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5,430 results · page 215 of 227
Christina Garman, Matthew Green, Ian Miers, Aviel D. Rubin
No abstract is available for this record.
Sébastien Canard, Iwen Coisel, Amandine Jambert, Jacques Traoré
No abstract is available for this record.
Claudio Orlandi, Rafail Ostrovsky, Vanishree Rao, Amit Sahai · 5 authors
The notion of Zero Knowledge introduced by Goldwasser, Micali and Rackoff in STOC 1985 is fundamental in Cryptography. Motivated by conceptual and practical reasons, this notion has been explored under stronger definitions. We will consider the following two main strengthened notions. Statistical Zero Knowledge: here the zero-knowledge property will last forever, even in case in future the adversary will have unlimited power. Concurrent Non-Malleable Zero Knowledge: here the zero-knowledge property is combined with non-transferability and the adversary fails in mounting a concurrent man-inthe-middle attack aiming at transferring zero-knowledge proofs/arguments. Besides the well-known importance of both notions, it is still unknown whether one can design a zero-knowledge protocol that satisfies both notions simultaneously. In this work we shed light on this question in a very strong sense. We show a statistical concurrent non-malleable zero-knowledge argument system for N P with a black-box simulatorextractor. 1
Jens Groth, Markulf Kohlweiss
Abstract. We construct a 3-move public coin special honest verifier zero-knowledge proof, a so-called Sigma-protocol, for a list of commitments having at least one commit-ment that opens to 0. It is not required for the prover to know openings of the other commitments. The proof system is efficient, in particular in terms of communication requiring only the transmission of a logarithmic number of commitments. We use our proof system to instantiate both ring signatures and zerocoin, a novel mech-anism for bitcoin privacy. We use our Sigma-protocol as a (linkable) ad-hoc group identi-fication scheme where the users have public keys that are commitments and demonstrate knowledge of an opening for one of the commitments to unlinkably identify themselves (once) as belonging to the group. Applying the Fiat-Shamir transform on the group identification scheme gives rise to ring signatures, applying it to the linkable group iden-tification scheme gives rise to zerocoin. Our ring signatures are very small compared to other ring signature schemes and we only assume the users ’ secret keys to be the discrete logarithms of single group elements so the setup is quite realistic. Similarly, compared with the original zerocoin protocol we rely on a weak cryptographic assumption and do not require a trusted setup. A third application of our Sigma protocol is an efficient proof of membership of a secret committed value u belonging to a public list L = {λ1,..., λN}.
Sébastien Canard, David Pointcheval, Olivier Sanders
International audience
Elli Androulaki, Ghassan Karame
No abstract is available for this record.
Siddharth Prakash Rao
In this paper we discuss Bitcoin, the leader among the existing cryptocurrencies, to analyse its trends, success factors, current challenges and probable solutions to make it even better. In the introduction section, we discuss the history and working mechanism of Bitcoin. In the background section, we develop the ideas that evolved in the process of making a stable cryptocurrency. We also analyze the survey matrices of the present day cryptocurrencies. This survey clearly shows that Bitcoin is the clear winner among its kind. Section 3 is about the success factors of Bitcoin and the proceeding sections are a discussion about current challenges which pose as hurdles in making Bitcoin a better currency in the digital world. We finally discuss the balance between anonymity and reduced trust in the cryptocurrency world, before concluding the survey.
Fabrice Benhamouda, Stephan Krenn, Vadim Lyubashevsky, Krzysztof Pietrzak
Abstract. We design an efficient commitment scheme, and companion zero-knowledge proofs of knowledge, based on the learning with errors over rings (RLWE) problem. In particular, for rings in which almost all elements have inverses, we construct a perfectly binding commitment scheme whose hiding property relies on the RLWE assumption. Our scheme maps elements from the ring (or equivalently, n elements from Fq) to a small constant number of ring elements. We then construct Σ-protocols for proving, in a zero-knowledge manner, knowledge of the message contained in a commitment. We are able to further extend our basic protocol to allow us to prove additive and multiplicative relations among committed values. Our protocols have a communication complexity of O(Mn log q) and achieve a negligible knowledge error in one run. Here M is the constant from a rejection sampling technique that we employ, and can be set close to 1 by adjusting other parameters. Previously known Σ-protocols for LWE-related languages either relied on “smudging ” out the error (which necessitates working over large fields, resulting in poor efficiency) or only achieved a noticeable or even constant knowledge error (thus requiring many repetitions of the protocol).
Fabrice Benhamouda, Jan Camenisch, Stephan Krenn, Vadim Lyubashevsky · 5 authors
No abstract is available for this record.
Benjamin Johnson, Áron Lászka, Jens Großklags, Marie Vasek · 5 authors
No abstract is available for this record.
Iddo Bentov, Ranjit Kumaresan
We study a model of fairness in secure computation in which an adversarial party that aborts on receiving output is forced to pay a mutually predefined monetary penalty. We then show how the Bitcoin network can be used to achieve the above notion of fairness in the two-party as well as the multiparty setting (with a dishonest majority). In particular, we propose new ideal functionalities and protocols for fair secure computation and fair lottery in this model. One of our main contributions is the definition of an ideal primitive, which we call F?CR (CR stands for “claim-or-refund”), that formalizes and abstracts the exact properties we require from the Bitcoin network to achieve our goals. Naturally, this abstraction allows us to design fair protocols in a hybrid model in which parties have access to the F?CR functionality, and is otherwise independent of the Bitcoin ecosystem. We also show an efficient realization of F?CR that requires only two Bitcoin transactions to be made on the network. Our constructions also enjoy high efficiency. In a multiparty setting, our protocols only require a constant number of calls to F?CR per party on top of a standard multiparty secure computation protocol. Our fair multiparty lottery protocol improves over previous solutions which required a quadratic number of Bitcoin transactions.
Philip Koshy, Diana Koshy, Patrick McDaniel
No abstract is available for this record.
Hongda Li, Dengguo Feng
No abstract is available for this record.
Zhaokai Luo, Wenfeng Shen, Luokai Hu
With the rise and extensive usage of Bit coin, a peer-to-peer electronic cash system beginning at 2008, the number of transactions is growing. In order to analyze the activity in this currency system, we present a parallel analysis approach for meeting the need of building the transaction graph of this financial system. In order to test the performance and the realistic possibility of our approach, we implemented our approach and conducted some comparing to test the performance of our system. Through the experiment, we confirmed that this method is highly efficient and reliable compared with the traditional method.
Masayuki Abe, Jan Camenisch, Maria Dubovitskaya, Ryo Nishimaki
In this paper, we provide the first scheme that realises an attribute-based access control system for static resources that offers maximal privacy and is secure in the universal composability framework (UC). More precisely, we offer a protocol for adaptive oblivious transfer, where the sender can enforce an attribute-based access control policy for each record and nevertheless learns neither which record a user retrieves nor which attributes a user has. As additional results we provide a new structure-preserving signature scheme from the SXDH assumption and a new universally composable adaptive oblivious transfer protocol that is secure under two DDH-like assumptions and is the most efficient one secure under ``non $q$-type'' assumptions. We believe the new signature scheme to be of independent interest as a building block that is compatible with Groth-Sahai non-interactive zero-knowledge proofs.
Antonis Papadimitriou, Mingchen Zhao, Andreas Haeberlen
In this paper, we discuss the problem of detecting general faults in distributed systems that handle confidential information. Detecting non-crash faults is difficult in this setting because, to check the behavior of a given node, we need to know its expected behavior -- but that can depend on the confidential information. Classical zero-knowledge proofs are difficult to apply because they are designed to verify functions with a fixed number of inputs, but in many distributed systems, both the size and the number of a node's "inputs" (the messages it has received from other nodes) are not known.
Udo Kroon
This paper introduces a new information technology: ma3tch (autonomous anonymous analysis). Ma3tch enables virtual information integration to build a `dynamic networked collective intelligence' without infringing upon security, confidentiality, privacy and/or data protection regulations. It provides organizations with information and knowledge advantages. The ma3tch technology is empowered by a decentralized information oriented architecture: a `privacy by design' framework that uses distributed agents to facilitate decentralized but integrated information access, processing and analysis. It shapes a `virtual information cloud' between autonomous organizations that enables secure, integral and intelligent real time information analysis. Relevant information and knowledge distributed between autonomous organizations is automatically detected and applied throughout the network as soon as it emerges. The dynamic design principles allow practically any type of (cross domain) information to be virtually integrated: government, commercial, intelligence, law enforcement, financial, telecom, biomedical, compliance, etc., without infringing privacy, confidentiality, security or data protection rules and regulations. It advances both privacy AND knowledge beyond conventional limitations.
Kai-Min Chung, Huijia Lin, Rafael Pass
We present a constant-round concurrent zero-knowledge protocol for NP. Our protocol relies on the existence of families of collision-resistant hash functions, and a new, but in our eyes, natural complexity-theoretic assumption: the existence of P-certificates-that is, "succinct" non-interactive proofs/arguments for P. As far as we know, our results yield the first constant-round concurrent zero-knowledge protocol for NP with an explicit zero-knowledge simulator based on any assumption.
Sung-Wook Park, Im-Yeong Lee
Recently, smart devices for various services have been developed using converged telecommunications, and the markets for near field communication mobile services is expected to grow rapidly. In particular, the realization of mobile NFC payment services is expected to go commercial, and it is widely attracting attention both on a domestic and global level. However, this realization would increase privacy infringement, as personal information is extensively used in the NFC technology. One example of such privacy infringement would be the case of the Google wallet service. In this paper, we propose an zero-knowledge proof scheme and ring signature based on NTRU for protecting user information in NFC mobile payment systems without directly using private financial information of the user.
Zongyang Zhang, Zhenfu Cao, Haojin Zhu
No abstract is available for this record.
Xiyu Pang, Cheng Wang, Yuhong Zhang
On the basis of analyzing the shortcomings of traditional authentication mechanism synthetically, the paper presents a new kind of P2P identity authentication model. In the new P2P Identity authentication model, it authenticates the identity of nodes by using a new Zero-Knowledge proof identification scheme which combines the advantage of RSA. Besides, during the process of validating nodes ’ identity, CA (Center Authentication) doesn’t need to participate in. At last, Simulation results show that the new P2P identity authentication method can improve the safety of network effectively.
Hui Cui, Yi Mu, Man Ho Au
Consider a practical scenario: an untrusted gate-way is required to verify all the incoming information en-crypted via an encryption scheme, while the sender does not want to reveal any information about the plaintext and the privileged user to the gateway. That is, the gateway distributes the information to a predefined group of users and only the privileged user can open the message. To solve this problem, we need an access control mechanism to allow certain specification of the access control policies while protecting the users' privacy. With this scenario in mind, we propose the notion of verifiable and anonymous encryption where a verification function is added to the ciphertext, which captures the security requirements of the confidentiality of the plaintext and the anonymity of the privileged user. We present two specific constructions of our framework under the setting of asymmetric bilinear pairings in this paper. Our first scheme is proven confidential and anonymous under a weaker security model in the random oracle model, and our second one is built on the basis of a zero knowledge proof of knowledge under a strong security game.
Kai-Min Chung, Daniel Dadush, Feng-Hao Liu, Chris Peikert
The smoothing parameter $η_ε(\mathcal{L})$ of a Euclidean lattice $\mathcal{L}$, introduced by Micciancio and Regev (FOCS'04; SICOMP'07), is (informally) the smallest amount of Gaussian noise that "smooths out" the discrete structure of $\mathcal{L}$ (up to error $ε$). It plays a central role in the best known worst-case/average-case reductions for lattice problems, a wealth of lattice-based cryptographic constructions, and (implicitly) the tightest known transference theorems for fundamental lattice quantities. In this work we initiate a study of the complexity of approximating the smoothing parameter to within a factor $γ$, denoted $γ$-${\rm GapSPP}$. We show that (for $ε= 1/{\rm poly}(n)$): $(2+o(1))$-${\rm GapSPP} \in {\rm AM}$, via a Gaussian analogue of the classic Goldreich-Goldwasser protocol (STOC'98); $(1+o(1))$-${\rm GapSPP} \in {\rm coAM}$, via a careful application of the Goldwasser-Sipser (STOC'86) set size lower bound protocol to thin spherical shells; $(2+o(1))$-${\rm GapSPP} \in {\rm SZK} \subseteq {\rm AM} \cap {\rm coAM}$ (where ${\rm SZK}$ is the class of problems having statistical zero-knowledge proofs), by constructing a suitable instance-dependent commitment scheme (for a slightly worse $o(1)$-term); $(1+o(1))$-${\rm GapSPP}$ can be solved in deterministic $2^{O(n)} {\rm polylog}(1/ε)$ time and $2^{O(n)}$ space. As an application, we demonstrate a tighter worst-case to average-case reduction for basing cryptography on the worst-case hardness of the ${\rm GapSPP}$ problem, with $\tilde{O}(\sqrt{n})$ smaller approximation factor than the ${\rm GapSVP}$ problem. Central to our results are two novel, and nearly tight, characterizations of the magnitude of discrete Gaussian sums.
Xiaoqiang Guo, Shuai Zhang, Ying Li
With the advent of the information age, the network security is particularly important. The secure multiparty computation is a very important branch of cryptography. It is a hotspot in the field of information security. It expanded the scope of the traditional distributed computing and information security, provided a new computing model for the network collaborative computing. First we introduced several key technologies of secure multiparty computation: secret sharing and verifiable secret sharing, homomorphic public key cryptosystem, mix network, zero knowledge proof, oblivious transfer, millionaire protocol. Second we discussed the applications of secure multiparty computation in electronic voting, electronic auctions, threshold signature, database queries, data mining, mechanical engineering and other fields.