Blockchain Papers

Dakshita Khurana, Muhammad Haris Mughees

No abstract is available for this record.

Shuichi Katsumata, Ryo Nishimaki, Shota Yamada, Takashi Yamakawa

No abstract is available for this record.

Hui Cui, Zhiguo Wan, Xinlei Wei, ‪Surya Nepal‬ · 5 authors

The concept of functional encryption (FE) has been introduced to address the shortcomings of public-key encryption (PKE) in many emerging applications which require both data storage and data sharing (e.g., cloud storage service). One of the major issues existing in most FE schemes is the efficiency, as they are built from bilinear pairings of which the computation is very expensive. A widely accepted solution to this problem is outsourcing the heavy workloads to a powerful third party and leaving the user with the light computation. Nevertheless, it is impractical to assume that the third party (e.g., the cloud) will provide free services. To our knowledge, no attention has been paid to the payment procedure between the user and the third party in an FE with outsourced decryption (FEOD) scheme under the assumption that neither of them should be trusted. Leveraging the transactions on cryptocurrencies supported by the blockchain technology, in this paper, we aim to design FE with payable outsourced decryption (FEPOD) schemes. The payment in an FEPOD scheme is achieved through a blockchain-based cryptocurrency, which enables the user to pay a third party when it correctly completes the outsourced decryption. We define the adversarial model for FEPOD schemes, and then present a generic construction of FEPOD schemes. Also, we evaluate the performance of the proposed generic construction by implementing a concrete FEPOD scheme over a blockchain platform.

Saikrishna Badrinarayanan, Rex Fernando, Aayush Jain, Dakshita Khurana · 5 authors

No abstract is available for this record.

Benoît Libert, Khoa Nguyen, Alain Passelègue, Radu Ţiţiu

No abstract is available for this record.

Ahmed E. Kosba, Dimitrios Papadopoulos, Charalampos Papamanthou, Dawn Song

The last few years have witnessed increasing interest in the deployment of zero-knowledge proof systems, in particular ones with succinct proofs and efficient verification (zk-SNARKs). One of the main challenges facing the wide deployment of zk-SNARKs is the requirement of a trusted key generation phase per different computation to achieve practical proving performance. Existing zero-knowledge proof systems that do not require trusted setup or have a single trusted preprocessing phase suffer from increased proof size and/or additional verification overhead. On the other other hand, although universal circuit generators for zk-SNARKs (that can eliminate the need for per-computation preprocessing) have been introduced in the literature, the performance of the prover remains far from practical for real-world applications. In this paper, we first present a new zk-SNARK system that is well-suited for randomized algorithms-in particular it does not encode randomness generation within the arithmetic circuit allowing for more practical prover times. Then, we design a universal circuit that takes as input any arithmetic circuit of a bounded number of operations as well as a possible value assignment, and performs randomized checks to verify consistency. Our universal circuit is linear in the number of operations instead of quasi-linear like other universal circuits. By applying our new zk-SNARK system to our universal circuit, we build MIRAGE, a universal zk-SNARK with very succinct proofs-the proof contains just one additional element compared to the per-circuit preprocessing state-of-the-art zk-SNARK by Groth (Eurocrypt 2016). Finally, we implement MIRAGE and experimentally evaluate its performance for different circuits and in the context of privacy-preserving smart contracts. © 2020 by The USENIX Association. All Rights Reserved.

Hanwen Feng, Jianwei Liu, Qianhong Wu, Yanan Li

No abstract is available for this record.

Thomas Attema, Ronald Cramer

No abstract is available for this record.

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

Marshall Ball, Dana Dachman-Soled, Mukul Kulkarni

No abstract is available for this record.

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.

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.

Geoffroy Couteau, Dominik Hartmann

We put forth a new framework for building pairing-based non-interactive zero-knowledge (\(\mathsf {NIZK}\)) arguments for a wide class of algebraic languages, which are an extension of linear languages, containing disjunctions of linear languages and more. Our approach differs from the Groth-Sahai methodology, in that we rely on pairings to compile a \(\varSigma \)-protocol into a \(\mathsf {NIZK}\). Our framework enjoys a number of interesting features: conceptual simplicity, parameters derive from the \(\varSigma \)-protocol; proofs as short as resulting from the Fiat-Shamir heuristic applied to the underlying \(\varSigma \)-protocol; fully adaptive soundness and perfect zero-knowledge in the common random string model with a single random group element as CRS; yields simple and efficient two-round, public coin, publicly-verifiable perfect witness-indistinguishable (WI) arguments(ZAPs) in the plain model. To our knowledge, this is the first construction of two-rounds statistical witness-indistinguishable arguments from pairing assumptions.

Thomas Attema, Vadim Lyubashevsky, Gregor Seiler

No abstract is available for this record.

Carsten Baum, Ariel Nof

No abstract is available for this record.

Kyosuke Yamashita, Mehdi Tibouchi, Masayuki Abe

No abstract is available for this record.

Hila Dahari, Yehuda Lindell

No abstract is available for this record.

Maharage Nisansala Sevwandi Perera, Toru Nakamura, Masayuki Hashimoto, Hiroyuki Yokoyama

No abstract is available for this record.

Oded Goldreich, Liav Teichner

We initiate a study of super-perfect zero-knowledge proof systems. Loosely speaking, these are proof systems for which the interaction can be perfectly simulated in strict probabilistic polynomial-time. In contrast, the standard definition of perfect zero-knowledge only requires that the interaction can be perfectly simulated by a strict probabilistic polynomial-time that is allowed to fail with probability at most one half. We show that two types of perfect zero-knowledge proof systems can be transformed into super-perfect ones. The first type includes the perfect zero-knowledge interactive proof system for Graph Isomorphism and other systems of the same form, including perfect zero-knowledge arguments for NP. The second type refers to perfect non-interactive zero-knowledge proof sys-tems. We also present a super-perfect non-interactive zero-knowledge proof system for the set

Yang Tao, Xi Wang, Rui Zhang

No abstract is available for this record.

Elette Boyle, Niv Gilboa, Yuval Ishai, Ariel Nof

Secure computation protocols enable mutually distrusting parties to compute a function of their private inputs while revealing nothing but the output. Protocols with full security (also known as guaranteed output delivery) in particular protect against denial-of-service attacks, guaranteeing that honest parties receive a correct output. This feature can be realized in the presence of an honest majority, and significant research effort has gone toward attaining full security with good asymptotic and concrete efficiency.

Vadim Lyubashevsky, Ngoc Khanh Nguyen, Gregor Seiler

We present a novel lattice-based zero-knowledge proof system for showing that (arbitrary-sized) committed integers satisfy additive and multiplicative relationships. The proof sizes of our schemes are between two to three orders of magnitude smaller than in the lattice proof system of Libert et al. (CRYPTO 2018) for the same relations. Because the proof sizes of our protocols grow linearly in the integer length, our proofs will eventually be longer than those produced by quantum-safe succinct proof systems for general circuits (e.g. Ligero, Aurora, etc.). But for relations between reasonably-sized integers (e.g. $512$-bit), our proofs still result in the smallest zero-knowledge proof system based on a quantum-safe assumption. Of equal importance, the run-time of our proof system is at least an order of magnitude faster than any other quantum-safe scheme.

David Heath, Vladimir Kolesnikov

Zero-knowledge (ZK) proofs (ZKP) have received wide attention, focusing on non-interactivity, short proof size, and fast verification time. We focus on the fastest total proof time, in particular for large Boolean circuits. Under this metric, Garbled Circuit (GC)-based ZKP (Jawurek et al., [JKO], CCS 2013) remained the state-of-the-art technique due to the low-constant linear scaling of computing the garbling.

Alin Tomescu, Ittai Abraham, Vitalik Buterin, Justin Drake · 6 authors

No abstract is available for this record.