Quantum Cryptography II: How to re-use a one-time pad safely even if P=NP

TL;DR

This paper discusses a quantum cryptographic scheme that allows safe reuse of a one-time pad multiple times, leveraging quantum uncertainty principles to detect eavesdropping without relying on computational hardness assumptions.

Contribution

It introduces a quantum communication protocol enabling secure one-time pad reuse independent of complexity-theoretic assumptions.

Findings

Quantum uncertainty allows eavesdrop detection in communication channels.

The scheme permits multiple reuse of a one-time pad without compromising security.

Part of the channel capacity can be used to refresh the one-time pad after eavesdrop detection.

Abstract

When elementary quantum systems, such as polarized photons, are used to transmit digital information, the uncertainty principle gives rise to novel cryptographic phenomena unachievable with traditional transmission media, e.g. a communications channel on which it is impossible in principle to eavesdrop without a high probability of being detected. With such a channel, a one-time pad can safely be reused many times as long as no eavesdrop is detected, and, planning ahead, part of the capacity of these uncompromised transmissions can be used to send fresh random bits with which to replace the one-time pad when an eavesdrop finally is detected. Unlike other schemes for stretching a one-time pad, this scheme does not depend on complexity-theoretic assumptions such as the difficulty of factoring.