# A security proof of the round-robin differential phase shift quantum key distribution protocol based on the signal disturbance

## TL;DR

This paper provides a security proof for the RRDPS quantum key distribution protocol based on signal disturbance, revealing its unique information-disturbance trade-off and improving key rates under certain conditions.

## Contribution

It offers a novel security analysis of the RRDPS protocol using signal disturbance, connecting it with traditional QKD security proofs.

## Key findings

- Better key rates for small block lengths with low disturbance
- Limited improvement in key rate for large block lengths
- Bridges gap between RRDPS and conventional QKD protocols

## Abstract

The round-robin differential phase shift (RRDPS) quantum key distribution (QKD) protocol is a unique quantum key distribution protocol whose security has not been understood through an information-disturbance trade-off relation, and a sufficient amount of privacy amplification was given independently of signal disturbance. Here, we discuss the security of the RRDPS protocol in the asymptotic regime when a good estimate of the bit error rate is available as a measure of signal disturbance. The uniqueness of the RRDPS protocol shows up as a peculiar form of information-disturbance trade-off curve. When the length of a block of pulses used for encoding and the signal disturbance are both small, it provides a significantly better key rate than that from the original security proof. On the other hand, when the block length is large, the use of the signal disturbance makes little improvement in the key rate. Our analysis will bridge a gap between the RRDPS protocol and the conventional QKD protocols.