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Documents authored by Broadbent, Anne

Document
DOI: 10.4230/LIPIcs.ITCS.2023.28
Rigidity for Monogamy-Of-Entanglement Games

Authors: Anne Broadbent and Eric Culf

Published in: LIPIcs, Volume 251, 14th Innovations in Theoretical Computer Science Conference (ITCS 2023)

Abstract
In a monogamy-of-entanglement (MoE) game, two players who do not communicate try to simultaneously guess a referee’s measurement outcome on a shared quantum state they prepared. We study the prototypical example of a game where the referee measures in either the computational or Hadamard basis and informs the players of her choice. We show that this game satisfies a rigidity property similar to what is known for some nonlocal games. That is, in order to win optimally, the players' strategy must be of a specific form, namely a convex combination of four unentangled optimal strategies generated by the Breidbart state. We extend this to show that strategies that win near-optimally must also be near an optimal state of this form. We also show rigidity for multiple copies of the game played in parallel. We give three applications: (1) We construct for the first time a weak string erasure (WSE) scheme where the security does not rely on limitations on the parties' hardware. Instead, we add a prover, which enables security via the rigidity of this MoE game. (2) We show that the WSE scheme can be used to achieve bit commitment in a model where it is impossible classically. (3) We achieve everlasting-secure randomness expansion in the model of trusted but leaky measurement and untrusted preparation and measurements by two isolated devices, while relying only on the temporary assumption of pseudorandom functions. This achieves randomness expansion without the need for shared entanglement.
Cite as

Anne Broadbent and Eric Culf. Rigidity for Monogamy-Of-Entanglement Games. In 14th Innovations in Theoretical Computer Science Conference (ITCS 2023). Leibniz International Proceedings in Informatics (LIPIcs), Volume 251, pp. 28:1-28:29, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)

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@InProceedings{broadbent_et_al:LIPIcs.ITCS.2023.28,
  author =	{Broadbent, Anne and Culf, Eric},
  title =	{{Rigidity for Monogamy-Of-Entanglement Games}},
  booktitle =	{14th Innovations in Theoretical Computer Science Conference (ITCS 2023)},
  pages =	{28:1--28:29},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-263-1},
  ISSN =	{1868-8969},
  year =	{2023},
  volume =	{251},
  editor =	{Tauman Kalai, Yael},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.ITCS.2023.28},
  URN =		{urn:nbn:de:0030-drops-175319},
  doi =		{10.4230/LIPIcs.ITCS.2023.28},
  annote =	{Keywords: Rigidity, Self-Testing Monogamy-of-Entanglement Games, Bit Commitment, Randomness Expansion}
}
Document
DOI: 10.4230/LIPIcs.TQC.2020.4
Uncloneable Quantum Encryption via Oracles

Authors: Anne Broadbent and Sébastien Lord

Published in: LIPIcs, Volume 158, 15th Conference on the Theory of Quantum Computation, Communication and Cryptography (TQC 2020)

Abstract
Quantum information is well known to achieve cryptographic feats that are unattainable using classical information alone. Here, we add to this repertoire by introducing a new cryptographic functionality called uncloneable encryption. This functionality allows the encryption of a classical message such that two collaborating but isolated adversaries are prevented from simultaneously recovering the message, even when the encryption key is revealed. Clearly, such functionality is unattainable using classical information alone. We formally define uncloneable encryption, and show how to achieve it using Wiesner’s conjugate coding, combined with a quantum-secure pseudorandom function (qPRF). Modelling the qPRF as an oracle, we show security by adapting techniques from the quantum one-way-to-hiding lemma, as well as using bounds from quantum monogamy-of-entanglement games.
Cite as

Anne Broadbent and Sébastien Lord. Uncloneable Quantum Encryption via Oracles. In 15th Conference on the Theory of Quantum Computation, Communication and Cryptography (TQC 2020). Leibniz International Proceedings in Informatics (LIPIcs), Volume 158, pp. 4:1-4:22, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)

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@InProceedings{broadbent_et_al:LIPIcs.TQC.2020.4,
  author =	{Broadbent, Anne and Lord, S\'{e}bastien},
  title =	{{Uncloneable Quantum Encryption via Oracles}},
  booktitle =	{15th Conference on the Theory of Quantum Computation, Communication and Cryptography (TQC 2020)},
  pages =	{4:1--4:22},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-146-7},
  ISSN =	{1868-8969},
  year =	{2020},
  volume =	{158},
  editor =	{Flammia, Steven T.},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.TQC.2020.4},
  URN =		{urn:nbn:de:0030-drops-120639},
  doi =		{10.4230/LIPIcs.TQC.2020.4},
  annote =	{Keywords: Quantum Cryptography, Symmetric Key, Monogamy-of-Entanglement}
}
Document
DOI: 10.4230/LIPIcs.TQC.2020.6
Towards Quantum One-Time Memories from Stateless Hardware

Authors: Anne Broadbent, Sevag Gharibian, and Hong-Sheng Zhou

Published in: LIPIcs, Volume 158, 15th Conference on the Theory of Quantum Computation, Communication and Cryptography (TQC 2020)

Abstract
A central tenet of theoretical cryptography is the study of the minimal assumptions required to implement a given cryptographic primitive. One such primitive is the one-time memory (OTM), introduced by Goldwasser, Kalai, and Rothblum [CRYPTO 2008], which is a classical functionality modeled after a non-interactive 1-out-of-2 oblivious transfer, and which is complete for one-time classical and quantum programs. It is known that secure OTMs do not exist in the standard model in both the classical and quantum settings. Here, we propose a scheme for using quantum information, together with the assumption of stateless (i.e., reusable) hardware tokens, to build statistically secure OTMs. Via the semidefinite programming-based quantum games framework of Gutoski and Watrous [STOC 2007], we prove security for a malicious receiver, against a linear number of adaptive queries to the token, in the quantum universal composability framework, but leave open the question of security against a polynomial amount of queries. Compared to alternative schemes derived from the literature on quantum money, our scheme is technologically simple since it is of the "prepare-and-measure" type. We also show our scheme is "tight" according to two scenarios.
Cite as

Anne Broadbent, Sevag Gharibian, and Hong-Sheng Zhou. Towards Quantum One-Time Memories from Stateless Hardware. In 15th Conference on the Theory of Quantum Computation, Communication and Cryptography (TQC 2020). Leibniz International Proceedings in Informatics (LIPIcs), Volume 158, pp. 6:1-6:25, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)

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@InProceedings{broadbent_et_al:LIPIcs.TQC.2020.6,
  author =	{Broadbent, Anne and Gharibian, Sevag and Zhou, Hong-Sheng},
  title =	{{Towards Quantum One-Time Memories from Stateless Hardware}},
  booktitle =	{15th Conference on the Theory of Quantum Computation, Communication and Cryptography (TQC 2020)},
  pages =	{6:1--6:25},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-146-7},
  ISSN =	{1868-8969},
  year =	{2020},
  volume =	{158},
  editor =	{Flammia, Steven T.},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.TQC.2020.6},
  URN =		{urn:nbn:de:0030-drops-120654},
  doi =		{10.4230/LIPIcs.TQC.2020.6},
  annote =	{Keywords: quantum cryptography, one-time memories, semi-definite programming}
}
Document
Complete Volume
DOI: 10.4230/LIPIcs.TQC.2016
LIPIcs, Volume 61, TQC'16, Complete Volume

Authors: Anne Broadbent

Published in: LIPIcs, Volume 61, 11th Conference on the Theory of Quantum Computation, Communication and Cryptography (TQC 2016)

Abstract
LIPIcs, Volume 61, TQC'16, Complete Volume
Cite as

11th Conference on the Theory of Quantum Computation, Communication and Cryptography (TQC 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 61, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2016)

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@Proceedings{broadbent:LIPIcs.TQC.2016,
  title =	{{LIPIcs, Volume 61, TQC'16, Complete Volume}},
  booktitle =	{11th Conference on the Theory of Quantum Computation, Communication and Cryptography (TQC 2016)},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-019-4},
  ISSN =	{1868-8969},
  year =	{2016},
  volume =	{61},
  editor =	{Broadbent, Anne},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.TQC.2016},
  URN =		{urn:nbn:de:0030-drops-66984},
  doi =		{10.4230/LIPIcs.TQC.2016},
  annote =	{Keywords: Data Encryption, Coding and Information Theory, Theory of Computation}
}
Document
Front Matter
DOI: 10.4230/LIPIcs.TQC.2016.0
Front Matter, Table of Contents, Preface, List of Contributed Talks, Conference Organization

Authors: Anne Broadbent

Published in: LIPIcs, Volume 61, 11th Conference on the Theory of Quantum Computation, Communication and Cryptography (TQC 2016)

Abstract
Front Matter, Table of Contents, Preface, List of Contributed Talks, Conference Organization
Cite as

11th Conference on the Theory of Quantum Computation, Communication and Cryptography (TQC 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 61, pp. 0:i-0:xii, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2016)

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@InProceedings{broadbent:LIPIcs.TQC.2016.0,
  author =	{Broadbent, Anne},
  title =	{{Front Matter, Table of Contents, Preface, List of Contributed Talks, Conference Organization}},
  booktitle =	{11th Conference on the Theory of Quantum Computation, Communication and Cryptography (TQC 2016)},
  pages =	{0:i--0:xii},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-019-4},
  ISSN =	{1868-8969},
  year =	{2016},
  volume =	{61},
  editor =	{Broadbent, Anne},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.TQC.2016.0},
  URN =		{urn:nbn:de:0030-drops-66816},
  doi =		{10.4230/LIPIcs.TQC.2016.0},
  annote =	{Keywords: Front Matter, Table of Contents, Preface, List of Contributed Talks, Conference Organization}
}
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