Follow blockchain research across journals, conferences, and preprint repositories.
9,005 results · page 310 of 376
Patrick McCorry, Siamak F. Shahandashti, Feng Hao
No abstract is available for this record.
Jeppe Hallgren, Malte Hallgren, S. S. Fisher, Nicolai Garhøj Larsen · 5 authors
No abstract is available for this record.
Christina Garman, Matthew Green, Ian Miers
No abstract is available for this record.
Rafael Pass, Elaine Shi
Consensus, or state machine replication is a foundational building block of distributed systems and modern cryptography. Consensus in the classical, "permissioned" setting has been extensively studied in the 30 years of distributed systems literature. Recent developments in Bitcoin and other decentralized cryptocurrencies popularized a new form of consensus in a "permissionless" setting, where anyone can join and leave dynamically, and there is no a-priori knowledge of the number of consensus nodes. So far, however, all known permissionless consensus protocols assume network synchrony, i.e., the protocol must know an upper bound of the network's delay, and transactions confirm slower than this a-priori upper bound. We initiate the study of the feasibilities and infeasibilities of achieving responsiveness in permissionless consensus. In a responsive protocol, the transaction confirmation time depends only on the actual network delay, but not on any a-priori known upper bound such as a synchronous round. Classical protocols in the partial synchronous and asynchronous models naturally achieve responsiveness, since the protocol does not even know any delay upper bound. Unfortunately, we show that in the permissionless setting, consensus is impossible in the asynchronous or partially synchronous models. On the positive side, we construct a protocol called Hybrid Consensus by combining classical-style and blockchain-style consensus. Hybrid Consensus shows that responsiveness is nonetheless possible to achieve in permissionless consensus (assuming proof-of-work) when 1) the protocol knows an upper bound on the network delay; 2) we allow a non-responsive warmup period after which transaction confirmation can become responsive; 3) honesty has some stickiness, i.e., it takes a short while for an adversary to corrupt a node or put it to sleep; and 4) less than 1/3 of the nodes are corrupt. We show that all these conditions are in fact necessary - if only one of them is violated, responsiveness would have been impossible. Our work makes a step forward in our understanding of the permissionless model and its differences and relations to classical consensus.
Lewis Tseng
Bitcoin is the most popular cryptocurrency nowadays. Inspired by the success, both industry and academia seek to apply Bitcoin's core technique, Blockchain, to other fields like finance, healthcare and Internet-of-Things. One main application is to use Blockchain as the distributed transaction ledger system, a ledger (or a log) of all transactions that is maintained by anonymous participants in a distributed fashion. For the ledger system, consistency is an important property which specifies how the system orders the transactions. Intuitively, Blockchain is designed to maintain a single ground truth - the chain itself is the order of the transactions that all participants should respect. However, we show that under some circumstances, Bitcoin violates eventual consistency, i.e., participants would not converge to a single chain. Thus, we urge a more thorough study on Bitcoin's consistency properties. At the end of the paper, we propose related research directions.
Dmitry Meshkov, Alexander Chepurnoy, Marc Jansen
No abstract is available for this record.
Chao Yuan, Mixue Xu, Xueming Si
With the rise of Bitcoin, blockchain which is the core technology of Bitcoin has received increasing attention. Privacy preserving and performance on blockchain are two research points in academia and business, but there are still some unresolved issues in both respects. An aggregate signature scheme is a digital signature that supports making signatures on many different messages generated by many different users. Using aggregate signature, the size of the signature could be shortened by compressing multiple signatures into a single signature. In this paper, a new signature scheme for transactions on blockchain based on the aggregate signature was proposed. It was worth noting that elliptic curve discrete logarithm problem and bilinear maps played major roles in our signature scheme. And the security properties of our signature scheme were proved. In our signature scheme, the amount will be hidden especially in the transactions which contain multiple inputs and outputs. Additionally, the size of the signature on transaction is constant regardless of the number of inputs and outputs that the transaction contains, which can improve the performance of signature. Finally, we gave an application scenario for our signature scheme which aims to achieve the transactions of big data on blockchain.
Chao Yuan
With the rise of Bitcoin, cryptographic currencies have attracted more and more attention. Subsequently, other cryptographic currencies were gradually created, such as Zcash, Moreno, Dash and so on. In cryptographic currency, privacy preserving and expansion are two key technical points. In terms of privacy preserving, more effective solutions were proposed in Zcach, Moreno, Dash and other cryptographic currencies systems, in which ring signature, zero knowledge proof and other cryptographic techniques played important roles. But these schemes mainly considered protecting the addresses of both sides of the transaction. In terms of expansion, lightning network and other projects also give solutions. But most of these projects will bring other problems. In this paper, a signature scheme based on the aggregate signature and the elliptic curve algorithm is proposed to hide the transaction value of a single sender and receiver in the transactions which contain multiple inputs and outputs. This signature scheme achieves the purpose of privacy preserving from the transaction value. Further, the correctness proof and security analysis are given in this paper. In addition to that, another signature scheme that combines aggregation signature with bilinear ring signature is proposed. This aggregate ring signature scheme gives another attempt to solve the problem of expansion in the cryptographic currency system only using cryptographic technologies. At the same time, the sender's addresses can be hidden. Similarly, we also confirmed the correctness of this signature scheme.
Veronika Kuchta, Gaurav Sharma, Rajeev Anand Sahu, Olivier Markowitch
No abstract is available for this record.
Saurav Chakraborty, Kaushik Dutta, Don Berndt
No abstract is available for this record.
Ran Canetti, Amit Lichtenberg
The modeling of trapdoor permutations has evolved over the years. Indeed, finding an appropriate abstraction that bridges between the existing candidate constructions and the needs of applications has proved to be challenging. In particular, the notions of certifying permutations (Bellare and Yung, 96), enhanced and doubly enhanced trapdoor permutations (Goldreich, 04, 08, 11, Goldreich and Rothblum, 13) were added to bridge the gap between the modeling of trapdoor permutations and needs of applications. We identify an additional gap in the current abstraction of trapdoor permutations: Previous works implicitly assumed that it is easy to recognize elements in the domain, as well as uniformly sample from it, even for illegitimate function indices. We demonstrate this gap by using the (Bitansky-Paneth-Wichs, 16) doubly-enhanced trapdoor permutation family to instantiate the Feige-Lapidot-Shamir (FLS) paradigm for constructing non-interactive zero-knowledge (NIZK) protocols, and show that the resulting proof system is unsound. To close the gap, we propose a general notion of certifiably injective doubly enhanced trapdoor functions (DECITDFs), which provides a way of certifying that a given key defines an injective function over the domain defined by it, even when that domain is not efficiently recognizable and sampleable. We show that DECITDFs suffice for instantiating the FLS paradigm; more generally, we argue that certifiable injectivity is needed whenever the generation process of the function is not trusted. We then show two very different ways to construct DECITDFs: One is via the traditional method of RSA/Rabin with the Bellare-Yung certification mechanism, and the other using indistinguishability obfuscation and injective pseudorandom generators. In particular the latter is the first candidate injective trapdoor function, from assumptions other than factoring, that suffices for the FLS paradigm. Finally we observe that a similar gap appears also in other paths proposed in the literature for instantiating the FLS paradigm, specifically via verifiable pseudorandom generators and verifiable pseudorandom functions. Closing the gap there can be done in similar ways to the ones proposed here.
Taotao Li, Parhat Abla, Ming‐Sheng Wang, Qianwen Wei
No abstract is available for this record.
Charanjit S. Jutla, Arnab Roy
No abstract is available for this record.
Fabrice Benhamouda, Houda Ferradi, Rémi Géraud, David Naccache
No abstract is available for this record.
Olivier Blazy, Céline Chevalier, Paul Germouty
No abstract is available for this record.
Magnus Gausdal Find, Daniel Smith Tone, Meltem Sönmez Turan
Multiplicative complexity is a complexity measure defined as the minimum number of AND gates required to implement a given primitive by a circuit over the basis (AND, XOR, NOT). Implementations of cyphers with a small number of AND gates are preferred in protocols for fully homomorphic encryption, multiparty computation and zero-knowledge proofs. Fischer and Peralta (2002) computed the number of n-variable Boolean functions with multiplicative complexity 1. In this paper, we study Boolean functions that can be constructed with two AND gates. By characterising the structure of these functions in terms of affine equivalence relations, we provide a closed-form formula for the number of Boolean functions with multiplicative complexity 2.
Meilof Veeningen
Pinocchio is a practical zk-SNARK that allows a prover to perform cryptographically verifiable computations with verification effort potentially less than performing the computation itself. A recent proposal showed how to make Pinocchio adaptive (or “hash-and-prove”), i.e., to enable proofs with respect to computation-independent commitments. This enables computations to be chosen after the commitments have been produced, and for data to be shared between different computations in a flexible way. Unfortunately, this proposal is not zero-knowledge. In particular, it cannot be combined with Trinocchio, a system in which Pinocchio is outsourced to three workers that do not learn the inputs thanks to multi-party computation (MPC). In this paper, we show how to make Pinocchio adaptive in a zero-knowledge way; apply this to make Trinocchio work on computation-independent commitments; present tooling to easily program flexible verifiable computations (with or without MPC); and use it to build a prototype in a medical research case study.
Xuechao Yang, Xun Yi, Caspar Ryan, Ron van Schyndel · 7 authors
No abstract is available for this record.
Daniel Genkin, Yuval Ishai, Mor Weiss
No abstract is available for this record.
Denise Demirel, Lucas Schabhüser, Johannes Buchmann
No abstract is available for this record.
Renming Qi, Chen Feng, Zheng Liu, Nezih Mrad
No abstract is available for this record.
Prabhanjan Ananth, Aloni Cohen, Abhishek Jain
No abstract is available for this record.
Michal Zima
No abstract is available for this record.
Gurinder Singh, Vikas Garg, Pooja Tiwari
Abstract This chapter gives an introduction to blockchain technology which was proposed by the pseudonymous Nakamoto (2008) with his well-known Bitcoin paper to enable online payments in a decentralized digital cash system, solving the double-spending problem where someone can make two payments with the same coin. The chapter starts with an informal outline of the application of a blockchain and a brief explanation of how a blockchain network is able to reach consensus about the common state of a transaction history. Furthermore, it introduces the Proof-of-Work (PoW) algorithmwhich needs to be donein order to extend the blockchain with new blocks. Since the PoW is a very costly computational algorithm, the transaction data is stored in previous blocks resistant to modification, and thus the PoW safeguards the order of blocks, forming a tamper-proof history of transactions. As a last step, it examines the double-spending attack, which is a fundamental attack to the integrity of a blockchain based system.