Blockchain Papers

Charanjit S. Jutla, Arnab Roy

No abstract is available for this record.

Keisuke Hara, Fuyuki Kitagawa, Takahiro Matsuda, Goichiro Hanaoka · 5 authors

No abstract is available for this record.

Sanjam Garg, Mohammad Hajiabadi, Mohammad Mahmoody, Ameer Mohammed

No abstract is available for this record.

Yael Tauman Kalai, Dakshita Khurana, Amit Sahai

No abstract is available for this record.

Seongseop Kim, David J. Wu

Non-interactive zero-knowledge (NIZK) proofs are fundamental to modern cryptography. Numerous NIZK constructions are known in both the random oracle and the common reference string (CRS) models. In the CRS model, there exist constructions from several classes of cryptographic assumptions such as trapdoor permutations, pairings, and indistinguishability obfuscation. However, at the time of the initial publication of this work, we did not have constructions of NIZKs from standard lattice assumptions. In this work, we take an initial step toward constructing multi-theorem NIZKs for general $$\mathsf {NP}$$ languages from standard lattice assumptions by considering a relaxation to the preprocessing model and a new model we call the designated-prover model. In the preprocessing model, a setup algorithm generates secret proving and verification keys for the prover and the verifier, respectively. In the designated-prover model, the proving key is secret, but the verification key is public. In both settings, the proving key is used to construct proofs and the verification key is used to check proofs. Finally, in the multi-theorem setting, both the proving and verification keys should be reusable for an unbounded number of theorems without compromising soundness or zero-knowledge. Previous constructions of NIZKs in the preprocessing model that rely on weaker assumptions like one-way functions or oblivious transfer are only secure in a single-theorem setting. Thus, constructing multi-theorem NIZKs in these relaxed models does not seem to be inherently easier than constructing them in the CRS model. In this work, we first construct a multi-theorem preprocessing NIZK argument from context-hiding homomorphic signatures. In fact, the construction is a designated-prover NIZK. We also show that using homomorphic commitments, we can get statistically sound proofs in the preprocessing and designated-prover models. Together with lattice-based instantiations of homomorphic signatures and commitments, we obtain the first multi-theorem NIZKs in the preprocessing and designated-prover models from standard lattice assumptions. Finally, we show how to generalize our construction to obtain a universally composable NIZK (UC-NIZK) in the preprocessing model from standard lattice assumptions. Our UC-NIZK relies on a simple preprocessing protocol based on a new primitive we call blind homomorphic signatures.

Carsten Baum, Huang Lin, Sabine Oechsner

No abstract is available for this record.

Fucai Luo, Kunpeng Wang

No abstract is available for this record.

Sharon Goldberg, Leonid Reyzin, Omar Sagga, Foteini Baldimtsi

In many applications, it is important to verify that an RSA public key (N; e) speci es a
\npermutation over the entire space ZN, in order to prevent attacks due to adversarially-generated
\npublic keys. We design and implement a simple and e cient noninteractive zero-knowledge
\nprotocol (in the random oracle model) for this task. Applications concerned about adversarial
\nkey generation can just append our proof to the RSA public key without any other modi cations
\nto existing code or cryptographic libraries. Users need only perform a one-time veri cation of
\nthe proof to ensure that raising to the power e is a permutation of the integers modulo N. For
\ntypical parameter settings, the proof consists of nine integers modulo N; generating the proof
\nand verifying it both require about nine modular exponentiations.
\nWe extend our results beyond RSA keys and also provide e cient noninteractive zero-
\nknowledge proofs for other properties of N, which can be used to certify that N is suitable
\nfor the Paillier cryptosystem, is a product of two primes, or is a Blum integer. As compared to
\nthe recent work of Auerbach and Poettering (PKC 2018), who provide two-message protocols for
\nsimilar languages, our protocols are more e cient and do not require interaction, which enables
\na broader class of applications.

Melissa Chase, Yevgeniy Dodis, Yuval Ishai, Daniel Kraschewski · 7 authors

We consider the problem of Non-Interactive Two-Party Secure Computation (NISC), where Rachel wishes to publish an encryption of her input x, in such a way that any other party, who holds an input y, can send her a single message which conveys to her the value f(x, y), and nothing more. We demand security against malicious parties. While such protocols are easy to construct using garbled circuits and general non-interactive zero-knowledge proofs, this approach inherently makes a non-black-box use of the underlying cryptographic primitives and is infeasible in practice.

Rafail Ostrovsky, Giuseppe Persiano, Daniele Venturi, Ivan Visconti

No abstract is available for this record.

Georg Fuchsbauer, Eike Kiltz, Julian Loss

No abstract is available for this record.

Fabrice Benhamouda, Olivier Blazy, Léo Ducas, Willy Quach

No abstract is available for this record.

Jonathan Bootle, Andrea Cerulli, Jens Groth, S. Jakobsen · 5 authors

No abstract is available for this record.

Jonathan Katz, Vladimir Kolesnikov, Xiao Wang

Recent work, including ZKBoo, ZKB++, and Ligero, has developed efficient non-interactive zero-knowledge proofs of knowledge (NIZKPoKs) for Boolean circuits based on symmetric-key primitives alone, using the "MPC-in-the-head" paradigm of Ishai et al. We show how to instantiate this paradigm with MPC protocols in the preprocessing model; once optimized, this results in an NIZKPoK with shorter proofs (and comparable computation) as in prior work for circuits containing roughly 300--100,000 AND~gates. In contrast to prior work, our NIZKPoK also supports witness-independent preprocessing, which allows the prover to shift most of its work to an offline phase before the witness is known. We use our NIZKPoK to construct a signature scheme based only on symmetric-key primitives (and hence with "post-quantum" security). The resulting scheme has shorter signatures than the scheme built using ZKB++ (and comparable signing/verification time), and is even competitive with hash-based signature schemes. To further highlight the flexibility and power of our NIZKPoK, we also use it to build efficient ring and group signatures based on symmetric-key primitives alone. To our knowledge, the resulting schemes are the most efficient constructions of these primitives that offer post-quantum security.

Christopher Carr, Anamaria Costache, Gareth T. Davies, Kristian Gjøsteen · 5 authors

No abstract is available for this record.

Trishita Tiwari, David Starobinski, Ari Trachtenberg

No abstract is available for this record.

Nils Fleischhacker, Vipul Goyal, Abhishek Jain

We study the round complexity of zero-knowledge (ZK) proof systems. While five round ZK proofs for \({\mathsf {NP}}\) are known from standard assumptions [Goldreich-Kahan, J. Cryptology’96], Katz [TCC’08] proved that four rounds are insufficient for this task w.r.t. black-box simulation. In this work, we study the feasibility of ZK proofs using non-black-box simulation. Our main result is that three round private-coin ZK proofs for \({\mathsf {NP}}\) do not exist (even w.r.t. non-black-box simulation), under certain assumptions on program obfuscation. Our approach builds upon the recent work of Kalai et al. [Crypto’17] who ruled out constant round public-coin ZK proofs under the same assumptions as ours.

David Derler, Sebastian Ramacher, Daniel Slamanig

No abstract is available for this record.

Tao Li, Donghwa Shin, Baolian Wang

Abstract We document numerous occurrences of pump-and-dump schemes (P&Ds) targeting cryptocurrencies, which tend to trigger short-term episodes that feature dramatic increases in prices, volume, and volatility, followed by quick reversals. The evidence we document, including price run-ups before P&Ds start, suggests wealth transfers from outsiders to insiders. Our findings based on wallet-level data are consistent with the reasoning that gambling preferences, overconfidence, and naïve reinforcement learning help explain P&D participation. Finally, exploiting two natural experiments in which exchanges altered P&D policies, we find evidence consistent with the idea that P&Ds contribute to reduced cryptocurrency liquidity and lower prices.

Huige Li, Fangguo Zhang, Jiejie He, Haibo Tian

At present, the cloud storage used in searchable symmetric encryption schemes (SSE) is provided in a private way, which cannot be seen as a true cloud. Moreover, the cloud server is thought to be credible, because it always returns the search result to the user, even they are not correct. In order to really resist this malicious adversary and accelerate the usage of the data, it is necessary to store the data on a public chain, which can be seen as a decentralized system. As the increasing amount of the data, the search problem becomes more and more intractable, because there does not exist any effective solution at present. In this paper, we begin by pointing out the importance of storing the data in a public chain. We then innovatively construct a model of SSE using blockchain(SSE-using-BC) and give its security definition to ensure the privacy of the data and improve the search efficiency. According to the size of data, we consider two different cases and propose two corresponding schemes. Lastly, the security and performance analyses show that our scheme is feasible and secure.

Long-Hai Li, Chengqiang Huang, Shao-Feng Fu

A mix-net is an important cryptographic tool in schemes requiring anonymity of messages, such as in secure e-voting and e-auction schemes. In this paper, we present a novel mix-net protocol which achieves stronger security and satisfies both public verifiability and sender verifiability. Our mix-net is constructed based on Wikström's scheme and strengthens its se-curity by introducing an improved key generation procedure and proposing a new method for constructing zero knowledge proof of secret shuffle. It is proved to be CCA-secure under the assumption of random oracle. Compared with previous mix-net schemes which are CCA-secure, the proposed protocol does not require any trusted center, and incurs fewer inter-actions between servers which resulting in a lower computation and communication complexity.

Alican Beydemir, İbrahim Soğukpınar

Importance of Internet of Things technologies increased in recent years. However, these technologies carry some security vulnerabilities because of their network communication layer. The root cause of these vulnerabilities is usually the Authentication problem. Zero knowledge proof method is a strong cryptographic solution for Authentication problem that is proving of having a knowledge to another party without revealing anything other than the veracity of the statement. Zero knowledge proof method is consist of two-way complex mathematical algorithms for both parties. In this work, a new method that uses zero knowledge proofs has been proposed to provide efficient solution for Internet of Things technologies. New method was implemented and tested, then compared with existing proposed zero knowledge proof based authentication methods.

Rifa Hanifatunnisa, Budi Rahardjo

Increasingly digital technology in the present helped many people lives. Unlike the electoral system, there are many conventional uses of paper in its implementation. The aspect of security and transparency is a threat from still widespread election with the conventional system (offline). General elections still use a centralized system, there is one organization that manages it. Some of the problems that can occur in traditional electoral systems is with an organization that has full control over the database and system, it is possible to tamper with the database of considerable opportunities. Blockchain technology is one of solutions, because it embraces a decentralized system and the entire database are owned by many users. Blockchain itself has been used in the Bitcoin system known as the decentralized Bank system. By adopting blockchain in the distribution of databases on e-voting systems can reduce one of the cheating sources of database manipulation. This research discusses the recording of voting result using blockchain algorithm from every place of election. Unlike Bitcoin with its Proof of Work, this thesis proposed a method based on a predetermined turn on the system for each node in the built of blockchain.

Authors unavailable

This document describes the Schnorr non-interactive zero-knowledge (NIZK) proof, a non-interactive variant of the three-pass Schnorr identification scheme. The Schnorr NIZK proof allows one to prove the knowledge of a discrete logarithm without leaking any information about its value. It can serve as a useful building block for many cryptographic protocols to ensure that participants follow the protocol specification honestly. This document specifies the Schnorr NIZK proof in both the finite field and the elliptic curve settings.