Volume

LIPIcs, Volume 304

5th Conference on Information-Theoretic Cryptography (ITC 2024)

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Event

ITC 2024, August 14-16, 2024, Stanford, CA, USA

Editor

Divesh Aggarwal
  • National University of Singapore, Singapore

Publication Details

  • published at: 2024-08-06
  • Publisher: Schloss Dagstuhl – Leibniz-Zentrum für Informatik
  • ISBN: 978-3-95977-333-1
  • DBLP: db/conf/icits/itc2024

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Document
Complete Volume
DOI: 10.4230/LIPIcs.ITC.2024
LIPIcs, Volume 304, ITC 2024, Complete Volume

Authors: Divesh Aggarwal

Abstract
LIPIcs, Volume 304, ITC 2024, Complete Volume
Cite as

5th Conference on Information-Theoretic Cryptography (ITC 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 304, pp. 1-232, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@Proceedings{aggarwal:LIPIcs.ITC.2024,
  title =	{{LIPIcs, Volume 304, ITC 2024, Complete Volume}},
  booktitle =	{5th Conference on Information-Theoretic Cryptography (ITC 2024)},
  pages =	{1--232},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-333-1},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{304},
  editor =	{Aggarwal, Divesh},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ITC.2024},
  URN =		{urn:nbn:de:0030-drops-205075},
  doi =		{10.4230/LIPIcs.ITC.2024},
  annote =	{Keywords: LIPIcs, Volume 304, ITC 2024, Complete Volume}
}
Document
Front Matter
DOI: 10.4230/LIPIcs.ITC.2024.0
Front Matter, Table of Contents, Preface, Conference Organization

Authors: Divesh Aggarwal

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

5th Conference on Information-Theoretic Cryptography (ITC 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 304, pp. 0:i-0:xii, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{aggarwal:LIPIcs.ITC.2024.0,
  author =	{Aggarwal, Divesh},
  title =	{{Front Matter, Table of Contents, Preface, Conference Organization}},
  booktitle =	{5th Conference on Information-Theoretic Cryptography (ITC 2024)},
  pages =	{0:i--0:xii},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-333-1},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{304},
  editor =	{Aggarwal, Divesh},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ITC.2024.0},
  URN =		{urn:nbn:de:0030-drops-205087},
  doi =		{10.4230/LIPIcs.ITC.2024.0},
  annote =	{Keywords: Front Matter, Table of Contents, Preface, Conference Organization}
}
Document
DOI: 10.4230/LIPIcs.ITC.2024.1
Information-Theoretic Topology-Hiding Broadcast: Wheels, Stars, Friendship, and Beyond

Authors: D'or Banoun, Elette Boyle, and Ran Cohen

Abstract
Topology-hiding broadcast (THB) enables parties communicating over an incomplete network to broadcast messages while hiding the network topology from within a given class of graphs. Although broadcast is a privacy-free task, it is known that THB for certain graph classes necessitates computational assumptions, even against "honest but curious" adversaries, and even given a single corrupted party. Recent works have tried to understand when THB can be obtained with information-theoretic (IT) security (without cryptography or setup assumptions) as a function of properties of the corresponding graph class. We revisit this question through a case study of the class of wheel graphs and their subgraphs. The nth wheel graph is established by connecting n nodes who form a cycle with another "center" node, thus providing a natural extension that captures and enriches previously studied graph classes in the setting of IT-THB. We present a series of new findings in this line. We fully characterize feasibility of IT-THB for any class of subgraphs of the wheel, each possessing an embedded star (i.e., a well-defined center connected to all other nodes). Our characterization provides evidence that IT-THB feasibility may correlate with a more fine-grained degree structure - as opposed to pure connectivity - of the corresponding graphs. We provide positive results achieving perfect IT-THB for new graph classes, including ones where the number of nodes is unknown. Further, we provide the first feasibility of IT-THB on non-degenerate graph-classes with t > 1 corruptions, for the class of friendship graphs (Erdös, Rényi, Sós '66).
Cite as

D'or Banoun, Elette Boyle, and Ran Cohen. Information-Theoretic Topology-Hiding Broadcast: Wheels, Stars, Friendship, and Beyond. In 5th Conference on Information-Theoretic Cryptography (ITC 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 304, pp. 1:1-1:13, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{banoun_et_al:LIPIcs.ITC.2024.1,
  author =	{Banoun, D'or and Boyle, Elette and Cohen, Ran},
  title =	{{Information-Theoretic Topology-Hiding Broadcast: Wheels, Stars, Friendship, and Beyond}},
  booktitle =	{5th Conference on Information-Theoretic Cryptography (ITC 2024)},
  pages =	{1:1--1:13},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-333-1},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{304},
  editor =	{Aggarwal, Divesh},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ITC.2024.1},
  URN =		{urn:nbn:de:0030-drops-205090},
  doi =		{10.4230/LIPIcs.ITC.2024.1},
  annote =	{Keywords: broadcast, topology-hiding protocols, information-theoretic security}
}
Document
DOI: 10.4230/LIPIcs.ITC.2024.2
Communication Complexity vs Randomness Complexity in Interactive Proofs

Authors: Benny Applebaum, Kaartik Bhushan, and Manoj Prabhakaran

Abstract
In this work, we study the interplay between the communication from a verifier in a general private-coin interactive protocol and the number of random bits it uses in the protocol. Under worst-case derandomization assumptions, we show that it is possible to transform any I-round interactive protocol that uses ρ random bits into another one for the same problem with the additional property that the verifier’s communication is bounded by O(I⋅ ρ). Importantly, this is done with a minor, logarithmic, increase in the communication from the prover to the verifier and while preserving the randomness complexity. Along the way, we introduce a new compression game between computationally-bounded compressor and computationally-unbounded decompressor and a new notion of conditioned efficient distributions that may be of independent interest. Our solutions are based on a combination of perfect hashing and pseudorandom generators.
Cite as

Benny Applebaum, Kaartik Bhushan, and Manoj Prabhakaran. Communication Complexity vs Randomness Complexity in Interactive Proofs. In 5th Conference on Information-Theoretic Cryptography (ITC 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 304, pp. 2:1-2:16, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{applebaum_et_al:LIPIcs.ITC.2024.2,
  author =	{Applebaum, Benny and Bhushan, Kaartik and Prabhakaran, Manoj},
  title =	{{Communication Complexity vs Randomness Complexity in Interactive Proofs}},
  booktitle =	{5th Conference on Information-Theoretic Cryptography (ITC 2024)},
  pages =	{2:1--2:16},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-333-1},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{304},
  editor =	{Aggarwal, Divesh},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ITC.2024.2},
  URN =		{urn:nbn:de:0030-drops-205103},
  doi =		{10.4230/LIPIcs.ITC.2024.2},
  annote =	{Keywords: Interactive Proof Systems, Communication Complexity, Hash Functions, Pseudo-Random Generators, Compression}
}
Document
DOI: 10.4230/LIPIcs.ITC.2024.3
Are Your Keys Protected? Time Will Tell

Authors: Yoav Ben Dov, Liron David, Moni Naor, and Elad Tzalik

Abstract
Side channel attacks, and in particular timing attacks, are a fundamental obstacle to obtaining secure implementation of algorithms and cryptographic protocols, and have been widely researched for decades. While cryptographic definitions for the security of cryptographic systems have been well established for decades, none of these accepted definitions take into account the running time information leaked from executing the system. In this work, we give the foundation of new cryptographic definitions for cryptographic systems that take into account information about their leaked running time, focusing mainly on keyed functions such as signature and encryption schemes. Specifically, [(1)] 1) We define several cryptographic properties to express the claim that the timing information does not help an adversary to extract sensitive information, e.g. the key or the queries made. We highlight the definition of key-obliviousness, which means that an adversary cannot tell whether it received the timing of the queries with the actual key or the timing of the same queries with a random key. 2) We present a construction of key-oblivious pseudorandom permutations on a small or medium-sized domain. This construction is not "fixed-time," and at the same time is secure against any number of queries even in case the adversary knows the running time exactly. Our construction, which we call Janus Sometimes Recurse, is a variant of the "Sometimes Recurse" shuffle by Morris and Rogaway. 3) We suggest a new security notion for keyed functions, called noticeable security, and prove that cryptographic schemes that have noticeable security remain secure even when the exact timings are leaked, provided the implementation is key-oblivious. We show that our notion applies to cryptographic signatures, private key encryption and PRPs.
Cite as

Yoav Ben Dov, Liron David, Moni Naor, and Elad Tzalik. Are Your Keys Protected? Time Will Tell. In 5th Conference on Information-Theoretic Cryptography (ITC 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 304, pp. 3:1-3:28, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{bendov_et_al:LIPIcs.ITC.2024.3,
  author =	{Ben Dov, Yoav and David, Liron and Naor, Moni and Tzalik, Elad},
  title =	{{Are Your Keys Protected? Time Will Tell}},
  booktitle =	{5th Conference on Information-Theoretic Cryptography (ITC 2024)},
  pages =	{3:1--3:28},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-333-1},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{304},
  editor =	{Aggarwal, Divesh},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ITC.2024.3},
  URN =		{urn:nbn:de:0030-drops-205119},
  doi =		{10.4230/LIPIcs.ITC.2024.3},
  annote =	{Keywords: Side channel attacks, Timing attacks, Keyed functions, Key oblivious, Noticeable security}
}
Document
DOI: 10.4230/LIPIcs.ITC.2024.4
Pure-DP Aggregation in the Shuffle Model: Error-Optimal and Communication-Efficient

Authors: Badih Ghazi, Ravi Kumar, and Pasin Manurangsi

Abstract
We obtain a new protocol for binary counting in the ε-DP_shuffle model with error O(1/ε) and expected communication Õ((log n)/ε) messages per user. Previous protocols incur either an error of O(1/ε^1.5) with O_ε(log n) messages per user (Ghazi et al., ITC 2020) or an error of O(1/ε) with O_ε(n²) messages per user (Cheu and Yan, TPDP 2022). Using the new protocol, we obtained improved ε-DP_shuffle protocols for real summation and histograms.
Cite as

Badih Ghazi, Ravi Kumar, and Pasin Manurangsi. Pure-DP Aggregation in the Shuffle Model: Error-Optimal and Communication-Efficient. In 5th Conference on Information-Theoretic Cryptography (ITC 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 304, pp. 4:1-4:13, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{ghazi_et_al:LIPIcs.ITC.2024.4,
  author =	{Ghazi, Badih and Kumar, Ravi and Manurangsi, Pasin},
  title =	{{Pure-DP Aggregation in the Shuffle Model: Error-Optimal and Communication-Efficient}},
  booktitle =	{5th Conference on Information-Theoretic Cryptography (ITC 2024)},
  pages =	{4:1--4:13},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-333-1},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{304},
  editor =	{Aggarwal, Divesh},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ITC.2024.4},
  URN =		{urn:nbn:de:0030-drops-205127},
  doi =		{10.4230/LIPIcs.ITC.2024.4},
  annote =	{Keywords: Differential Privacy, Shuffle Model, Aggregation, Pure Differential Privacy}
}
Document
DOI: 10.4230/LIPIcs.ITC.2024.5
On the Power of Adaptivity for Function Inversion

Authors: Karthik Gajulapalli, Alexander Golovnev, and Samuel King

Abstract
We study the problem of function inversion with preprocessing where, given a function f : [N] → [N] and a point y in its image, the goal is to find an x such that f(x) = y using at most T oracle queries to f and S bits of preprocessed advice that depend on f. The seminal work of Corrigan-Gibbs and Kogan [TCC 2019] initiated a line of research that shows many exciting connections between the non-adaptive setting of this problem and other areas of theoretical computer science. Specifically, they introduced a very weak class of algorithms (strongly non-adaptive) where the points queried by the oracle depend only on the inversion point y, and are independent of the answers to the previous queries and the S bits of advice. They showed that proving even mild lower bounds on strongly non-adaptive algorithms for function inversion would imply a breakthrough result in circuit complexity. We prove that every strongly non-adaptive algorithm for function inversion (and even for its special case of permutation inversion) must have ST = Ω(N log (N) log (T)). This gives the first improvement to the long-standing lower bound of ST = Ω(N log N) due to Yao [STOC 90]. As a corollary, we conclude the first separation between strongly non-adaptive and adaptive algorithms for permutation inversion, where the adaptive algorithm by Hellman [TOIT 80] achieves the trade-off ST = O(N log N). Additionally, we show equivalence between lower bounds for strongly non-adaptive data structures and the one-way communication complexity of certain partial functions. As an example, we recover our lower bound on function inversion in the communication complexity framework.
Cite as

Karthik Gajulapalli, Alexander Golovnev, and Samuel King. On the Power of Adaptivity for Function Inversion. In 5th Conference on Information-Theoretic Cryptography (ITC 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 304, pp. 5:1-5:10, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{gajulapalli_et_al:LIPIcs.ITC.2024.5,
  author =	{Gajulapalli, Karthik and Golovnev, Alexander and King, Samuel},
  title =	{{On the Power of Adaptivity for Function Inversion}},
  booktitle =	{5th Conference on Information-Theoretic Cryptography (ITC 2024)},
  pages =	{5:1--5:10},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-333-1},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{304},
  editor =	{Aggarwal, Divesh},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ITC.2024.5},
  URN =		{urn:nbn:de:0030-drops-205137},
  doi =		{10.4230/LIPIcs.ITC.2024.5},
  annote =	{Keywords: Function Inversion, Non-Adaptive lower bounds, Communication Complexity}
}
Document
DOI: 10.4230/LIPIcs.ITC.2024.6
Information-Theoretic Single-Server PIR in the Shuffle Model

Authors: Yuval Ishai, Mahimna Kelkar, Daniel Lee, and Yiping Ma

Abstract
We revisit the problem of private information retrieval (PIR) in the shuffle model, where queries can be made anonymously by multiple clients. We present the first single-server PIR protocol in this model that has sublinear per-client communication and information-theoretic security. Moreover, following one-time preprocessing on the server side, our protocol only requires sublinear per-client computation. Concretely, for every γ > 0, the protocol has O(n^{γ}) communication and computation costs per (stateless) client, with 1/poly(n) statistical security, assuming that a size-n database is simultaneously accessed by poly(n) clients. This should be contrasted with the recent breakthrough result of Lin, Mook, and Wichs (STOC 2023) on doubly efficient PIR in the standard model, which is (inherently) limited to computational security.
Cite as

Yuval Ishai, Mahimna Kelkar, Daniel Lee, and Yiping Ma. Information-Theoretic Single-Server PIR in the Shuffle Model. In 5th Conference on Information-Theoretic Cryptography (ITC 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 304, pp. 6:1-6:23, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{ishai_et_al:LIPIcs.ITC.2024.6,
  author =	{Ishai, Yuval and Kelkar, Mahimna and Lee, Daniel and Ma, Yiping},
  title =	{{Information-Theoretic Single-Server PIR in the Shuffle Model}},
  booktitle =	{5th Conference on Information-Theoretic Cryptography (ITC 2024)},
  pages =	{6:1--6:23},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-333-1},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{304},
  editor =	{Aggarwal, Divesh},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ITC.2024.6},
  URN =		{urn:nbn:de:0030-drops-205142},
  doi =		{10.4230/LIPIcs.ITC.2024.6},
  annote =	{Keywords: Private information retrieval, Shuffle model}
}
Document
DOI: 10.4230/LIPIcs.ITC.2024.7
Improved Trade-Offs Between Amortization and Download Bandwidth for Linear HSS

Authors: Keller Blackwell and Mary Wootters

Abstract
A Homomorphic Secret Sharing (HSS) scheme is a secret-sharing scheme that shares a secret x among s servers, and additionally allows an output client to reconstruct some function f(x) using information that can be locally computed by each server. A key parameter in HSS schemes is download rate, which quantifies how much information the output client needs to download from the servers. Often, download rate is improved by amortizing over 𝓁 instances of the problem, making 𝓁 also a key parameter of interest. Recent work [Fosli et al., 2022] established a limit on the download rate of linear HSS schemes for computing low-degree polynomials and constructed schemes that achieve this optimal download rate; their schemes required amortization over 𝓁 = Ω(s log(s)) instances of the problem. Subsequent work [Blackwell and Wootters, 2023] completely characterized linear HSS schemes that achieve optimal download rate in terms of a coding-theoretic notion termed optimal labelweight codes. A consequence of this characterization was that 𝓁 = Ω(s log(s)) is in fact necessary to achieve optimal download rate. In this paper, we characterize all linear HSS schemes, showing that schemes of any download rate are equivalent to a generalization of optimal labelweight codes. This equivalence is constructive and provides a way to obtain an explicit linear HSS scheme from any linear code. Using this characterization, we present explicit linear HSS schemes with slightly sub-optimal rate but with much improved amortization 𝓁 = O(s). Our constructions are based on algebraic geometry codes (specifically Hermitian codes and Goppa codes).
Cite as

Keller Blackwell and Mary Wootters. Improved Trade-Offs Between Amortization and Download Bandwidth for Linear HSS. In 5th Conference on Information-Theoretic Cryptography (ITC 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 304, pp. 7:1-7:21, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{blackwell_et_al:LIPIcs.ITC.2024.7,
  author =	{Blackwell, Keller and Wootters, Mary},
  title =	{{Improved Trade-Offs Between Amortization and Download Bandwidth for Linear HSS}},
  booktitle =	{5th Conference on Information-Theoretic Cryptography (ITC 2024)},
  pages =	{7:1--7:21},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-333-1},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{304},
  editor =	{Aggarwal, Divesh},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ITC.2024.7},
  URN =		{urn:nbn:de:0030-drops-205156},
  doi =		{10.4230/LIPIcs.ITC.2024.7},
  annote =	{Keywords: Error Correcting Codes, Homomorphic Secret Sharing}
}
Document
DOI: 10.4230/LIPIcs.ITC.2024.8
Breaking RSA Generically Is Equivalent to Factoring, with Preprocessing

Authors: Dana Dachman-Soled, Julian Loss, and Adam O'Neill

Abstract
We investigate the relationship between the classical RSA and factoring problems when preprocessing is considered. In such a model, adversaries can use an unbounded amount of precomputation to produce an "advice" string to then use during the online phase, when a problem instance becomes known. Previous work (e.g., [Bernstein, Lange ASIACRYPT '13]) has shown that preprocessing attacks significantly improve the runtime of the best-known factoring algorithms. Due to these improvements, we ask whether the relationship between factoring and RSA fundamentally changes when preprocessing is allowed. Specifically, we investigate whether there is a superpolynomial gap between the runtime of the best attack on RSA with preprocessing and on factoring with preprocessing. Our main result rules this out with respect to algorithms that perform generic computation on the RSA instance x^e od N yet arbitrary computation on the modulus N, namely a careful adaptation of the well-known generic ring model of Aggarwal and Maurer (Eurocrypt 2009) to the preprocessing setting. In particular, in this setting we show the existence of a factoring algorithm with polynomially related parameters, for any setting of RSA parameters. Our main technical contribution is a set of new information-theoretic techniques that allow us to handle or eliminate cases in which the Aggarwal and Maurer result does not yield a factoring algorithm in the standard model with parameters that are polynomially related to those of the RSA algorithm. These techniques include two novel compression arguments, and a variant of the Fiat-Naor/Hellman tables construction that is tailored to the factoring setting.
Cite as

Dana Dachman-Soled, Julian Loss, and Adam O'Neill. Breaking RSA Generically Is Equivalent to Factoring, with Preprocessing. In 5th Conference on Information-Theoretic Cryptography (ITC 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 304, pp. 8:1-8:24, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{dachmansoled_et_al:LIPIcs.ITC.2024.8,
  author =	{Dachman-Soled, Dana and Loss, Julian and O'Neill, Adam},
  title =	{{Breaking RSA Generically Is Equivalent to Factoring, with Preprocessing}},
  booktitle =	{5th Conference on Information-Theoretic Cryptography (ITC 2024)},
  pages =	{8:1--8:24},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-333-1},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{304},
  editor =	{Aggarwal, Divesh},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ITC.2024.8},
  URN =		{urn:nbn:de:0030-drops-205163},
  doi =		{10.4230/LIPIcs.ITC.2024.8},
  annote =	{Keywords: RSA, factoring, generic ring model, preprocessing}
}
Document
DOI: 10.4230/LIPIcs.ITC.2024.9
Time-Space Tradeoffs for Finding Multi-Collisions in Merkle-Damgård Hash Functions

Authors: Akshima

Abstract
We analyze the multi-collision resistance of Merkle-Damgård hash function construction in the auxiliary input random oracle model. Finding multi-collisions or m-way collisions, for some parameter m, in a hash function consists of m distinct input that have the same output under the hash function. This is a natural generalization of the collision finding problem in hash functions, which is basically finding 2-way collisions. Hardness of finding collisions, or collision resistance, is an important security assumption in cryptography. While the time-space trade-offs for collision resistance of hash functions has received considerable attention, this is the first work that studies time-space trade-offs for the multi-collision resistance property of hash functions based on the popular and widely used Merkle-Damgård (MD) constructions. In this work, we study how the advantage of finding m-way collisions depends on the parameter m. We believe understanding whether multi-collision resistance is a strictly easier property than collision resistance is a fundamental problem and our work facilitates this for adversaries with auxiliary information against MD based hash functions. Furthermore, in this work we study how the advantage varies with the bound on length of the m colliding inputs. Prior works [Akshima et al., 2020; Ashrujit Ghoshal and Ilan Komargodski, 2022; Akshima et al., 2022] have shown that finding "longer" collisions with auxiliary input in MD based hash functions becomes easier. More precisely, the advantage of finding collisions linearly depends on the bound on the length of colliding inputs. In this work, we show similar dependence for m-way collision finding, for any m ≥ 2. We show a simple attack for finding 1-block m-way collisions which achieves an advantage of Ω̃(S/mN). For 2 ≤ B < log m, we give the best known attack for finding B-blocks m-way collision which achieves an advantage of Ω̃(ST/m^{1/(B-1)}N) when m^{1/(B-1)}-way collisions exist on every salt. For B > log m, our attack achieves an advantage of Ω̃(STB/N) which is optimal when SB ≥ T and ST² ≤ N. The main results of this work is showing that our attacks are optimal for B = 1 and B = 2. This implies that in the auxiliary-input random oracle model, the advantage decreases by a multiplicative factor of m for finding 1-block and 2-block m-way collisions (compared to collision finding) in Merkle-Damgård based hash functions.
Cite as

Akshima. Time-Space Tradeoffs for Finding Multi-Collisions in Merkle-Damgård Hash Functions. In 5th Conference on Information-Theoretic Cryptography (ITC 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 304, pp. 9:1-9:22, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{akshima:LIPIcs.ITC.2024.9,
  author =	{Akshima},
  title =	{{Time-Space Tradeoffs for Finding Multi-Collisions in Merkle-Damg\r{a}rd Hash Functions}},
  booktitle =	{5th Conference on Information-Theoretic Cryptography (ITC 2024)},
  pages =	{9:1--9:22},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-333-1},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{304},
  editor =	{Aggarwal, Divesh},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ITC.2024.9},
  URN =		{urn:nbn:de:0030-drops-205171},
  doi =		{10.4230/LIPIcs.ITC.2024.9},
  annote =	{Keywords: Collision, hash functions, multi-collisions, Merkle-Damg\r{a}rd, pre-computation, auxiliary input}
}
Document
DOI: 10.4230/LIPIcs.ITC.2024.10
Secure Multiparty Computation of Symmetric Functions with Polylogarithmic Bottleneck Complexity and Correlated Randomness

Authors: Reo Eriguchi

Abstract
Bottleneck complexity is an efficiency measure of secure multiparty computation (MPC) protocols introduced to achieve load-balancing in large-scale networks, which is defined as the maximum communication complexity required by any one player within the protocol execution. Towards the goal of achieving low bottleneck complexity, prior works proposed MPC protocols for computing symmetric functions in the correlated randomness model, where players are given input-independent correlated randomness in advance. However, the previous protocols with polylogarithmic bottleneck complexity in the number n of players require a large amount of correlated randomness that is linear in n, which limits the per-party efficiency as receiving and storing correlated randomness are the bottleneck for efficiency. In this work, we present for the first time MPC protocols for symmetric functions such that bottleneck complexity and the amount of correlated randomness are both polylogarithmic in n, assuming semi-honest adversaries colluding with at most n-o(n) players. Furthermore, one of our protocols is even computationally efficient in that each player performs only polylog(n) arithmetic operations while the computational complexity of the previous protocols is O(n). Technically, our efficiency improvements come from novel protocols based on ramp secret sharing to realize basic functionalities with low bottleneck complexity, which we believe may be of interest beyond their applications to secure computation of symmetric functions.
Cite as

Reo Eriguchi. Secure Multiparty Computation of Symmetric Functions with Polylogarithmic Bottleneck Complexity and Correlated Randomness. In 5th Conference on Information-Theoretic Cryptography (ITC 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 304, pp. 10:1-10:22, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{eriguchi:LIPIcs.ITC.2024.10,
  author =	{Eriguchi, Reo},
  title =	{{Secure Multiparty Computation of Symmetric Functions with Polylogarithmic Bottleneck Complexity and Correlated Randomness}},
  booktitle =	{5th Conference on Information-Theoretic Cryptography (ITC 2024)},
  pages =	{10:1--10:22},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-333-1},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{304},
  editor =	{Aggarwal, Divesh},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ITC.2024.10},
  URN =		{urn:nbn:de:0030-drops-205182},
  doi =		{10.4230/LIPIcs.ITC.2024.10},
  annote =	{Keywords: Secure multiparty computation, Bottleneck complexity, Secret sharing}
}
Document
DOI: 10.4230/LIPIcs.ITC.2024.11
Fast Secure Computations on Shared Polynomials and Applications to Private Set Operations

Authors: Pascal Giorgi, Fabien Laguillaumie, Lucas Ottow, and Damien Vergnaud

Abstract
Secure multi-party computation aims to allow a set of players to compute a given function on their secret inputs without revealing any other information than the result of the computation. In this work, we focus on the design of secure multi-party protocols for shared polynomial operations. We consider the classical model where the adversary is honest-but-curious, and where the coefficients (or any secret values) are either encrypted using an additively homomorphic encryption scheme or shared using a threshold linear secret-sharing scheme. Our protocols terminate after a constant number of rounds and minimize the number of secure multiplications. In their seminal article at PKC 2006, Mohassel and Franklin proposed constant-rounds protocols for the main operations on (shared) polynomials. In this work, we improve the fan-in multiplication of nonzero polynomials, the multi-point polynomial evaluation and the polynomial interpolation (on secret points) to reach a quasi-linear complexity (instead of quadratic in Mohassel and Franklin’s work) in the degree of shared input/output polynomials. Computing with shared polynomials is a core component of several multi-party protocols for privacy-preserving operations on private sets, like the private disjointness test or the private set intersection. Using our new protocols, we are able to improve the complexity of such protocols and to design the first variants which always return a correct result.
Cite as

Pascal Giorgi, Fabien Laguillaumie, Lucas Ottow, and Damien Vergnaud. Fast Secure Computations on Shared Polynomials and Applications to Private Set Operations. In 5th Conference on Information-Theoretic Cryptography (ITC 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 304, pp. 11:1-11:24, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{giorgi_et_al:LIPIcs.ITC.2024.11,
  author =	{Giorgi, Pascal and Laguillaumie, Fabien and Ottow, Lucas and Vergnaud, Damien},
  title =	{{Fast Secure Computations on Shared Polynomials and Applications to Private Set Operations}},
  booktitle =	{5th Conference on Information-Theoretic Cryptography (ITC 2024)},
  pages =	{11:1--11:24},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-333-1},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{304},
  editor =	{Aggarwal, Divesh},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ITC.2024.11},
  URN =		{urn:nbn:de:0030-drops-205194},
  doi =		{10.4230/LIPIcs.ITC.2024.11},
  annote =	{Keywords: Multi-party computation, polynomial operations, privacy-preserving set operations}
}

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