Experimental Side Channel Analysis of BB84 QKD Source

TL;DR

This paper experimentally analyzes the side channel vulnerabilities in BB84 quantum key distribution sources, characterizing laser diode mismatches and proposing methods to mitigate information leakage to eavesdroppers.

Contribution

It provides a detailed experimental characterization of laser diode mismatches in BB84 QKD sources and suggests mitigation strategies for side channel attacks.

Findings

Laser diodes exhibit measurable spectral, temporal, and polarization mismatches.

Mismatch parameters can lead to information leakage through side channels.

Proposed mitigation techniques reduce potential eavesdropper information gain.

Abstract

A typical implementation of BB84 protocol for quantum communication uses four laser diodes for transmitting weak coherent pulses, which may not have the same characteristics. We have characterized these lasers for mismatch in various parameters such as spectral width, pulse width, spatial mode, peak wavelength, polarization and their arrival times at the receiver. This information is utilized to calculate possible information leakage through side channel attacks by evaluating mutual information between source and eavesdropper. Based on our experimental observations of cross correlation between parameter values for different laser diodes, we suggest ways to reduce information leakage to Eve.