IF-Over-Fiber Transmission of OFDM Quantum-Noise Randomized PSK Cipher for Physical Layer Encryption of Wireless Signals

Ken Tanizawa,Fumio Futami

doi:10.1109/jlt.2021.3119603

Abstract

This study proposes an intensity modulation/direct detection intermediate frequency-over-fiber (IFoF) system that generates a microwave orthogonal frequency-division multiplexing (OFDM) quantum-noise randomized phase-shift-keying (PSK) cipher. The system directly prevents wireless interception by an eavesdropper without a private key. We theoretically analyze the system and derive a fundamental tradeoff between the security and signal quality at an intermediate frequency (IF). The system achieves balanced security and signal quality. We experimentally demonstrate 4.09-Gbit/s PSK cipher generation at an IF of 3.6 GHz. The cipher has 2 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">16</sup> phase levels, and more than 100 adjacent signals are masked by quantum noise. The quantum-noise signal masking imposes irreducible uncertainty on illegitimate reception of the cipher, and a symbol error ratio (SER) that an eavesdropper can reach approaches 1. A lower bound of the SER is promised because truly random signal masking by quantum noise cannot be reduced. The error vector magnitude of the IF signals after decryption is maintained at a low value for wireless transmission. The cipher directly and effectively protects the wireless transmission of personal data from interception.

Highlights

A variety of services and applications that require the exchange of personal information are widely available via the Internet
This paper reported an IM/DD intermediate frequency-over-fiber (IFoF) system that generated an orthogonal frequency-division multiplexing (OFDM) quantum-noise randomized PSK cipher for security against wireless interception
Theoretical study showed that the tradeoff between the security and signal quality was mitigated by increasing the order of PSK after the encryption

Summary

INTRODUCTION

A variety of services and applications that require the exchange of personal information are widely available via the Internet. The security policy ensures that an illegitimate receiver or eavesdropper cannot obtain full digital information from the signal reception, and interception is prevented before the cryptanalysis of conventional ciphers. PLE that utilizes signal masking by quantum (shot) noise has been proposed and demonstrated for fiber-optic transmission [6]–[11]. IM/DD IFoF transmission of OFDM PSK signals with 216 phase levels over a short fiber link and the successful generation of a 4.09 Gbit/s quantum-noise randomized PSK cipher at an IF of 3.6 GHz are experimentally demonstrated. Theoretical analysis shows that more than 100 signal levels are masked by quantum noise in the experiments, leading a high symbol error ratio (SER) of higher than 0.99 for an eavesdropper. The cipher directly and effectively protects wireless transmission from interception

System Configuration

Analysis of Quantum-Noise Signal Masking

Security against Interception

EXPERIMENTS

CONCLUSIONS