security solution at high data rates. In this article we review and highlight the advantages of our proposed optical code-division multiplexed (OCDM)-based photonic layer security (PLS) system based on high-resolution control of the optical phase of tightly spaced phase locked laser lines. Such a PLS system is scaleable to 100 Gb/s and provides a protocol independent security solution. We review the use of high-resolution control of the optical phase of mode-locked laser frequency combs as an enabling technology for a new class of OCDM systems. A network based on such systems is compatible with and can have comparable spectral efficiency to existing DWDM networks. Through inverse multiplexing of 10 Gb/s tributaries, we have already demonstrated optical transmission of a 40 Gb/s aggregate OCDM signal over 400 km. Such a PLS solution is achieved through shared phase scrambling of the individual OCDM codes assigned to each of the tributaries using an integrated micro-ring resonator-based phase coder/scrambler. The confidentiality of OCDM-based PLS is robust against exhaustive, known plain text, and archival/forensic attacks, and can complement digital encryption operating at higher layers. Moreover, the integrity of the PLS solution is ensured through the inherent coupling to confidentiality, since knowledge of the key is needed in order to easily alter the transmitted data stream without introducing observable errors. This system can leverage advances in optical integration to support new applications where electronic encryption is impractical because of space, weight, power, availability, and cost requirements. Such applications range from timely security support for the emerging 100 GbE standards to all-optical multilevel security offered through the compatibility of PLS with transparent DWDM networks.
A novel digital signal processing (DSP)-based scheme for physical layer security in coherent optical communication systems is proposed and numerically investigated. The optical layer signal encryption is accomplished by two dispersive elements and one phase modulator (PM) driven by a DSP-generated encryption key, whilst signal decryption uses similar components but with inverted dispersion values and security keys. A critical aspect of the DSP-based physical layer security is that the security keys, driving the PMs to hide/recover the data signals, must be highly unpredictable and noise-like, thus orthogonal frequency division multiplexing (OFDM) signals are employed as they possess these characteristics, they can also be easily generated and cover a suitably wide range of unique keys. Numerical simulations are conducted to determine optimum system parameters for achieving a high level of security, the key parameters requiring optimization are the dispersion of the dispersive elements and the bandwidth of the security keys. Using these determined optimum parameters, in-depth investigations are undertaken of encryption/decryption induced transmission performance penalties, sensitives to various parameter offsets and operation over various transmission distances. To observe any data signal dependencies, various performance metrics are investigated for different combinations of modulation formats (DQPSK and 16QAM) and baud rates (40 Gbaud and 100 Gbaud) for the transmitted data signals. The proposed DSP-based physical layer security scheme is shown to have the potential to achieve, in a low-cost and highly effective manner, a high level of physical layer security with acceptable performance penalties for existing coherent optical communication systems.
Physical Layer Security (PLS) exploits characteristics and properties of the physical layer for data encryption and supplements conventional cryptography for enhanced overall security. Most of the PLS methodologies rely on the (statistical) characteristics of the transmission channel to either generate secure encryption keys, or to exploit them together with other physical layer characteristics (i.e. advanced modulation schemes) for secure transmission. However, these approaches often lead to increased complexity and therefore become impractical for actual system implementation. Recent advancements in Quantum Key Distribution (QKD) systems allow for the utilization of ultra-secure and robust high-rate key exchange. In this work, we propose and describe practical techniques for exploiting and seamlessly integrating highrate QKD keys to encrypt modulation parameters and quantities of conventional modulation schemes like M-QAM, DMT and OFDM of communication links. Moreover, we present transmission scenarios, integrating QKD-PLS in free space optics links, together with their numerical evaluation. The main advantage of QKD exploitation to the proposed solutions comes from the seamless and transparent integration and application of high-rate keys which can either be used in their original form or feed a pseudo-random number generator, to modify the modulation properties/symbols in very high rates, such that eavesdropping and decoding of the encrypted information becomes almost impossible. Additionally, we present the architecture of a real time practical system utilizing and seamlessly integrating the QKD keys into transceiver links to form a robust and ultra-secure PLS ecosystem.
This research introduces a novel physical-layer encryption technique for metropolitan-optimized optical transport networks (M-OTNs) that integrates real-time optical signal time-domain scrambling/descrambling with decoy-state quantum key distribution (DS-QKD). The method processes real-time optical data from the optical service unit (OSU) using a series of tunable Fabry–Perot cavities (FPCs), synchronized and updated with a running key. Experimental validation demonstrates secure communication within the optical network’s physical layer during standard OTU2 data transmission (10.709 Gbps), achieving an online transmission distance exceeding 100 km over typical single-mode fiber with a power loss of approximately 1.77 dB. The results indicate that this integrated approach significantly enhances the security of the optical physical layer in M-OTNs.