Improving the Security of Quantum Protocols via Commit-and-Open

TL;DR

This paper introduces a compiler that enhances the security of two-party quantum protocols, making them secure against general quantum adversaries while preserving efficiency and applicability to protocols like identification and oblivious transfer.

Contribution

The paper presents a general compiler that boosts security of quantum protocols from almost honest security to full quantum security, preserving efficiency and applicable to various protocols.

Findings

Compiler extends security to arbitrary quantum adversaries.

Security preserved in bounded-quantum-storage model.

Applicable to quantum identification and oblivious transfer.

Abstract

We consider two-party quantum protocols starting with a transmission of some random BB84 qubits followed by classical messages. We show a general "compiler" improving the security of such protocols: if the original protocol is secure against an "almost honest" adversary, then the compiled protocol is secure against an arbitrary computationally bounded (quantum) adversary. The compilation preserves the number of qubits sent and the number of rounds up to a constant factor. The compiler also preserves security in the bounded-quantum-storage model (BQSM), so if the original protocol was BQSM-secure, the compiled protocol can only be broken by an adversary who has large quantum memory and large computing power. This is in contrast to known BQSM-secure protocols, where security breaks down completely if the adversary has larger quantum memory than expected. We show how our technique can be applied to quantum identification and oblivious transfer protocols.