Follow blockchain research across journals, conferences, and preprint repositories.
3,460 results · page 137 of 145
Orlenys López‐Pintado, Luciano García‐Bañuelos, Marlon Dumas, Ingo Weber
No abstract is available for this record.
Yehuda Lindell
No abstract is available for this record.
Andrew Sutton, Reza Samavi
No abstract is available for this record.
Madars Virza
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2017.
Iddo Bentov, Yan Ji, Fan Zhang, Yunqi Li · 8 authors
No abstract is available for this record.
Leonid Reyzin, Dmitry Meshkov, Alexander Chepurnoy, Sasha Ivanov
No abstract is available for this record.
Jonatan Bergquist
The purpose of this Master's thesis is to explore blockchain technology and smart contracts as a way of building privacy-sensitive applications. The main focus is on a medication plan containing prescriptions, built on a blockchain system of smart contracts. This is an example use case, but the results can be transferred to other ones where sensitive data is being shared and a proof of validity or authentication is needed. First the problem is presented, why medication plans are in need of digitalisation and why blockchain technology is a fitting technology for implementing such an application. Then blockchain technology is explained, since it is a very new and relatively unfamiliar IT construct. Thereafter, a design is proposed for solving the problem. A system of smart contracts was built to prove how such an application can be built, and suggested guidelines for how a blockchain system should be designed to fulfil the requirements that were defined. Finally, a discussion is held regarding the applicability of different blockchain designs to the problem of privacy-handling applications.
Pratyush Dikshit, Kunwar Singh
Bitcoin is a digital currency based on cryptographic algorithms. All the transactions of this currency are recorded and stored in a publically available database called blockchain. Since, these transactions are available to everyone, bitcoins must be stored in a secured wallet. These bitcoin wallets can be opened only by its secret key. And if once the secret key of the wallet is lost, it cannot be recovered because of the irreversible nature of bitcoin transaction. To root out this problem, Goldfeder et al. [4] proposed a solution of threshold signature scheme compatible with bitcoins signature by using Elliptic Curve Digital Signature Algorithm (ECDSA) providing security policy of shared control of a wallet in which each player gets only a single share. Considering an important point of priority/weightage of players, Dikshit and Singh [12] first proposed a scheme in which each player is given one or more shares of the secret key according to his weightage/priority. This scheme has a drawback of managing and handling many keys by each player. Suppose a player has weightage w, then he possesses w different shares of secret key. This problem is resolved in the proposed scheme in this paper. We propose a scheme in which all the players get single share and can accomplish the requirements of concept of weightage. We extend the weighted threshold ECDSA scheme in order to realize efficient weighted threshold ECDSA scheme.
Paweł Szewczyk
No abstract is available for this record.
Thanh Bui, Tuomas Aura
Blockchains and other public ledger structures promise a new way to create globally consistent event logs and other records. We make use of this consistency property to detect and prevent man-in-the-middle attacks in a key exchange such as Diffie-Hellman or ECDH. Essentially, the MitM attack creates an inconsistency in the world views of the two honest parties, and they can detect it with the help of the ledger. Thus, there is no need for prior knowledge or trusted third parties apart from the distributed ledger. To prevent impersonation attacks, we require user interaction. It appears that, in some applications, the required user interaction is reduced in comparison to other user-assisted key-exchange protocols.
Benedikt Bünz, Jonathan Bootle, Dan Boneh, Andrew Poelstra · 6 authors
We propose Bulletproofs, a new non-interactive zero-knowledge proof protocol with very short proofs and without a trusted setup; the proof size is only logarithmic in the witness size. Bulletproofs are especially well suited for efficient range proofs on committed values: they enable proving that a committed value is in a range using only 2 log_2(n)+9 group and field elements, where n is the bit length of the range. Proof generation and verification times are linear in n. Bulletproofs greatly improve on the linear (in n) sized range proofs in existing proposals for confidential transactions in Bitcoin and other cryptocurrencies. Moreover, Bulletproofs supports aggregation of range proofs, so that a party can prove that m commitments lie in a given range by providing only an additive O(log(m)) group elements over the length of a single proof. To aggregate proofs from multiple parties, we enable the parties to generate a single proof without revealing their inputs to each other via a simple multi-party computation (MPC) protocol for constructing Bulletproofs. This MPC protocol uses either a constant number of rounds and linear communication, or a logarithmic number of rounds and logarithmic communication. We show that verification time, while asymptotically linear, is very efficient in practice. The marginal cost of batch verifying 32 aggregated range proofs is less than the cost of verifying 32 ECDSA signatures. Bulletproofs build on the techniques of Bootle et al. (EUROCRYPT 2016). Beyond range proofs, Bulletproofs provide short zero-knowledge proofs for general arithmetic circuits while only relying on the discrete logarithm assumption and without requiring a trusted setup. We discuss many applications that would benefit from Bulletproofs, primarily in the area of cryptocurrencies. The efficiency of Bulletproofs is particularly well suited for the distributed and trustless nature of blockchains. The full version of this article is available on ePrint.
Russell O’Connor, Marta Piekarska
No abstract is available for this record.
Pyrros Chaidos, Geoffroy Couteau
We propose a framework for constructing efficient designated-verifier non-interactive zero-knowledge proofs (\(\mathsf {DVNIZK}\)) for a wide class of algebraic languages over abelian groups, under standard assumptions. The proofs obtained via our framework are proofs of knowledge, enjoy statistical, and unbounded soundness (the soundness holds even when the prover receives arbitrary feedbacks on previous proofs). Previously, no efficient \(\mathsf {DVNIZK}\) system satisfying any of those three properties was known. Our framework allows proving arbitrary relations between cryptographic primitives such as Pedersen commitments, ElGamal encryptions, or Paillier encryptions, in an efficient way. For the latter, we further exhibit the first non-interactive zero-knowledge proof system in the standard model that is more efficient than proofs obtained via the Fiat-Shamir transform, with still-meaningful security guarantees and under standard assumptions. Our framework has numerous applications, in particular for the design of efficient privacy-preserving non-interactive authentication.
Alexander Egberts
No abstract is available for this record.
Cristina Pérez‐Solà, Sergi Delgado-Segura, Guillermo Navarro‐Arribas, Jordi Herrera‐Joancomartí
Zero-confirmation transactions, i.e. transactions that have been broadcast but are still pending to be included in the blockchain, have gained attention in order to enable fast payments in Bitcoin, shortening the time for performing payments. Fast payments are desirable in certain scenarios, for instance, when buying in vending machines, fast food restaurants, or withdrawing from an ATM. Despite being quickly propagated through the network, zero-confirmation transactions are not protected against double-spending attacks, since the double-spending protection Bitcoin offers relies on the blockchain and, by definition, such transactions are not yet included in it. In this paper, we propose a double-spending prevention mechanism for Bitcoin zero-confirmation transactions. Our proposal is based on exploiting the flexibility of the Bitcoin scripting language together with a well-known vulnerability of the ECDSA signature scheme to discourage attackers from performing such an attack.
Ethan Cecchetti, Fan Zhang, Yan Ji, Ahmed E. Kosba · 6 authors
Blockchains and more general distributed ledgers are becoming increasingly popular as efficient, reliable, and persistent records of data and transactions. Unfortunately, they ensure reliability and correctness by making all data public, raising confidentiality concerns that eliminate many potential uses. In this paper we present Solidus, a protocol for confidential transactions on public blockchains, such as those required for asset transfers with on-chain settlement. Solidus operates in a framework based on real-world financial institutions: a modest number of banks each maintain a large number of user accounts. Within this framework, Solidus hides both transaction values and the transaction graph (i.e., the identities of transacting entities) while maintaining the public verifiability that makes blockchains so appealing. To achieve strong confidentiality of this kind, we introduce the concept of a Publicly-Verifiable Oblivious RAM Machine (PVORM). We present a set of formal security definitions for both PVORM and Solidus and show that our constructions are secure. Finally, we implement Solidus and present a set of benchmarks indicating that the system is efficient in practice.
Daniel E. O’Leary
Summary This paper investigates alternative configurations of different blockchain architectures that can be used for gathering and processing transactions in a range of different settings, including accounting, auditing, supply chain and other types of transaction information. Although there has been substantial focus on the peer‐to‐peer and public versions of blockchain, this paper focuses primarily on cloud‐based and private configuration versions of blockchains and investigates use configurations, advantages and limitations as firms bring blockchain‐based market mechanisms into their organizations. In addition, this paper investigates some emerging issues associated with blockchain use in consortium settings. Finally, this paper relates some proposed uses of blockchain for transaction processing to other technologies, such as data warehouses and databases.
Qi Xia, Emmanuel Boateng Sifah, Kwame Omono Asamoah, Jianbin Gao · 6 authors
The dissemination of patients' medical records results in diverse risks to patients' privacy as malicious activities on these records cause severe damage to the reputation, finances, and so on of all parties related directly or indirectly to the data. Current methods to effectively manage and protect medical records have been proved to be insufficient. In this paper, we propose MeDShare, a system that addresses the issue of medical data sharing among medical big data custodians in a trust-less environment. The system is blockchain-based and provides data provenance, auditing, and control for shared medical data in cloud repositories among big data entities. MeDShare monitors entities that access data for malicious use from a data custodian system. In MeDShare, data transitions and sharing from one entity to the other, along with all actions performed on the MeDShare system, are recorded in a tamper-proof manner. The design employs smart contracts and an access control mechanism to effectively track the behavior of the data and revoke access to offending entities on detection of violation of permissions on data. The performance of MeDShare is comparable to current cutting edge solutions to data sharing among cloud service providers. By implementing MeDShare, cloud service providers and other data guardians will be able to achieve data provenance and auditing while sharing medical data with entities such as research and medical institutions with minimal risk to data privacy.
Karl Wüst, Arthur Gervais
Blockchain is being praised as a technological innovation which allows to revolutionize how society trades and \ninteracts. This reputation is in particular attributable to its \nproperties of allowing mutually mistrusting entities to exchange \nfinancial value and interact without relying on a trusted third \nparty. A blockchain moreover provides an integrity protected \ndata storage and allows to provide process transparency. \nIn this paper we critically analyze whether a blockchain is \nindeed the appropriate technical solution for a particular application scenario. We differentiate between permissionless (e.g., \nBitcoin/Ethereum) and permissioned (e.g. Hyperledger/Corda) \nblockchains and contrast their properties to those of a centrally \nmanaged database. We provide a structured methodology to \ndetermine the appropriate technical solution to solve a particular \napplication problem. Given our methodology, we analyze in depth \nthree use cases — Supply Chain Management, Interbank and \nInternational Payments, and Decentralized Autonomous Organizations and conclude the article with an outlook for further \nopportunities.
Koteswara Rao Ballamudi
Distributed ledger technology (DLT) that stores data (usually immutable and sequenced transaction records) in a decentralized way through cryptography and consensus algorithms. The first widely recognized implementation of the blockchain took place in 2009 on the Bitcoin public blockchain. Since then, other types of blockchain have been developed for a wide range of applications and features built on common principles such as decentralization, encryption, consensus, and immutability. In particular, blockchain technology is most widely used in transaction settlement and digital currency banks and the financial sector, as well as in supply chain applications that help participants solve problems quickly and efficiently. Other use cases continue to be developed. As a form of information management, blockchain and related DLTs offer advantages over traditional databases and may help develop certain new technologies such as the Internet of Things. Blockchain regulation is currently restricted at the international and federal levels, but state-level legislation provides support and awareness of aspects of blockchain technology. Most of the current regulations are in the form of self-regulation by blockchain developers and related communities, but many challenges and risks such as data privacy and security need to be addressed in the near future.
G. Kalpana, P. V. Kumar, R. V. Krishnaiah
Cloud was visualized as the authentic elucidation for rising storage space and service expenditure for Information Technology Applications. Outsourcing the data to cloud storage servers ease the client accountability by facilitating stumpy cost, secure, locality independent platforms and scalable resources. With the proliferation of cloud technologies, outsourced data is scrolling among the nodes, client unaware of storage location and no longer have possession of data. Data privacy and integrity are formidable concerns for data owners. So, verification of data integrity is vital. Thus, an efficient auditing scheme is required to guarantee data possessor so as to assure them data safety and accuracy. In this paper, we propose zero knowledge proof interactive system for data integrity verification on cloud. Our method strengthened by using Homomorphic encryption tags, generated on encrypted data with zero knowledge to the interactive members. We consider TPA (Third Party Auditor) as audit agent inside the cloud on behalf of client to reduce the communication cost. The scheme drastically reduces input and output costs by generating the probabilistic proof of possession using sampling sets of data blocks from the server. Client maintains meta data of file for verification, which reduces huge communication cost on network. Our theoretical analysis and experimental results show the efficiency of the scheme for integrity proofs.
D. Ragav Prasanth, N SANDEEP, TALLURU CHAITANYA
Provable data possession (PDP) is a technique for ensuring the integrity of data in storage outsourcing. In this paper, we address the construction of an efficient PDP scheme for distributed cloud storage to support the scalability of service and data migration, in which we consider the existence of multiple cloud service providers to cooperatively store and maintain the clients' data. We present a cooperative PDP (CPDP) scheme based on homomorphic verifiable response and hash index hierarchy. We prove the security of our scheme based on multi-prover zero-knowledge proof system, which can satisfy completeness, knowledge soundness, and zero-knowledge properties. In addition, we also propose a fuzzy clustering system for analyzing the high dimensional Data bases in cloud Environments. This paper proposes novel effective fuzzy soft clustering systems with the combination of possibilistic c-means.
Lexus Jun Hong Sim, Shu Qin Ren, Sye Loong Keoh, Khin Mi Mi Aung
There is a significant increase in the amount of data breaches in corporate servers in the cloud environments. This includes username and password compromise in the cloud and account hijacking, thus leading to severe vulnerabilities of the cloud service provisioning. Traditional authentication schemes rely on the users to use their credentials to gain access to cloud service. However once the credential is compromised, the attacker will gain access to the cloud service easily. This paper proposes a novel scheme that does not require the user to present his credentials, and yet is able to prove ownership of access to the cloud service using a variant of zero-knowledge proof. A challenge-response protocol is devised to authenticate the user, requiring the user to compute a one-time pad (OTP) to authenticate himself to the server without revealing password to the server. A prototype has been implemented to facilitate the authentication of the user when accessing Dropbox, and the experiment results showed that the overhead incurred is insignificant.
Jörn Erbguth, Jean‐Henry Morin
Digital traces play an increasingly important role in our society. Whether in the context of regulatory compliance, contractual exchanges or simply for general interactions, people need to be able to document trustworthy facts. Most approaches today rely either on Trusted Third Parties, at best, or more generally on collecting such traces after problems occur in ways where their authenticity may be arguable (fabricated, doctored). Blockchain technology offers an interesting alternative to the problem by allowing documenting transactions in a distributed consensus ledger with transparency and immutability properties. This paper proposes a new approach to the problem leveraging blockchain technology towards providing a framework for distributed trustworthy logging of digital facts and traces on the blockchain as they happen or are needed before problems arise. Disintermediation of such processes is likely to significantly help raise trust and accountability in many aspects of our interactions, whether online or offline.