2 Search Results for "Dujmovic, Jesko"

Document
DOI: 10.4230/LIPIcs.ITC.2022.4
Maliciously Circuit-Private FHE from Information-Theoretic Principles

Authors: Nico Döttling and Jesko Dujmovic

Published in: LIPIcs, Volume 230, 3rd Conference on Information-Theoretic Cryptography (ITC 2022)

Abstract
Fully homomorphic encryption (FHE) allows arbitrary computations on encrypted data. The standard security requirement, IND-CPA security, ensures that the encrypted data remain private. However, it does not guarantee privacy for the computation performed on the encrypted data. Statistical circuit privacy offers a strong privacy guarantee for the computation process, namely that a homomorphically evaluated ciphertext does not leak any information on how the result of the computation was obtained. Malicious statistical circuit privacy requires this to hold even for maliciously generated keys and ciphertexts. Ostrovsky, Paskin and Paskin (CRYPTO 2014) constructed an FHE scheme achieving malicious statistical circuit privacy. Their construction, however, makes non-black-box use of a specific underlying FHE scheme, resulting in a circuit-private scheme with inherently high overhead. This work presents a conceptually different construction of maliciously circuit-private FHE from simple information-theoretical principles. Furthermore, our construction only makes black-box use of the underlying FHE scheme, opening the possibility of achieving practically efficient schemes. Finally, in contrast to the OPP scheme in our scheme, pre- and post-homomorphic ciphertexts are syntactically the same, enabling new applications in multi-hop settings.
Cite as

Nico Döttling and Jesko Dujmovic. Maliciously Circuit-Private FHE from Information-Theoretic Principles. In 3rd Conference on Information-Theoretic Cryptography (ITC 2022). Leibniz International Proceedings in Informatics (LIPIcs), Volume 230, pp. 4:1-4:21, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)

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@InProceedings{dottling_et_al:LIPIcs.ITC.2022.4,
  author =	{D\"{o}ttling, Nico and Dujmovic, Jesko},
  title =	{{Maliciously Circuit-Private FHE from Information-Theoretic Principles}},
  booktitle =	{3rd Conference on Information-Theoretic Cryptography (ITC 2022)},
  pages =	{4:1--4:21},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-238-9},
  ISSN =	{1868-8969},
  year =	{2022},
  volume =	{230},
  editor =	{Dachman-Soled, Dana},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.ITC.2022.4},
  URN =		{urn:nbn:de:0030-drops-164826},
  doi =		{10.4230/LIPIcs.ITC.2022.4},
  annote =	{Keywords: Fully Homomorphic Encryption, FHE, Homomorphic Encryption, Oblivious Transfer, Malicious Statistical Circuit Privacy, Multi-Hop, Information Theory, Cryptography}
}
Document
DOI: 10.4230/LIPIcs.ITCS.2022.2
Algebraic Restriction Codes and Their Applications

Authors: Divesh Aggarwal, Nico Döttling, Jesko Dujmovic, Mohammad Hajiabadi, Giulio Malavolta, and Maciej Obremski

Published in: LIPIcs, Volume 215, 13th Innovations in Theoretical Computer Science Conference (ITCS 2022)

Abstract
Consider the following problem: You have a device that is supposed to compute a linear combination of its inputs, which are taken from some finite field. However, the device may be faulty and compute arbitrary functions of its inputs. Is it possible to encode the inputs in such a way that only linear functions can be evaluated over the encodings? I.e., learning an arbitrary function of the encodings will not reveal more information about the inputs than a linear combination. In this work, we introduce the notion of algebraic restriction codes (AR codes), which constrain adversaries who might compute any function to computing a linear function. Our main result is an information-theoretic construction AR codes that restrict any class of function with a bounded number of output bits to linear functions. Our construction relies on a seed which is not provided to the adversary. While interesting and natural on its own, we show an application of this notion in cryptography. In particular, we show that AR codes lead to the first construction of rate-1 oblivious transfer with statistical sender security from the Decisional Diffie-Hellman assumption, and the first-ever construction that makes black-box use of cryptography. Previously, such protocols were known only from the LWE assumption, using non-black-box cryptographic techniques. We expect our new notion of AR codes to find further applications, e.g., in the context of non-malleability, in the future.
Cite as

Divesh Aggarwal, Nico Döttling, Jesko Dujmovic, Mohammad Hajiabadi, Giulio Malavolta, and Maciej Obremski. Algebraic Restriction Codes and Their Applications. In 13th Innovations in Theoretical Computer Science Conference (ITCS 2022). Leibniz International Proceedings in Informatics (LIPIcs), Volume 215, pp. 2:1-2:15, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)

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@InProceedings{aggarwal_et_al:LIPIcs.ITCS.2022.2,
  author =	{Aggarwal, Divesh and D\"{o}ttling, Nico and Dujmovic, Jesko and Hajiabadi, Mohammad and Malavolta, Giulio and Obremski, Maciej},
  title =	{{Algebraic Restriction Codes and Their Applications}},
  booktitle =	{13th Innovations in Theoretical Computer Science Conference (ITCS 2022)},
  pages =	{2:1--2:15},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-217-4},
  ISSN =	{1868-8969},
  year =	{2022},
  volume =	{215},
  editor =	{Braverman, Mark},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.ITCS.2022.2},
  URN =		{urn:nbn:de:0030-drops-155987},
  doi =		{10.4230/LIPIcs.ITCS.2022.2},
  annote =	{Keywords: Algebraic Restriction Codes, Oblivious Transfer, Rate 1, Statistically Sender Private, OT, Diffie-Hellman, DDH}
}
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