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arXiv · 1501.01549

Quantifying the Leakage of Quantum Protocols for Classical Two-Party Cryptography

Louis Salvail·Christian Schaffner·Miroslava Sotakova
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Abstract

We study quantum protocols among two distrustful parties. By adopting a rather strict definition of correctness - guaranteeing that honest players obtain their correct outcomes only - we can show that every strictly correct quantum protocol implementing a non-trivial classical primitive necessarily leaks information to a dishonest player. This extends known impossibility results to all non-trivial primitives. We provide a framework for quantifying this leakage and argue that leakage is a good measure for the privacy provided to the players by a given protocol. Our framework also covers the case where the two players are helped by a trusted third party. We show that despite the help of a trusted third party, the players cannot amplify the cryptographic power of any primitive. All our results hold even against quantum honest-but-curious adversaries who honestly follow the protocol but purify their actions and apply a different measurement at the end of the protocol. As concrete examples, we establish lower bounds on the leakage of standard universal two-party primitives such as oblivious transfer.

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Louis Salvail, Christian Schaffner, Miroslava Sotakova. 2015-01-07. Quantifying the Leakage of Quantum Protocols for Classical Two-Party Cryptography. https://doi.org/10.1142/s0219749914500415

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