Unconditionally secured classical cryptography using quantum superposition and unitary transformation

Byoung S Ham

doi:10.1038/s41598-020-68038-7

Abstract

Over decades quantum cryptography has been intensively studied for unconditionally secured key distribution in a quantum regime. Due to the quantum loopholes caused by imperfect single photon detectors and/or lossy quantum channels, however, the quantum cryptography is practically inefficient and even vulnerable to eavesdropping. Here, a method of unconditionally secured key distribution potentially compatible with current fiber-optic communications networks is proposed in a classical regime for high-speed optical backbone networks. The unconditional security is due to the quantum superposition-caused measurement indistinguishability between paired transmission channels and its unitary transformation resulting in deterministic randomness corresponding to the no-cloning theorem in a quantum key distribution protocol.

Highlights

Over decades quantum cryptography has been intensively studied for unconditionally secured key distribution in a quantum regime
Compared with nonorthogonal bases in Quantum key distribution (QKD) resulting in randomness according to the Heisenberg’s uncertainty principle, the orthogonal bases in the proposed classical cryptography play the same role of the randomness in a classical regime
The basic physics of unconditional security in the proposed classical cryptography lies in the quantum superposition between noncanonical variables in Mach–Zehnder interferometer (MZI), corresponding to the no-cloning theorem in QKD, where the no-cloning theorem originates in Schrodinger’s uncertainty principle with canonical variables

Summary

Introduction

Over decades quantum cryptography has been intensively studied for unconditionally secured key distribution in a quantum regime. As a physical infrastructure of the proposed unconditionally secured classical cryptography, an MZI scheme is used for the real transmission lines to realize both randomness-based key generation and unconditionally safe distribution via quantum superposition and unitary transformation

Results

Conclusion