Achieving the physical limits of the bounded-storage model

TL;DR

This paper demonstrates that secure two-party cryptography can be achieved in the bounded-storage model even when the adversary's quantum storage is larger than previously considered, by leveraging imperfections and noise in quantum memories.

Contribution

It introduces a protocol that remains secure as long as the adversary's quantum storage is limited, extending security to noisy quantum memories.

Findings

Security holds if adversary's storage is less than a small fraction of transmitted qubits

Security can be extended to noisy quantum memories

Protocol achieves security beyond previous limitations

Abstract

Secure two-party cryptography is possible if the adversary's quantum storage device suffers imperfections. For example, security can be achieved if the adversary can store strictly less then half of the qubits transmitted during the protocol. This special case is known as the bounded-storage model, and it has long been an open question whether security can still be achieved if the adversary's storage were any larger. Here, we answer this question positively and demonstrate a two-party protocol which is secure as long as the adversary cannot store even a small fraction of the transmitted pulses. We also show that security can be extended to a larger class of noisy quantum memories.