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Fidelity of Quantum Strategies with Applications to Cryptography Gutoski, Gus Rosmanis, Ansis Sikora, Jamie Quantum strategies cryptography fidelity semidefinite programming We introduce a definition of the fidelity function for multi-round quantum strategies, which we call the strategy fidelity, that is a generalization of the fidelity function for quantum states. We provide many interesting properties of the strategy fidelity including a Fuchs-van de Graaf relationship with the strategy norm. We illustrate an operational interpretation of the strategy fidelity in the spirit of Uhlmann's Theorem and discuss its application to the security analysis of quantum protocols for interactive cryptographic tasks such as bit-commitment and oblivious string transfer. Our analysis is very general in the sense that the actions of the protocol need not be fully specified, which is in stark contrast to most other security proofs. Lastly, we provide a semidefinite programming formulation of the strategy fidelity. Schloss Dagstuhl – Leibniz-Zentrum für Informatik Gus Gutoski and Ansis Rosmanis and Jamie Sikora 2018 Is Part Of LIPIcs, Volume 73, 12th Conference on the Theory of Quantum Computation, Communication and Cryptography (TQC 2017) InProceedings Text doc-type:ResearchArticle publishedVersion application/pdf doi:10.4230/LIPIcs.TQC.2017.8 urn:nbn:de:0030-drops-85830 https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.TQC.2017.8 eng https://creativecommons.org/licenses/by/3.0/legalcode