Satellite Quantum Communications When Man-in-the-Middle Attacks Are Excluded.

Tom Vergoossen,Alexander Ling,Robert Bedington,James A Grieve

doi:10.3390/e21040387

Tom Vergoossen, Alexander Ling + Show 2 more

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https://doi.org/10.3390/e21040387

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Abstract

An application of quantum communications is the transmission of qubits to create shared symmetric encryption keys in a process called quantum key distribution (QKD). Contrary to public-private key encryption, symmetric encryption is considered safe from (quantum) computing attacks, i.e., it provides forward security and is thus attractive for secure communications. In this paper we argue that for free-space quantum communications, especially with satellites, if one assumes that man-in-the-middle attacks can be detected by classical channel monitoring techniques, simplified quantum communications protocols and hardware systems can be implemented that offer improved key rates. We term these protocols photon key distribution (PKD) to differentiate them from the standard QKD protocols. We identify three types of photon sources and calculate asymptotic secret key rates for PKD protocols and compare them to their QKD counterparts. PKD protocols use only one measurement basis which we show roughly doubles the key rates. Furthermore, with the relaxed security assumptions one can establish keys at very high losses, in contrast to QKD where at the same losses privacy amplification would make key generation impossible.

Highlights

Cryptographic key distribution is a major application of quantum communication
Our exploration of photon key distribution (PKD) here builds on the ideas put forward by Sasaki et al In this paper we look at the asymptotic secret key rates at high losses for three quantum key distribution (QKD) schemes using three different kinds of transmitter hardware, and compare this to three simplified PKD schemes that use similar hardware
This does not happen in the PKD equivalents as it is assumed that there are no active man-in-the-middle attacks, and so privacy amplification is only required for multi-photon pulses

Summary

Introduction

Cryptographic key distribution is a major application of quantum communication. Such schemes typically use measurements of quantum states of photons shared between two remote parties to allow both sides to derive shared entropy that can be quantitatively assessed to be private. This shared entropy may be used as keying material for use as one time pads [1] or as seed keys for symmetric encryption [2]. For quantum communication from satellites, and other moving platforms, photons are distributed using free space optics (FSO)

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