Abstract
Data security plays an increasingly important role in modern telecommunications. The advent of quantum computational processors presents a significant threat to today's widely employed public key encryption algorithms, necessitating the adoption of new approaches to data encryption. Whilst quantum key distribution guarantees unconditional security for cryptographic key exchange in optical communication networks, the data rate is slow (Mbit/s), especially when compared to conventional optical communication. Here we present a highly secure encryption approach in which the encryption key, generated by quantum key distribution at a rate of up to 2.9 Mbit/s, was used to seed physical layer encryption performed using time domain spectral phase encoding (TDSPE). This allowed us to demonstrate encrypted 40 Gbit/s quadrature phase shift keyed data communications over 52.3 km of installed optical fiber, which cannot be eavesdropped using brute force computational attacks. Any attempt to eavesdrop the encrypted signal in the physical layer is highly time-sensitive – the phase states must be measured and decrypted prior to optical signal attenuation, which means that the attack procedure typically needs to be completed within a few milliseconds. This work represents the first example of quantum-enhanced physical layer encryption at realistic optical data rates that is fully secure from brute force computational attacks and the first demonstration of TDSPE using continuous-wave laser source and quadrature phase shift key modulation.
Highlights
E nsuring the security of information exchange in optical communication systems has become one of the primary challenges in telecommunication networks
The perturbation of the signal caused by an eavesdropper would result in an increase in the quantum bit error rate (QBER), which could be quantified by Alice and Bob
The time domain spectral phase encoding (TDSPE) operates with coherent quadrature phase shift keying (QPSK) modulation using CW laser source
Summary
E nsuring the security of information exchange in optical communication systems has become one of the primary challenges in telecommunication networks. We propose a new approach that employs QKD to generate and share the secure keys which seed the coding operations used in the TDSPE to scramble the signal in the physical layer. The code scrambling is able to operate bit-by-bit at a high clock rate (demonstrated from 20 GHz to 40 GHz [9] - [13]) in the TDSPE system acts as an interface between QKD and the classical optical transmission system, and enables a further improvement to the security of high-speed optical communication, compared with digital data encrypted systems. TDSPE operating with QPSK modulation using CW laser source is firstly demonstrated to provide physical layer security with full compatibility with the traditional symmetric-key encryption. The classical 40 Gbps QPSK data transmission system, using single wavelength and single polarization, transmitted data over 52.3 km of standard telecoms single-mode fiber (SMF)
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