Eavesdropping in Semiquantum Key Distribution Protocol

TL;DR

This paper analyzes an eavesdropping strategy in semiquantum key distribution, showing that a two-way attack can extract more information than traditional one-way methods at the same disturbance level.

Contribution

It introduces a two-way eavesdropping strategy for semiquantum key distribution and demonstrates its effectiveness over one-way eavesdropping in BB84.

Findings

Two-way eavesdropping yields more information at the same disturbance level.

Eavesdropping strategy exploits the bidirectional nature of the protocol.

Enhanced eavesdropping can compromise security of semiquantum key distribution.

Abstract

In semiquantum key-distribution (Boyer et al.) Alice has the same capability as in BB84 protocol, but Bob can measure and prepare qubits only in $\{|0\rangle, |1\rangle\}$ basis and reflect any other qubit. We study an eavesdropping strategy on this scheme that listens to the channel in both the directions. With the same level of disturbance induced in the channel, Eve can extract more information using our two-way strategy than what can be obtained by the direct application of one-way eavesdropping in BB84.