Abstract
Authentication provides the trust people need to engage in transactions. The advent of physical keys that are impossible to copy promises to revolutionize this field. Up to now, such keys have been verified by classical challenge-response protocols. Such protocols are in general susceptible to emulation attacks. Here we demonstrate Quantum-Secure Authentication ("QSA") of an unclonable classical physical key in a way that is inherently secure by virtue of quantum-physical principles. Our quantum-secure authentication operates in the limit of a large number of channels, represented by the more than thousand degrees of freedom of an optical wavefront shaped with a spatial light modulator. This allows us to reach quantum security with weak coherent pulses of light containing dozens of photons, too few for an adversary to determine their complex spatial shapes, thereby rigorously preventing emulation.
Highlights
Authentication of persons can be based on “something that you know,” e.g., digital keys, or “something that you have,” e.g., physical objects such as classical keys or official documents
A physical unclonable function (PUF) is a physical object that cannot feasibly be copied because its manufacture inherently contains a large number of uncontrollable degrees of freedom
A PUF is a function in the sense that it reacts to a stimulus (“challenge”) by giving a response
Summary
Authentication of persons can be based on “something that you know,” e.g., digital keys, or “something that you have,” e.g., physical objects such as classical keys or official documents. In this Letter we present quantum-secure authentication (QSA) of optical keys, a scheme with highly desirable properties. – uses a key that is infeasible to emulate physically; – is unconditionally secure against digital emulation attacks; – does not depend on secrecy of any stored data; – does not depend on unproven mathematical assumptions; and – is straightforward to implement with current technology.
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