Blockchain Papers

Jens Groth, Mary Maller

No abstract is available for this record.

Irene Giacomelli, Jesper Madsen, Claudio Orlandi

In this paper we describe ZKBoo ¹, a proposal for practically efficient zero-knowledge arguments especially tailored for Boolean circuits and report on a proof-of-concept implementation. As an highlight, we can generate (resp. verify) a non-interactive proof for the SHA-1 circuit in approximately 13ms (resp. 5ms), with a proof size of 444KB. Our techniques are based on the “MPC-in-the-head” approach to zero-knowledge of Ishai et al. (IKOS), which has been successfully used to achieve significant asymptotic improvements. Our contributions include: ◦ A thorough analysis of the different variants of IKOS, which highlights their pros and cons for practically relevant soundness parameters; ◦ A generalization and simplification of their approach, which leads to faster Σ-protocols (that can be made non-interactive using the Fiat-Shamir heuristic) for statements of the form “I know x such that y = φ(x)” (where φ is a circuit and y a public value); ◦ A case study, where we provide explicit protocols, implementations and benchmarking of zero-knowledge protocols for the SHA-1 and SHA-256 circuits.

Rafail Ostrovsky, Alessandra Scafuro, Muthuramakrishnan Venkitasubramanian

No abstract is available for this record.

Genqiang Wu, Yeping He, Yi Lu, Liping Ding

Abstract. We consider the following problem: Assuming that Alice and Bob have an integer interval [a, e] and an integer b respectively, for a commitment c to b, Alice and Bob jointly check whether b is within [a, e] without revealing their inputs, where either party may behave malicious-ly. A special case of the problem is the secure integer comparison in the malicious model. This problem mainly arises from location-based access control systems where one party needs to assure to the other party that its location is within some definite area. Our main result is a constant-round protocol that exhibit the square of log e communication and the square of log e exponentiations with simulation-based security. At the heart of the construction is perfec-t k-ary index and corresponding zero-knowledge proof techniques. We consider a more general case of the problem where the interval is substi-tuted by a union of intervals.

Eli Ben‐Sasson, Alessandro Chiesa, Daniel Genkin, Eran Tromer · 5 authors

No abstract is available for this record.

Abhishek Jain, Stephan Krenn, Krzysztof Pietrzak, Aris Tentes

No abstract is available for this record.

Seiko Arita

Abstract. In resetting attacks against a proof system, a prover or a verifier is reset and enforced to use the same random tape on various inputs as many times as an adversary may want. Recent deployment of cloud computing gives these attacks a new importance. This paper shows that argument systems for any NP language that are both resettably-sound and resettable zero-knowledge are possible by a constant-round protocol in the BPK model. For that sake, we define and construct a resettablyextractable conditional commitment scheme.

Ning Ding, Dawu Gu

No abstract is available for this record.

Imad Fakhri Taha Alshaikhli, Rusydi Hasan Makarin, Siti Khairunnisa Mohd Bakri, Nur Dalilah More Yusoff · 5 authors

Much of the current innovation in advanced materials is occurring at the nanoscale, specifically in manufactured nanomaterials (MNs). MNs display unique attributes and behaviors, and may be biologically and physically unique, making them valuable across a wide range of applications. However, as the number, diversity and complexity of MNs coming to market continue to grow, assessing their health and environmental risks with traditional animal testing approaches is too time- and cost-intensive to be practical, and is undesirable for ethical reasons. New approaches are needed that meet current requirements for regulatory risk assessment while reducing reliance on animal testing and enabling safer-by-design product development strategies to be implemented. The adverse outcome pathway (AOP) framework presents a sound model for the advancement of MN decision making. Yet, there are currently gaps in technical and policy aspects of AOPs that hinder the adoption and use for MN risk assessment and regulatory decision making. This review outlines the current status and next steps for the development and use of the AOP framework in decision making regarding the safety of MNs. Opportunities and challenges are identified concerning the advancement and adoption of AOPs as part of an integrated approach to testing and assessing (IATA) MNs, as are specific actions proposed to advance the development, use and acceptance of the AOP framework and associated testing strategies for MN risk assessment and decision making. The intention of this review is to reflect the views of a diversity of stakeholders including experts, researchers, policymakers, regulators, risk assessors and industry representatives on the current status, needs and requirements to facilitate the future use of AOPs in MN risk assessment. It incorporates the views and feedback of experts that participated in two workshops hosted as part of an Organization for Economic Cooperation and Development (OECD) Working Party on Manufactured Nanomaterials (WPMN) project titled, "Advancing AOP Development for Nanomaterial Risk Assessment and Categorization", as well as input from several EU-funded nanosafety research consortia.

Atsuko Miyaji, Mohammad Shahriar Rahman

No abstract is available for this record.

Zongyang Zhang, Zhenfu Cao, Rong Ma

No abstract is available for this record.

Esfandiar Mohammadi

No abstract is available for this record.

Chunming Tang, Zheng‐an Yao

Multi-prover zero-knowledge proof is an interesting proof in which a few provers synchronously prove validity of a statement to an verifier, however, the verifier will learn nothing beyond the fact that the statement is correct. We call multi-prover zero-knowledge proof as multi-prover zero-knowledge arguments if all provers are probabilistic polynomial-time participants. In this paper, we give the formal definition of multi-prover zero-knowledge argument and construct it based on discrete logarithm problem (DLP).

Minh-Huyen Nguyen, Salil Vadhan

We prove that every problem in NP that has a zero-knowledge proof also has a zero-knowledge proof where the prover can be implemented in probabilistic polynomial time given an NP witness. Moreover, if the original proof system is statistical zero knowledge, so is the resulting efficient-prover proof system. An equivalence of zero knowledge and efficient-prover zero knowledge was previously known only under the assumption that one-way functions exist (whereas our result is unconditional), and no such equivalence was known for statistical zero knowledge. Our results allow us to translate the many general results and characterizations known for zero knowledge with inefficient provers to zero knowledge with efficient provers.

Jens Groth, Rafail Ostrovsky, Amit Sahai

No abstract is available for this record.

Ivan Damgård, Serge Fehr, Louis Salvail

The concept of zero-knowledge (ZK) has become of fundamental importance in cryptography. However, in a setting where entities are modeled by quantum computers, classical arguments for proving ZK fail to hold since, in the quantum setting, the concept of rewinding is not generally applicable. Moreover, known classical techniques that avoid rewinding have various shortcomings in the quantum setting.<br /> <br />We propose new techniques for building <em>quantum</em> zero-knowledge (QZK) protocols, which remain secure even under (active) quantum attacks. We obtain computational QZK proofs and perfect QZK arguments for any NP language in the common reference string model. This is based on a general method converting an important class of classical honest-verifier ZK (HVZK) proofs into QZK proofs. This leads to quite practical protocols if the underlying HVZK proof is efficient. These are the first proof protocols enjoying these properties, in particular the first to achieve perfect QZK.<br /> <br />As part of our construction, we propose a general framework for building unconditionally hiding (trapdoor) string commitment schemes, secure against quantum attacks, as well as concrete instantiations based on specific (believed to be) hard problems. This is of independent interest, as these are the first unconditionally hiding string commitment schemes withstanding quantum attacks.<br /> <br />Finally, we give a partial answer to the question whether QZK is possible in the plain model. We propose a new notion of QZK, <em>non-oblivious verifier</em> QZK, which is strictly stronger than honest-verifier QZK but weaker than full QZK, and we show that this notion can be achieved by means of efficient (quantum) protocols.

Boaz Barak, Yehuda Lindell

The notion of efficient computation is usually identified in cryptography and complexity with probabilistic polynomial time. However, until recently, in order to obtain constant-round zero-knowledge proofs and proofs of knowledge (for NP), one had to allow simulators and knowledge-extractors to run in time which is only polynomial on the average (i.e., expected polynomial time). Whether or not allowing expected polynomial-time is necessary for obtaining constant-round zero-knowledge proofs and proofs of knowledge, has been posed as an important open question. This question is interesting not only for its theoretical ramifications, but also because expected polynomial time simulation is not closed under composition. Therefore, in some cases security is not maintained when a protocol that utilizes expected polynomial time simulation (or extraction) is used as a part of a larger protocol.A partial answer to the question of the necessity (or non-necessity) of expected polynomial-time was provided recently by Barak, who gave the first constant-round zero-knowledge argument with a strict (in contrast to expected) polynomial-time simulator. His was also the first protocol that is not black-box zero-knowledge. That is, the simulator in his protocol utilizes the description of the code of the verifier in an essential way.In this paper, we completely resolve the question of expected polynomial-time in zero-knowledge arguments and arguments of knowledge. First, we show that there exist constant-round zero-knowledge arguments of knowledge with strict polynomial-time extractors. As in the simulator of Barak's zero-knowledge protocol, the extractor for our proof of knowledge is not black-box and uses the code of the prover in an essential way.On the negative side, we show that non-black-box techniques are essential to both strict polynomial-time simulation and extraction. That is, we show that no constant-round zero-knowledge argument (or proof) can have a strict polynomial-time black-box simulator. Similarly, we show that no constant-round zero-knowledge argument (or proof) of knowledge can have a strict polynomial-time black-box knowledge extractor. Thus, for constant-round black-box zero-knowledge arguments (resp., arguments of knowledge), it is imperative that the simulator (resp., extractor) be allowed to run in expected polynomial-time.

Mike Burmester, Yvo Desmedt

No abstract is available for this record.