Follow blockchain research across journals, conferences, and preprint repositories.
5,430 results · page 217 of 227
Endre Bangerter, Stefania Barzan, Stephan Krenn, Ahmad‐Reza Sadeghi · 6 authors
No abstract is available for this record.
Sankita Patel, Viren Patel, Devesh C. Jinwala
No abstract is available for this record.
Man Ho Au, Willy Susilo, Yi Mu, Sherman S. M. Chow
Dynamick-times anonymous authentication (k-TAA) schemes allow members of a group to be authenticated anonymously by application providers for a bounded number of times, where application providers can independently and dynamically grant or revoke access right to members in their own group. In this paper, we construct a dynamick-TAA scheme with space and time complexities ofO(log(k)) and a variant, in which the authentication protocol only requires constant time and space complexities at the cost ofO(k) -sized public key. We also describe some tradeoff issues between different system characteristics. We detail all the zero-knowledge proof-of-knowledge protocols involved and show that our construction is secure in the random oracle model under theq-strong Diffie-Hellman assumption andq-decisional Diffie-Hellman inversion assumption. We provide a proof-of-concept implementation, experiment on its performance, and show that our scheme is practical.
Jannik Dreier, Jean‐Guillaume Dumas, Pascal Lafourcade
Auctions have a long history, having been recorded as early as 500 B.C. [Auction Theory, Academic Press, San Diego, USA, 2002]. Nowadays, electronic auctions have been a great success and are increasingly used in various applications, including high performance computing [Concurrency and Computatio n: Practice and Experience 14(13–15) (2002), 1507–1542]. Many cryptographic protocols have been proposed to address the various security requirements of these electronic transactions, in particular to ensure privacy. Brandt [International Journal of Information Security 5 (2006), 201–216] developed a protocol that computes the winner using homomorphic operations on a distributed ElGamal encryption of the bids. He claimed that it ensures full privacy of the bidders, i.e. no information apart from the winner and the winning price is leaked. We first show that this protocol – when using malleable interactive zero-knowledge proofs – is vulnerable to attacks by dishonest bidders. Such bidders can manipulate the publicly available data in a way that allows the seller to deduce all participants’ bids. We provide an efficient parallelized implementation of the protocol and the attack to show its practicality. Additionally we discuss some issues with verifiability as well as attacks on non-repudiation, fairness and the privacy of individual bidders exploiting authentication problems.
Chengdong Meng, Zhengyong Zhang, Rong Hu, Yongxiang Yang
DAA (Direct Anonymous Attestation) schemes are generally employed with the hardware of TPM to realize anonymous authentication. Basically, DAA schemes are based on group signatures. We propose a new DAA scheme based on a short group signature without encryption which departs from the traditional sign-encrypt-prove paradigm, only adopts an anonymous signature and non-interactive zero knowledge(NIZK) proofs. Compared to other DAA schemes at present, our scheme is approximately the most efficient and computational cost-saving with shorter signature length and easier signature generation. Our scheme also satisfies anonymity, trace ability and non-frame ability requirements.
Jinguang Han, Willy Susilo, Yi Mu, Jun Yan
No abstract is available for this record.
Priti Jagwani, Saroj Kaushik
The increasing trend of embedding positioning capabilities (e.g., GPS) in mobile devices facilitates the widespread use of Location Based Services. For such applications to succeed, privacy and confidentiality are key issues. Over all privacy will have to be managed through a combination of technology, legislation, corporate policy, and social norms. There are many data privacy schemes including Zero Knowledge Proof (ZKP) those can be used for location privacy. ZKP is also useful for removing the bottleneck problem introduced by use of trusted third party. In the earlier work, authors proposed the concept of middleware architecture in which, request and response are not routed through middleware for every transaction. This has reduced the dependency on middleware. This paper presents correspondence between the authentication techniques used in above said architecture and zero knowledge proof technique. Use of the concept of zero knowledge proof for authentication and authorization in the domain of location based services is also explored.
Mark Vinkovits, Erion Elmasllari, Claudio Pastrone
Ubiquitous systems and the Internet of Things (IoT) are on the rise. However, there are issues from businesses and users which hinder the wide-spread application of such systems. In the FP7 EU project ebbits, which deals with integrating IoT into business systems, we collected real-world requirements from participants. From these we designed a complete anonymous network solution including addressing, discovery, authentication and reputation management. Our authentication system relies on Non Interactive Zero Knowledge Proofs augmented for fine granulated access right decisions and accounting. Anonymous reputation is created using reputation tickets, which are obtained through public votings. A reputation ticket is an unforgeable evidence of trustworthiness held by the provider and presented to a consumer on request. Discovery also has to specially be designed for anonymous environments else they leak information about the identity. We provide an attribute based discovery mechanism built with Bloom-filters. Our concept protects privacy but still enables discovery based on partial matches.
Jens Groth, Rafail Ostrovsky, Amit Sahai
Noninteractive zero-knowledge (NIZK) proof systems are fundamental primitives used in many cryptographic constructions, including public-key encryption secure against chosen ciphertext attack, digital signatures, and various other cryptographic protocols. We introduce new techniques for constructing NIZK proofs based on groups with a bilinear map. Compared to previous constructions of NIZK proofs, our techniques yield dramatic reduction in the length of the common reference string (proportional to security parameter) and the size of the proofs (proportional to security parameter times the circuit size). Our novel techniques allow us to answer several long-standing open questions in the theory of noninteractive proofs. We construct the first perfect NIZK argument system for all NP. We construct the first universally composable NIZK argument for all NP in the presence of an adaptive adversary. We construct a non-interactive zap for all NP, which is the first that is based on a standard cryptographic security assumption.
Yue Xiao-han, LI Fu-xiang, Zhou Fu-cai
Direct Anonymous Attestation (DAA) is a special signature scheme that enables remote authentication of a user while preserving privacy under the user's control. Thus, in this paper, based on existing schemes and mechanisms, we firstly construct a DAA signature scheme which is proven secure without random oracles. By making certain reasonable assumptions and employing the techniques of non-interactive zero-knowledge(NIZK) proof system and Two-Party Computation(2PC) scheme, we prove that our scheme satisfies anonymous and untraceable, and compares with existing DAA schemes in the aspects of security and efficiency.
Ke Peng
Chida and Yamamoto propose a batch proof algorithm to enhance the performance of multiple instances of zero knowledge proof of partial knowledge. When multiple instances of zero knowledge proof of partial knowledge need to be proved simultaneously, their proof algorithm employs a batching mechanism to reduce the cost in computation and communication. Unfortunately, their batch proof algorithm is not sound and vulnerable to an attack, which completely breaks soundness of the proof. More precisely, an adversary can design the multiple partial knowledge statements in a special way such that no matter how he is challenged he can always pass the verification as a prover in the batch proof scheme while he does not have the knowledge he claims. The attack is presented and is formally illustrated to always succeed.
Zongyang Zhang, Zhenfu Cao
No abstract is available for this record.
Atsuko Miyaji, Mohammad Shahriar Rahman
Privacy-preserving set operations are useful for many data mining algorithms as building tools. Protocols for privacy-preserving set operations have considered semi-honest and malicious adversarial models in cryptographic settings, whereby an adversary is assumed to follow or arbitrarily deviate from the protocol. Semi-honest model provides weak security requiring small amount of computation, on the other hand, malicious model provides strong security requiring expensive computations like homomorphic encryption. However, efficient computation of such set operations are desirable for practical implementations. In this paper, we build efficient and private set operations avoiding the use of expensive tools like homomorphic encryption, zero knowledge proof, and oblivious transfer. Our protocol is constructed in game-theoretic model. In other words, instead of being semi-honest or malicious, the parties are viewed as rational and are assumed (only) to act in their self-interest. We show that our protocol satisfies computational Nash equilibrium.
M. Sowmyavarshini, D. Palanikkumar, Gunjan Rathi
Cloud computing dynamically provides high quality cloudbased secure services and applications over the internet. The efficient sharing of secure cloud storage services (ESC) scheme which allows the upper-level user to share the secure cloud storage services with multiple lower-level users. In hierarchical identity-based architecture, the sender needs to encrypt a file only once and store only one copy of the corresponding ciphertext in a cloud. The lower-level user needs to decrypt a file which will increase the computational overhead, because the lower-level user does not perform any partial decipherment. In this paper, we propose a Trapdoor commitment scheme that enables a lower-level user to send a short trapdoor to the cloud service provider before retrieving files. This scheme allows the CSP to participate in the partial decipherment, so as to reduce computational overhead on the users without leaking any information about the plaintext. If a lower-level user wants to retrieve a file with limited bandwidth, CPU and memory, the trapdoor which will largely helps to reduce computational power.
Björn Terelius, Douglas Wikström
No abstract is available for this record.
George Drosatos, Αιμιλία Τασίδου, Pavlos S. Efraimidis
No abstract is available for this record.
Prabhanjan Ananth, Raghav Bhaskar, Vipul Goyal, Vanishree Rao
The Fiat-Shamir paradigm was proposed as a way to remove interaction from 3-round proof of knowledge protocols and derive secure signature schemes. This generic transformation leads to very efficient schemes and has thus grown quite popular. However, this transformation is proven secure only in the random oracle model. In FOCS 2003, Goldwasser and Kalai showed that this transformation is provably insecure in the standard model by presenting a counterexample of a 3-round protocol, the Fiat-Shamir transformation of which is (although provably secure in the random oracle model) insecure in the standard model, thus showing that the random oracle is uninstantiable. In particular, for every hash function that is used to replace the random oracle, the resulting signature scheme is existentially forgeable. This result was shown by relying on the non-black-box techniques of Barak (FOCS 2001). An alternative to the Fiat-Shamir paradigm was proposed by Fischlin in Crypto 2005. Fischlin’s transformation can be applied to any so called 3-round “Fiat-Shamir proof of knowledge’ ’ and can be used to derive non-interactive zero-knowledge proofs of knowledge as well as signature schemes. An attractive property of this transformation is that it provides online extractability (i.e., the extractor works without having to rewind the prover). Fischlin remarks that in comparison to the Fiat-Shamir transformation, his construction tries to
Bo Zhang, Fangguo Zhang
Abstract. Similarity coefficients play an important role in many application aspects. Recently, a privacy-preserving similarity coefficients protocol for binary data was proposed by Wong and Kim (Computers and Mathematics with Application 2012). In this paper, we show that their protocol is not secure, even in the semi-honest model, since the client can retrieve the input of the server without deviating from the protocol. Also we propose a secure similarity coefficients computation in the presence of malicious adversaries, and prove it using the standard simulation-based security definitions for secure two-party computation. We also discuss several extensions of our protocol for settling other problems. Technical tools in our protocol include zero-knowledge proofs and distributed ElGamal encryption.
George Danezis, Markulf Kohlweiss, Benjamin Livshits, Alfredo Rial
Abstract. Nowadays, service providers gather fine-grained data about users to deliver personalized services, for example, through the use of third-party cookies or social network profiles. This poses a threat both to privacy, since the amount of information obtained is excessive for the purpose of customization, and authenticity, because those methods employed to gather data can be blocked and fooled. In this paper we propose privacy-preserving profiling techniques, in which users perform the profiling task locally, reveal to service providers the result and prove its correctness. We address how our approach applies to tasks of both classification and pattern recognition. For the former, we describe client-side profiling based on random forests, where users, based on certified input data representing their activity, resolve a random forest and reveal the classification result to service providers. For the latter, we show how to match a stream of user activity to a regular expression, or how to assign it a probability using a hidden Markov model. Our techniques, based on the use of zero-knowledge proofs, can be composed with other protocols as part of the certification of a larger computation. 1
Chao Li, Zheng Yuan, Ming Mao
No abstract is available for this record.
Amang Sudarsono, Toru Nakanishi, Nobuo Funabiki
To enhance user privacy, anonymous credential systems allow the user to convince a verifier of the possession of a certificate issued by the issuing authority anonymously. The typical application is the privacy-enhancing electronic ID (eID). Although a previously proposed system achieves the constant complexity in the number of finite-set attributes of the user, it requires the use of RSA. In this paper, we propose a pairing-based anonymous credential system excluding RSA that achieves the constant complexity. The key idea of our proposal is the adoption of a pairing-based accumulator that outputs a constant-size value from a large set of input values. Using zero-knowledge proofs of pairing-based certificates and accumulators, any AND and OR relation can be proved with the constant complexity in the number of finite-set attributes. We implement the proposed system using the fast pairing library, compare the efficiency with the conventional systems, and show the practicality in a mobile eID application.
Melissa Chase, Ivan Visconti
No abstract is available for this record.
Jan Camenisch, Maria Dubovitskaya, Kristiyan Haralambiev
No abstract is available for this record.
Olivier Blazy, David Pointcheval, Damien Vergnaud
No abstract is available for this record.