4 Search Results for "Venturi, Daniele"

Document
DOI: 10.4230/LIPIcs.ITCS.2026.62
Improved Rate for Non-Malleable Codes and Time-Lock Puzzles

Authors: Cody Freitag, Ilan Komargodski, Manu Kondapaneni, and Jad Silbak

Published in: LIPIcs, Volume 362, 17th Innovations in Theoretical Computer Science Conference (ITCS 2026)

Abstract
Non-malleable codes allow a sender to transmit a message to a receiver, while providing a "best-possible" integrity guarantee to ensure that no attacker - who cannot already decode the message - can meaningfully tamper the message in transit. If tampered, the received message should either be invalid or unrelated to the original message. Non-malleable time-lock puzzles (TLPs) are a special case of non-malleable codes for bounded polynomial-depth tampering with very efficient encoding. In this work, we give generic techniques for constructing non-malleable codes and non-malleable TLPs with improved rate, which captures the ratio of a message’s length to its encoding length. A key contribution of our work is identifying a security notion for non-malleability, which we term "CCA-hiding", sufficient for our compilers. CCA-hiding is a relaxation of CCA-security for encryption or commitments to the fine-grained setting of codes, and requires that the encoded message remains hidden, even given a decoding oracle for any other codeword. Intriguingly, CCA-hiding does not imply non-malleability in the fine-grained setting, as is the case for encryption and commitments. Using our new techniques, we give the following constructions: - Rate-1 CCA-hiding TLPs in the plain model. - Rate-1 non-malleable codes for bounded polynomial-depth tampering in the auxiliary-input random oracle model (AI-ROM). - Rate-(1/2) non-malleable TLPs in the AI-ROM.
Cite as

Cody Freitag, Ilan Komargodski, Manu Kondapaneni, and Jad Silbak. Improved Rate for Non-Malleable Codes and Time-Lock Puzzles. In 17th Innovations in Theoretical Computer Science Conference (ITCS 2026). Leibniz International Proceedings in Informatics (LIPIcs), Volume 362, pp. 62:1-62:24, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2026)

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@InProceedings{freitag_et_al:LIPIcs.ITCS.2026.62,
  author =	{Freitag, Cody and Komargodski, Ilan and Kondapaneni, Manu and Silbak, Jad},
  title =	{{Improved Rate for Non-Malleable Codes and Time-Lock Puzzles}},
  booktitle =	{17th Innovations in Theoretical Computer Science Conference (ITCS 2026)},
  pages =	{62:1--62:24},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-410-9},
  ISSN =	{1868-8969},
  year =	{2026},
  volume =	{362},
  editor =	{Saraf, Shubhangi},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ITCS.2026.62},
  URN =		{urn:nbn:de:0030-drops-253490},
  doi =		{10.4230/LIPIcs.ITCS.2026.62},
  annote =	{Keywords: Non-malleable codes, Time-lock puzzles}
}
Document
DOI: 10.4230/LIPIcs.DISC.2025.4
pod: An Optimal-Latency, Censorship-Free, and Accountable Generalized Consensus Layer

Authors: Orestis Alpos, Bernardo David, Jakov Mitrovski, Odysseas Sofikitis, and Dionysis Zindros

Published in: LIPIcs, Volume 356, 39th International Symposium on Distributed Computing (DISC 2025)

Abstract
This work addresses the inherent issues of high latency in blockchains and low scalability in traditional consensus protocols. We present pod, a novel notion of consensus whose first priority is to achieve the physically-optimal latency of 2δ, or one round-trip, i.e., requiring only one network trip (duration δ) for writing a transaction and one for reading it. To accomplish this, we first eliminate inter-replica communication. Instead, clients send transactions directly to all replicas, which independently process transactions and append them to local logs. Replicas assign a timestamp and a sequence number to each transaction in their logs, allowing clients to extract valuable metadata about the transactions and the system state. Later on, clients retrieve these logs and extract transactions (and associated metadata) from them. Necessarily, this construction achieves weaker properties than a total-order broadcast protocol, due to existing lower bounds. Our work models the primitive of pod and defines its security properties. We then show pod-core, a protocol that satisfies properties such as transaction confirmation within 2δ, censorship resistance against Byzantine replicas, and accountability for safety violations. We show that single-shot auctions can be realized using the pod notion and observe that it is also sufficient for other popular applications.
Cite as

Orestis Alpos, Bernardo David, Jakov Mitrovski, Odysseas Sofikitis, and Dionysis Zindros. pod: An Optimal-Latency, Censorship-Free, and Accountable Generalized Consensus Layer. In 39th International Symposium on Distributed Computing (DISC 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 356, pp. 4:1-4:24, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{alpos_et_al:LIPIcs.DISC.2025.4,
  author =	{Alpos, Orestis and David, Bernardo and Mitrovski, Jakov and Sofikitis, Odysseas and Zindros, Dionysis},
  title =	{{pod: An Optimal-Latency, Censorship-Free, and Accountable Generalized Consensus Layer}},
  booktitle =	{39th International Symposium on Distributed Computing (DISC 2025)},
  pages =	{4:1--4:24},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-402-4},
  ISSN =	{1868-8969},
  year =	{2025},
  volume =	{356},
  editor =	{Kowalski, Dariusz R.},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.DISC.2025.4},
  URN =		{urn:nbn:de:0030-drops-248219},
  doi =		{10.4230/LIPIcs.DISC.2025.4},
  annote =	{Keywords: consensus, censorship resistance, accountability, auctions}
}
Document
DOI: 10.4230/LIPIcs.ITC.2022.5
From Privacy-Only to Simulatable OT: Black-Box, Round-Optimal, Information-Theoretic

Authors: Varun Madathil, Chris Orsini, Alessandra Scafuro, and Daniele Venturi

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

Abstract
We present an information-theoretic transformation from any 2-round OT protocol with only game-based security in the presence of malicious adversaries into a 4-round (which is known to be optimal) OT protocol with simulation-based security in the presence of malicious adversaries. Our transform is the first satisfying all of the following properties at the same time: - It is in the plain model, without requiring any setup assumption. - It only makes black-box usage of the underlying OT protocol. - It is information-theoretic, as it does not require any further cryptographic assumption (besides the existence of the underlying OT protocol). Additionally, our transform yields a cubic improvement in communication complexity over the best previously known transformation.
Cite as

Varun Madathil, Chris Orsini, Alessandra Scafuro, and Daniele Venturi. From Privacy-Only to Simulatable OT: Black-Box, Round-Optimal, Information-Theoretic. In 3rd Conference on Information-Theoretic Cryptography (ITC 2022). Leibniz International Proceedings in Informatics (LIPIcs), Volume 230, pp. 5:1-5:20, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)

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@InProceedings{madathil_et_al:LIPIcs.ITC.2022.5,
  author =	{Madathil, Varun and Orsini, Chris and Scafuro, Alessandra and Venturi, Daniele},
  title =	{{From Privacy-Only to Simulatable OT: Black-Box, Round-Optimal, Information-Theoretic}},
  booktitle =	{3rd Conference on Information-Theoretic Cryptography (ITC 2022)},
  pages =	{5:1--5:20},
  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.dagstuhl.de/entities/document/10.4230/LIPIcs.ITC.2022.5},
  URN =		{urn:nbn:de:0030-drops-164836},
  doi =		{10.4230/LIPIcs.ITC.2022.5},
  annote =	{Keywords: Oblivious Transfer, Black-Box compiler, Malicious Security, Plain Model}
}
Document
Track A: Algorithms, Complexity and Games
DOI: 10.4230/LIPIcs.ICALP.2020.55
Cryptographic Reverse Firewalls for Interactive Proof Systems

Authors: Chaya Ganesh, Bernardo Magri, and Daniele Venturi

Published in: LIPIcs, Volume 168, 47th International Colloquium on Automata, Languages, and Programming (ICALP 2020)

Abstract
We study interactive proof systems (IPSes) in a strong adversarial setting where the machines of honest parties might be corrupted and under control of the adversary. Our aim is to answer the following, seemingly paradoxical, questions: - Can Peggy convince Vic of the veracity of an NP statement, without leaking any information about the witness even in case Vic is malicious and Peggy does not trust her computer? - Can we avoid that Peggy fools Vic into accepting false statements, even if Peggy is malicious and Vic does not trust her computer? At EUROCRYPT 2015, Mironov and Stephens-Davidowitz introduced cryptographic reverse firewalls (RFs) as an attractive approach to tackling such questions. Intuitively, a RF for Peggy/Vic is an external party that sits between Peggy/Vic and the outside world and whose scope is to sanitize Peggy’s/Vic’s incoming and outgoing messages in the face of subversion of her/his computer, e.g. in order to destroy subliminal channels. In this paper, we put forward several natural security properties for RFs in the concrete setting of IPSes. As our main contribution, we construct efficient RFs for different IPSes derived from a large class of Sigma protocols that we call malleable. A nice feature of our design is that it is completely transparent, in the sense that our RFs can be directly applied to already deployed IPSes, without the need to re-implement them.
Cite as

Chaya Ganesh, Bernardo Magri, and Daniele Venturi. Cryptographic Reverse Firewalls for Interactive Proof Systems. In 47th International Colloquium on Automata, Languages, and Programming (ICALP 2020). Leibniz International Proceedings in Informatics (LIPIcs), Volume 168, pp. 55:1-55:16, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)

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@InProceedings{ganesh_et_al:LIPIcs.ICALP.2020.55,
  author =	{Ganesh, Chaya and Magri, Bernardo and Venturi, Daniele},
  title =	{{Cryptographic Reverse Firewalls for Interactive Proof Systems}},
  booktitle =	{47th International Colloquium on Automata, Languages, and Programming (ICALP 2020)},
  pages =	{55:1--55:16},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-138-2},
  ISSN =	{1868-8969},
  year =	{2020},
  volume =	{168},
  editor =	{Czumaj, Artur and Dawar, Anuj and Merelli, Emanuela},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ICALP.2020.55},
  URN =		{urn:nbn:de:0030-drops-124621},
  doi =		{10.4230/LIPIcs.ICALP.2020.55},
  annote =	{Keywords: Subversion, Algorithm substitution attacks, Cryptographic reverse firewalls, Interactive proofs, Zero knowledge}
}
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