Abstract
Device-independent quantum key distribution (DIQKD) provides the strongest form of secure key exchange, using only the input–output statistics of the devices to achieve information-theoretic security. Although the basic security principles of DIQKD are now well understood, it remains a technical challenge to derive reliable and robust security bounds for advanced DIQKD protocols that go beyond the previous results based on violations of the CHSH inequality. In this work, we present a framework based on semidefinite programming that gives reliable lower bounds on the asymptotic secret key rate of any QKD protocol using untrusted devices. In particular, our method can in principle be utilized to find achievable secret key rates for any DIQKD protocol, based on the full input–output probability distribution or any choice of Bell inequality. Our method also extends to other DI cryptographic tasks.
Highlights
Device-independent quantum key distribution (DIQKD) considers the problem of secure key exchange using devices which are untrusted or uncharacterized[1,2,3]
While the basic principle behind the security of DIQKD is well understood from the monogamy property of nonlocal correlations[9], an explicit security analysis is rather involved and tricky
Entropy production[30,31,32,33] is a fundamental concept traditionally used to study non-equilibrium thermodynamic processes, but here we show that it has an intrinsic connection to quantum cryptography as well
Summary
Device-independent quantum key distribution (DIQKD) considers the problem of secure key exchange using devices which are untrusted or uncharacterized[1,2,3] In this setting, security is based entirely on the observation of nonlocal correlations, which are typically measured by a Bell inequality[4,5]. While the basic principle behind the security of DIQKD is well understood from the monogamy property of nonlocal correlations[9], an explicit security analysis is rather involved and tricky. This is mainly because the dimension of the underlying shared quantum state is unknown and the usual security proof techniques cannot be applied
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