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4,228 results · page 140 of 177
Sébastien Canard, Adel Hamdi, Fabien Laguillaumie
No abstract is available for this record.
Aditya Damodaran, Alfredo Rial
No abstract is available for this record.
Jayamine Alupotha, Xavier Boyen, Ernest Foo
No abstract is available for this record.
Kai Hendrik Wöhnert, Sven-Jannik Wöhnert, Tobias Thiel, Rüdiger Weißbach · 5 authors
Production systems equipped with industrial internet-of-things devices are on the rise allowing smart manufacturing within the trend of industry 4.0 by implementing decentralized decision making. The interconnected devices allow for high transparency in systems by tracking environmental data and actions performed by the actors of the systems. However, they are an easy target for attackers to tamper the authenticity, accountability, and integrity of systems. Therefore, trusted data within systems is required. The trust bases on well-behavior over a period of time of a dedicated entity. Therefore, entities have to be identified to track their behavior. Here, a system of verifiable distributed identities is presented and verified by a simulation. Using a newly introduced zero-knowledge-proof with only two packages exchanged a secure replacement of parts of a product such as a production machine can be achieved without relying on a central authority during the product’s utilization phase.
Thomas H. Haines, Dirk Pattinson, Mukesh Tiwari
No abstract is available for this record.
Michele Ciampi, Roberto Parisella, Daniele Venturi
We study adaptive security of delayed-input Sigma protocols and non-interactive zero-knowledge (NIZK) proof systems in the common reference string (CRS) model. Our contributions are threefold: We exhibit a generic compiler taking any delayed-input Sigma protocol and returning a delayed-input Sigma protocol satisfying adaptive-input special honest-verifier zero knowledge (SHVZK). In case the initial Sigma protocol also satisfies adaptive-input special soundness, our compiler preserves this property. We revisit the recent paradigm by Canetti et al. (STOC 2019) for obtaining NIZK proof systems in the CRS model via the Fiat-Shamir transform applied to so-called trapdoor Sigma protocols, in the context of adaptive security. In particular, assuming correlation-intractable hash functions for all sparse relations, we prove that Fiat-Shamir NIZKs satisfy either: (i) Adaptive soundness (and non-adaptive zero knowledge), so long as the challenge is obtained by hashing both the prover’s first round and the instance being proven; (ii) Adaptive zero knowledge (and non-adaptive soundness), so long as the challenge is obtained by hashing only the prover’s first round, and further assuming that the initial trapdoor Sigma protocol satisfies adaptive-input SHVZK. We exhibit a generic compiler taking any Sigma protocol and returning a trapdoor Sigma protocol. Unfortunately, this transform does not preserve the delayed-input property of the initial Sigma protocol (if any). To complement this result, we also give yet another compiler taking any delayed-input trapdoor Sigma protocol and returning a delayed-input trapdoor Sigma protocol with adaptive-input SHVZK.
Benoît Libert, Khoa Nguyen, Alain Passelègue, Radu Ţiţiu
No abstract is available for this record.
Swarnadeep Saha, Sayan Ghosh, Shashank Srivastava, Mohit Bansal
shows that transformers can act as "soft theorem provers" by answering questions over explicitly provided knowledge in natural language. In our work, we take a step closer to emulating formal theorem provers, by proposing PROVER, an interpretable transformer-based model that jointly answers binary questions over rule-bases and generates the corresponding proofs. Our model learns to predict nodes and edges corresponding to proof graphs in an efficient constrained training paradigm. During inference, a valid proof, satisfying a set of global constraints is generated. We conduct experiments on synthetic, hand-authored, and human-paraphrased rule-bases to show promising results for QA and proof generation, with strong generalization performance. First, PROVER generates proofs with an accuracy of 87%, while retaining or improving performance on the QA task, compared to RuleTakers (up to 6% improvement on zero-shot evaluation). Second, when trained on questions requiring lower depths of reasoning, it generalizes significantly better to higher depths (up to 15% improvement). Third, PROVER obtains near perfect QA accuracy of 98% using only 40% of the training data. However, generating proofs for questions requiring higher depths of reasoning becomes challenging, and the accuracy drops to 65% for "depth 5", indicating significant scope for future work.
Sergey Zapechnikov
The article deals with the problems of cryptographic protection of data processing algorithms and techniques. They are novel techniques allowing to process private information without disclosing it to persons engaged in processing. One of the main applications of such security tools is the creation of personalized information services, which opens up new opportunities for business and reduces the risks of unauthorized access to personal data. We review important building blocks for cryptographic protection of data processing, such as zero-knowledge proofs, secure multi-party computations, and homomorphic encryption. Often, personalized information services are based on data mining and machine learning, so privacy-preserved machine learning is a very important building block for them. We analyze the concept of differential privacy which serves as the basis for privacy-preserving machine learning and some other cryptographic schemes. At the end of the paper, we forecast the perspectives of encrypted data processing.
Shubham Sahai, Pramod Subramanyan, Rohit Sinha
Many important cryptographic primitives offer probabilistic guarantees of security that can be specified as quantitative hyperproperties; these are specifications that stipulate the existence of a certain number of traces in the system satisfying certain constraints. Verification of such hyperproperties is extremely challenging because they involve simultaneous reasoning about an unbounded number of different traces. In this paper, we introduce a technique for verification of quantitative hyperproperties based on the notion of trace enumeration relations. These relations allow us to reduce the problem of trace-counting into one of model-counting of formulas in first-order logic. We also introduce a set of inference rules for machine-checked reasoning about the number of satisfying solutions to first-order formulas (aka model counting). Putting these two components together enables semi-automated verification of quantitative hyperproperties on infinite state systems. We use our methodology to prove confidentiality of access patterns in Path ORAMs of unbounded size, soundness of a simple interactive zero-knowledge proof protocol as well as other applications of quantitative hyperproperties studied in past work.
Ward Beullens, Cyprien Delpech de Saint Guilhem
No abstract is available for this record.
Chloé Hébant, Duong Hieu Phan, David Pointcheval
No abstract is available for this record.
Ying Miao, Qiong Huang, Meiyan Xiao, Hongbo Li
Cloud storage systems provide a flexible, convenient and friendly way for users to outsource data. However, users lose control of their data once outsourcing them to the cloud. Public auditing was introduced to ensure data integrity, in which a third-party auditor (TPA) is delegated to execute auditing tasks. In general, TPA generates and sends challenge information to the cloud server (CS), which proves data possession accordingly. However, the TPA may not perform public auditing protocol honestly or may even collude with CS to deceive users. Some existing public auditing schemes utilize blockchain to resist against the malicious TPA. However, the CS may guess the challenge messages and there is a risk that users' information may be leaked to the TPA during the process of auditing. In this paper, we propose a decentralized and privacy-preserving public auditing scheme based on blockchain (DBPA), in which a blockchain is utilized as an unpredictable source for the generation of (random) challenge information, and the auditor is required to record the audit process onto the blockchain. Due to the characteristics of blockchain, users can check the audit results publicly. Moreover, zero-knowledge proof is used in DBPA to protect user's privacy during the audit process so that the response information returned by the CS does not leak information about user's data. Security analysis and performance evaluation show that DBPA is secure and efficient.
Zongyang Zhang, Weihan Li, Haitao Liu, Jianwei Liu
With the continuous development and popularity of blockchain technology, anonymity of cryptocurrency has attracted wide attention. Zcash is an altcoin of Bitcoin aiming to protect blockchain anonymity. Its anonymity is highly guaranteed by zero-knowledge proofs. However, it is still practicable to decrease Zcash's anonymity. In this paper, we provide a refined empirical analysis of Zcash anonymity. We improve current address clustering methods and increase the clustering rate by 9%. We also analyze the whole process of distributing mining reward and identify 87.5% addresses and 25.7% transactions. Besides, we simplify Zcash transaction network and then pick out nodes (edges) which play important roles in network connectivity. We show that these nodes are mostly mining pools. In particular, users participating in shieldedpool are mostly founders, miners and mining pools, although shieldedpool itself is designed for protecting anonymity of users with high privacy requirements. Our results, to an extent, are opposite to the original intention of Zcash.
Rui Morais, Paul Crocker, Simão Melo de Sousa
We present a modification to RingCT protocol with stealth addresses that makes it compatible with Delegated Proof of Stake based consensus mechanisms called Delegated RingCT. Our scheme has two building blocks: a customised version of an Integrated Signature and Encryption scheme composed of a public key encryption scheme and two signature schemes (a digital signature and a linkable ring signature); and non-interactive zero knowledge proofs. We give a description of the scheme, security proofs and a prototype implementation whose benchmarking is discussed. Although Delegated RingCT doesn't have the same degree of anonymity as other RingCT constructions, we argue that the benefits that the compatibility with DPoS consensus mechanisms brings constitutes a reasonable trade-off for being able to develop an anonymous decentralised cryptocurrency that is faster and more scalable than existing ones.
Daiki Miyahara, Léo Robert, Pascal Lafourcade, So Takeshige · 8 authors
Takuzu and Juosan are logical Nikoli games in the spirit of Sudoku. In Takuzu, a grid must be filled with 0’s and 1’s under specific constraints. In Juosan, the grid must be filled with vertical and horizontal dashes with specific constraints. We give physical algorithms using cards to realize zero-knowledge proofs for those games. The goal is to allow a player to show that he/she has the solution without revealing it. Previous work on Takuzu showed a protocol with multiple instances needed. We propose two improvements: only one instance needed and a soundness proof. We also propose a similar proof for Juosan game.
Florian Tramèr, Dan Boneh, Kenneth G. Paterson
Privacy-focused crypto-currencies, such as Zcash or Monero, aim to provide strong cryptographic guarantees for transaction confidentiality and unlinkability.In this paper, we describe side-channel attacks that let remote adversaries bypass these protections.We present a general class of timing side-channel and traffic-analysis attacks on receiver privacy.These attacks enable an active remote adversary to identify the (secret) payee of any transaction in Zcash or Monero.The attacks violate the privacy goals of these crypto-currencies by exploiting side-channel information leaked by the implementation of different system components.Specifically, we show that a remote party can link all transactions that send funds to a user, by measuring the response time of that user's P2P node to certain requests.The timing differences are large enough that the attacks can be mounted remotely over a WAN.We responsibly disclosed the issues to the affected projects, and they have patched the vulnerabilities.We further study the impact of timing side-channels on the zero-knowledge proof systems used in these cryptocurrencies.We observe that in Zcash's implementation, the time to generate a zero-knowledge proof depends on secret transaction data, and in particular on the amount of transacted funds.Hence, an adversary capable of measuring proof generation time could break transaction confidentiality, despite the proof system's zero-knowledge property.Our attacks highlight the dangers of side-channel leakage in anonymous crypto-currencies, and the need to systematically protect them against such attacks.
Aly Ibrahim
No-signalling (NOSIG) correlations, that are stronger than those allowed by quantum entanglement yet do not violate relativistic causality, are a valuable resource for understanding information processing systems. Such correlations can be achieved between non-communicating players in games when the players use what is called non-local strategies, and can give the players better odds at winning in these games. We propose definitions for non-local strategies in relativistic multi-player non-local games. We prove a conjecture by Crépeau stating that any non-local strategy that can be simultaneously produced by any pi-signalling strategy in a multi-player non-local game, has to be a NOSIG strategy. Pi-signalling strategies are achieved when 1-way signalling is allowed between players arranged on a line defined by some permutation. This result gives us a better understanding of how NOSIG strategies fit with the other non-local strategies, and can help in constructing novel NOSIG multi-player strategies and help prove they produce NOSIG correlations. Finally, we extend the definition of zero-knowledge proof systems to the relativistic multi-prover, multi-verifier setting, and propose definitions for what it means for a non-local strategy to have polynomial time complexity
Carsten Baum, Daniele Cozzo, Nigel P. Smart
The HighGear protocol (Eurocrypt 2018) is the fastest currently known approach to preprocessing for the SPDZ Multi-Party Computation scheme. Its backbone is formed by an Ideal Lattice-based Somewhat Homomorphic Encryption Scheme and accompanying Zero-Knowledge proofs. Unfortunately, due to certain characteristics of HighGear such current implementations limit the security parameters in a number of places. This is mainly due to memory and bandwidth consumption constraints. In this work we present a new approach to the ZKPoKs for the SPDZ Multi-Party Computation scheme. We rigorously formalize the original approach of HighGear and show how to improve upon it using a different proof strategy. This allows us to increase the security of the underlying protocols, whilst simultaneously also increasing the performance in terms of memory and bandwidth consumption as well as overall throughput of the SPDZ offline phase.
Antti Tani
Bitcoinin julkaisu merkitsi samalla lohkoketjusovellusten syntymää. Johtuen muun muassa julkisen todennettavuuden tarpeesta, lohkoketjussa säilytettävä tieto on tyypillisesti läpinäkyvää, joka voi olla ongelmallista yksityisyyden kannalta. Yksityisyyden parantamiseksi on kehitetty menetelmiä, jotka hämärtävät lohkoketjun tietojen läpinäkyvyyttä säilyttäen niiden eheyden ja todennettavuuden. Lupaava kryptografinen menetelmä tähän tarkoitukseen on nollatietotodistus, joka mahdollistaa väitteen todistamisen siten, että ainoa todistuksessa paljastuva tieto on väitteen totuusarvo. \n \nNollatietotodistuksiin perehtyminen aloitetaan niiden teoreettisesta perustasta. Lohkoketjujen kannalta tärkeitä vaatimuksia nollatietotodistuksille ovat ei-interaktiivisuus ja ytimekkyys, ja nämä ehdot täyttäviä todistusrakenteita kutsutaan yleisesti nimellä zk-SNARK. Fiat-Shamir muunnos on käyttökelpoinen menetelmä ei-interaktiivisen nollatietotodistuksen muodostamiseen tapauksissa, joissa ytimekkyys ei ole tärkeää. Nollatietotodistusten käyttöä tutkitaan erityisesti yksityisyyden ja käyttökelpoisuuden kannalta kolmessa lohkoketjusovelluksessa, jotka ovat Zcash, Ethereum ja Monero.
Suthee Ruangwises, Toshiya Itoh
Numberlink is a logic puzzle for which the player has to connect all pairs of cells with the same numbers by non-crossing paths in a rectangular grid. In this paper, we propose a physical protocol of zero-knowledge proof for Numberlink using a deck of cards, which allows a player to physically show that he/she knows a solution without revealing it. In particular, we develop a physical protocol to count the number of elements in a list that are equal to a given secret value without revealing that value, the positions of elements in the list that are equal to it, or the value of any other element in the list. Our protocol can also be applied to verify the existence of vertex-disjoint paths connecting all given pairs of endpoints in any undirected graph.
Aritra Banerjee, Michael Clear, Hitesh Tewari
Zero-knowledge proofs have always provided a clear solution when it comes to conveying information from a prover to a verifier or vice versa without revealing essential information about the process. Advancements in zero-knowledge have helped develop proofs which are succinct and provide non-interactive arguments of knowledge along with maintaining the zero-knowledge criteria. zk-SNARKs (Zero knowledge Succinct Non-Interactive Argument of Knowledge) are one such method that outshines itself when it comes to advancement of zero-knowledge proofs. The underlying principle of the Zcash algorithm is such that it delivers a full-fledged ledger-based digital currency with strong privacy guarantees and the root of ensuring privacy lies fully on the construction of a proper zk-SNARK. In this paper we elaborate and construct a concrete zk-SNARK proof from scratch and explain its role in the Zcash algorithm.
Nai-Hui Chia, Kai-Min Chung, Takashi Yamakawa
In a recent seminal work, Bitansky and Shmueli (STOC '20) gave the first construction of a constant round zero-knowledge argument for NP secure against quantum attacks. However, their construction has several drawbacks compared to the classical counterparts. Specifically, their construction only achieves computational soundness, requires strong assumptions of quantum hardness of learning with errors (QLWE assumption) and the existence of quantum fully homomorphic encryption (QFHE), and relies on non-black-box simulation. In this paper, we resolve these issues at the cost of weakening the notion of zero-knowledge to what is called $\epsilon$-zero-knowledge. Concretely, we construct the following protocols: - We construct a constant round interactive proof for NP that satisfies statistical soundness and black-box $\epsilon$-zero-knowledge against quantum attacks assuming the existence of collapsing hash functions, which is a quantum counterpart of collision-resistant hash functions. Interestingly, this construction is just an adapted version of the classical protocol by Goldreich and Kahan (JoC '96) though the proof of $\epsilon$-zero-knowledge property against quantum adversaries requires novel ideas. - We construct a constant round interactive argument for NP that satisfies computational soundness and black-box $\epsilon$-zero-knowledge against quantum attacks only assuming the existence of post-quantum one-way functions. At the heart of our results is a new quantum rewinding technique that enables a simulator to extract a committed message of a malicious verifier while simulating verifier's internal state in an appropriate sense.
Youssef El Housni, Aurore Guillevic
No abstract is available for this record.