Quantum bit commitment and unconditional security

TL;DR

This paper challenges the prevailing belief that unconditionally secure quantum bit commitment is impossible by identifying gaps in the proof and presenting new protocols that achieve unconditional security.

Contribution

It introduces novel quantum bit commitment protocols based on two-way communication and demonstrates at least one unconditionally secure protocol, addressing gaps in prior impossibility proofs.

Findings

Counterexamples to the impossibility proof are provided.

Four new protocol types are constructed with innovative techniques.

A specific protocol is proven unconditionally secure.

Abstract

It is generally believed that unconditionally secure quantum bit commitment is impossible, due to widespread acceptance of an impossibility proof that utilizes quantum entaglement cheating. In this paper, we delineate how the impossibiliy proof formulation misses various types of quantum bit commitment protocols based on two-way quantum communications. We point out some of the gaps in the impossibility proof reasoning, and present corresponding counterexamples. Four different types of bit commitment protocols are constructed with several new protocol techniques. A specific Type 4 protocol is described and proved unconditionally secure. Security analysis of a Type 1 protocol and a Type 2 protocol are also sketched. The security of Type 3 protocols is as yet open. A development of quantum statistical decision theory and quantum games is needed to provie a complete security analysis of many such protocols.