Follow blockchain research across journals, conferences, and preprint repositories.
4,146 results · page 108 of 173
Yuyu Wang, Jiaxin Pan, Yu Chen
No abstract is available for this record.
Silvio Šimunić, Dalen Bernaca, Kristijan Lenac
From weak clients outsourcing computational tasks to more powerful machines, to distributed blockchain nodes needing to agree on the state of the ledger in the presence of adversarial nodes, there is a growing need to efficiently verify the results of computations delegated to untrusted third parties. Verifiable computing is a new and interesting research area that addresses this problem. Recently, new applications of verifiable computing techniques have emerged in blockchain technology for secure key management, sybil-resistance and distributed consensus, and smart contracts, while providing desired performance and privacy guarantees. In this paper, we provide an overview of common methods for verifying computation and present how they are applied to blockchain technology. We group the presented verifiable computing applications into five main application areas, i.e., multiparty approval for secure key management, sybil-resistance and consensus, smart contracts and oracles, scalability, and privacy. The main contribution of this survey is to answer two research questions: 1) what are the main application areas of verifiable computing in blockchain technology, and 2) how are verifiable computing techniques used in major blockchain projects today.
Alaa Omran Almagrabi, Ali Kashif Bashir
The design of distributed ledger, Asymmetric Key Algorithm (AKA) blockchain systems, is prominent in administering security and access control in various real-time services and applications. The assimilation of blockchain systems leverages the reliable access and secure service provisioning of the services. However, the distributed ledger technology’s access control and chained decisions are defaced by pervasive and service unawareness. It results in degrading security through unattended access control for limited-service users. In this article, a service-aware access control procedure (SACP) is introduced to address the afore-mentioned issue. The proposed SACP defines attended access control for all the service session by identifying the users and service provider availability. The distributed nature of the ledger systems and classification tree learning are combined to determine unattended access. The sole access is determined by summarizing the closed and open access requests and the service provider’s availability and integrity checks. In this process, the learning process classifies the secured access request and completed the integrity checks of the current and previous service dissemination. This classification-based access administration reduces the service disconnections and false access rate of the applications.
Efe Seyitoglu, Attila A. Yavuz, Thang Hoang
Proof-of-Work (PoW) is one of the fundamental and widely-used consensus algorithms in blockchains. In PoW, nodes compete to receive the mining reward by trying to be the first to solve a puzzle. Despite its fairness and wide-availability, traditional PoW incurs extreme computational and energy waste over the blockchain. This waste is considered to be one of the biggest problems in PoW-based blockchains and cryptocurrencies. In this work, we propose a new useful PoW called Proof-of-Useful-Randomness (PoUR) that mitigates the energy waste by incorporating pre-computed (disclosable) randomness into the PoW. The key idea is to inject special randomness into puzzles via algebraic commitments that can be stored and later disclosed. Unlike the traditional wasteful PoWs, our approach enables pre-computed commitments to be utilized by a vast array of public-key cryptography methods that require offline-online processing (e.g., digital signature, key exchange, zero-knowledge protocol). Moreover, our PoW preserves the desirable properties of the traditional PoW and therefore does not require a substantial alteration in the underlying protocol. We showed the security of our PoW, and then fully implemented it to validate its significant energy-saving capabilities.
Zhiyuan Xue, Miao Wang, Qiuyue Zhang, Yunfeng Zhang · 5 authors
Blockchain is a decentralized distributed ledger technology. The public chain represented by Bitcoin and Ethereum only realizes the limited anonymity of user identity, and the transaction amount is open to the whole network, resulting in user privacy leakage. Based on the existing anonymous technology, the concealment of the sender, receiver, amount of the transaction, and does not disclose any information, which makes the supervision difficult. Therefore, the design of blockchain scheme with privacy protection and supervision functions is of great significance. In this paper, a blockchain transaction model with both privacy and supervision function is proposed. It uses probability encryption to realize the hiding of the true identity of the blockchain transaction, and uses the commitment scheme and zero-knowledge proof technology to realize the privacy protection and guarantee legitimacy verification of the transaction. With the use of encryption technology, the regulators can supervise blockchain transactions without storing the users' information, which greatly reduces the pressure on storage, computing and key management. In addition, it does not rely on specific consensus mechanism and can be used as an independent module. The security performance analysis shows that the proposed scheme has great practicability and has potential application in many fields.
Amir Kafshdar Goharshady
Suppose that Alice plans to buy a physical good from Bob over a programmable Blockchain. Alice does not trust Bob, so she is not willing to pay before the good is delivered off-chain. Similarly, Bob does not trust Alice, so he is not willing to deliver the good before getting paid on-chain. Moreover, they are not inclined to use the services of a trusted third-party. Traditionally, such scenarios are handled by game-theoretic escrow smart contracts, such as BitHalo. In this work, we first show that the common method for this problem suffers from a major flaw which can be exploited by Bob in order to extort Alice. We also show that, unlike the case of auctions, this flaw cannot be addressed by a commitment-scheme-based approach. We then provide a much more general result: assuming that the two sides are rational actors and the smart contract language is Turing-complete, there is no escrow smart contract that can facilitate this exchange without either relying on third parties or enabling at least one side to extort the other.∗∗A preprint of this work appeared in [1].
Jiacheng Liang, Songze Li, Cao, Bochuan, Wensi Jiang · 5 authors
We propose OmniLytics, a blockchain-based secure data trading marketplace for machine learning applications. Utilizing OmniLytics, many distributed data owners can contribute their private data to collectively train an ML model requested by some model owners, and receive compensation for data contribution. OmniLytics enables such model training while simultaneously providing 1) model security against curious data owners; 2) data security against the curious model and data owners; 3) resilience to malicious data owners who provide faulty results to poison model training; and 4) resilience to malicious model owners who intend to evade payment. OmniLytics is implemented as a blockchain smart contract to guarantee the atomicity of payment. In OmniLytics, a model owner splits its model into the private and public parts and publishes the public part on the contract. Through the execution of the contract, the participating data owners securely aggregate their locally trained models to update the model owner's public model and receive reimbursement through the contract. We implement a working prototype of OmniLytics on Ethereum blockchain and perform extensive experiments to measure its gas cost, execution time, and model quality under various parameter combinations. For training a CNN on the MNIST dataset, the MO is able to boost its model accuracy from 62% to 83% within 500ms in blockchain processing time.This demonstrates the effectiveness of OmniLytics for practical deployment.
Ignacio Amores-Sesar, Christian Cachin, Anna Parker
Despite the tremendous interest in cryptocurrencies like Bitcoin and Ethereum today, many aspects of the underlying consensus protocols are poorly understood. Therefore, the search for protocols that improve either throughput or security (or both) continues. Bitcoin always selects the longest chain (i.e., the one with most work). Forks may occur when two miners extend the same block simultaneously, and the frequency of forks depends on how fast blocks are propagated in the network. In the GHOST protocol, used by Ethereum, all blocks involved in the fork contribute to the security. However, the greedy chain selection rule of GHOST does not consider the full information available in the block tree, which has led to some concerns about its security. This paper introduces a new family of protocols, called Medium, which takes the structure of the whole block tree into account, by weighting blocks differently according to their depths. Bitcoin and GHOST result as special cases. This protocol leads to new insights about the security of Bitcoin and GHOST and paves the way for developing network- and application-specific protocols, in which the influence of forks on the chain-selection process can be controlled. It is shown that almost all protocols in this family achieve strictly greater throughput than Bitcoin (at the same security level) and resist attacks that can be mounted against GHOST.
Songlin He, Yuan Lu, Qiang Tang, Guiling Wang · 5 authors
Peer-to-peer (p2p) content delivery is promising to provide benefits like cost-saving and scalable peak-demand handling in comparison with conventional content delivery networks (CDNs) and complement the decentralized storage networks such as Filecoin. However, reliable p2p delivery requires proper enforcement of delivery fairness, i.e., the deliverers should be rewarded according to their in-time delivery. Unfortunately, most existing studies on delivery fairness are based on non-cooperative game-theoretic assumptions that are arguably unrealistic in the ad-hoc p2p setting. We for the first time put forth the expressive yet still minimalist securities for p2p content delivery, and give two efficient solutions FairDownload and FairStream via the blockchain for p2p downloading and p2p streaming scenarios, respectively. Our designs not only guarantee delivery fairness to ensure deliverers be paid (nearly) proportional to his in-time delivery, but also ensure the content consumers and content providers to be fairly treated. The fairness of each party can be guaranteed when the other two parties collude to arbitrarily misbehave. Moreover, the systems are efficient in the sense of attaining asymptotically optimal on-chain costs and optimal deliverer communication. We implement the protocols to build the prototype systems atop the Ethereum Ropsten network. Extensive experiments done in LAN and WAN settings showcase their high practicality.
Victor von Wachter, Johannes Rude Jensen, Omri Ross
Decentralized financial (DeFi) applications on the Ethereum blockchain are highly interoperable because they share a single state in a deterministic computational environment. Stakeholders can deposit claims on assets, referred to as 'liquidity shares', across applications producing effects equivalent to rehypothecation in traditional financial systems. We seek to understand the degree to which this practice may contribute to financial integration on Ethereum by examining transactions in 'composed' derivatives for the assets DAI, USDC, USDT, ETH and tokenized BTC for the full set of 344.8 million Ethereum transactions computed in 2020. We identify a salient trend for 'composing' assets in multiple sequential generations of derivatives and comment on potential systemic implications for the Ethereum network.
Benjamin Körbel, Marten Sigwart, Philip Frauenthaler, Michael Sober · 5 authors
Offloading of computation, e.g., to the cloud, is today a major task in distributed systems. Usually, consumers which apply offloading have to trust that a particular functionality offered by a service provider is delivering correct results. While redundancy (i.e., offloading a task to more than one service provider) or (partial) reprocessing help to identify correct results, they also lead to significantly higher cost. Hence, within this paper, we present an approach to verify the results of offchain computations via the blockchain. For this, we apply zero-knowledge proofs to provide evidence that results are correct. Using our approach, it is possible to establish trust between a service consumer and arbitrary service providers. We evaluate our approach using a very well-known example task, i.e., the Traveling Salesman Problem.
Lorenzo Andolfo, Luigi Coppolino, Salvatore D’Antonio, Giovanni Mazzeo · 8 authors
The majority of financial organizations managing confidential data are aware of security threats and leverage widely accepted solutions (e.g., storage encryption, transport-level encryption, intrusion detection systems) to prevent or detect attacks. Yet these hardening measures do little to face even worse threats posed on data-in-use. Solutions such as Homomorphic Encryption (HE) and hardware-assisted Trusted Execution Environment (TEE) are nowadays among the preferred approaches for mitigating this type of threat. However, given the high-performance overhead of HE, financial institutions -- whose processing rate requirements are stringent -- are more oriented towards TEE-based solutions. The X-Margin Inc. company, for example, offers secure financial computations by combining the Intel SGX TEE technology and HE-based Zero-Knowledge Proofs, which shield customers' data-in-use even against malicious insiders, i.e., users having privileged access to the system. Despite such a solution offers strong security guarantees, it is constrained by having to trust Intel and by the SGX hardware extension availability. In this paper, we evaluate a new frontier for X-Margin, i.e., performing privacy-preserving credit risk scoring via an emerging cryptographic scheme: Functional Encryption (FE), which allows a user to only learn a function of the encrypted data. We describe how the X-Margin application can benefit from this innovative approach and -- most importantly -- evaluate its performance impact.
Jonathan Heiss, Anselm Busse, Stefan Tai
Prior to provisioning sensor data to smart contracts, a pre-processing of the data on intermediate off-chain nodes is often necessary. When doing so, originally constructed cryptographic signatures cannot be verified on-chain anymore. This exposes an opportunity for undetected manipulation and presents a problem for applications in the Internet of Things where trustworthy sensor data is required on-chain. In this paper, we propose trustworthy pre-processing as enabler for end-to-end sensor data integrity in data on-chaining workflows. We define requirements for trustworthy pre-processing, present a model and common workflow for data on-chaining, select off-chain computation utilizing Zero-knowledge Proofs (ZKPs) and Trusted Execution Environments (TEEs) as promising solution approaches, and discuss both our proof-of-concept implementations and initial experimental, comparative evaluation results. The importance of trustworthy pre-processing and principle solution approaches are presented, addressing the major problem of end-to-end sensor data integrity in blockchain-based IoT applications.
Vincenzo Botta, Daniele Friolo, Daniele Venturi, Ivan Visconti
In this work, we consider executions of smart contracts for implementing secure multi-party computation (MPC) protocols on forking blockchains (e.g., Ethereum), and we study security and delay issues due to forks. In this setting, the classical double-spending problem tells us that messages of the MPC protocol should be confirmed on-chain before playing the next ones, thus slowing down the entire execution. Our contributions are twofold: For the concrete case of fairly tossing multiple coins with penalties, we notice that the lottery protocol of Andrychowicz et al. (S&P ’14) becomes insecure if players do not wait for the confirmations of several transactions. In addition, we present a smart contract that instead retains security even when all honest players immediately answer to transactions appearing on-chain. We analyze the performance using Ethereum as testbed.We design a compiler that takes any “digital and universally composable” MPC protocol (with or without honest majority), and transforms it into another one (for the same task and same setup) which maintains security even if all messages are played on-chain without delays. The special requirements on the starting protocol mean that messages consist only of bits (e.g., no hardware token is sent) and security holds also in the presence of other protocols. We further show that our compiler satisfies fairness with penalties as long as honest players only wait for confirmations once. By reducing the number of confirmations, our protocols can be significantly faster than natural constructions.
Suthee Ruangwises
Sudoku is a famous logic puzzle where the player has to fill a number between 1 and 9 into each empty cell of a $9 \times 9$ grid such that every number appears exactly once in each row, each column, and each $3 \times 3$ block. In 2020, Sasaki et al. developed a physical card-based protocol of zero-knowledge proof (ZKP) for Sudoku, which enables a prover to convince a verifier that he/she knows a solution of the puzzle without revealing it. Their protocol uses 90 cards, but requires nine identical copies of some cards, which cannot be found in a standard deck of playing cards (consisting of 52 different cards and two jokers). Hence, nine identical standard decks are required to perform that protocol, making the protocol not very practical. In this paper, we propose a new ZKP protocol for Sudoku that can be performed using only two standard decks of playing cards, regardless of whether the two decks are identical or different. In general, we also develop the first ZKP protocol for a generalized $n \times n$ Sudoku that can be performed using a deck of all different cards.
Baobao Chai, Biwei Yan, Anming Dong, Jiguo Yu
With the development of Internet of things, more and more objects are connected to the Internet. It will lead to data leakage caused by arbitrary access easily. Thus, an effective method to prevent data leakage is needed. Traditional access control schemes include role-based access control (RBAC), attribute-based access control (ABAC), and capability-based access control (CapBAC) are all using a central or a third trusted party to manage user information, which is prone to single failure. In order to solve the problems, in this paper, a fine-grained access control scheme based on blockchain technology named SFAC is proposed. In recent years, blockchain technology has been widely studied and applied in various fields. It has the advantages of decentralization, imitation tampering, and traceability, and is a distributed public ledger. Therefore, combined with blockchain, SFAC can not only solve the problem of centralization, but also allow users to request resources in batches, and uses token mechanism to facilitate users’ requests. After the user gets a token, it can directly use the token to revoke resources. Besides, we use a smart contract to implement our proposed scheme and carrying out a series of experiments on the test network of Ethereum. The experimental results show that our SAFC is feasible.
Yang Yang, Zhangshuang Guan, Zhiguo Wan, Jian Weng · 6 authors
Election and voting play crucial roles in democratic society for an elactorate to make a collective decision. E-voting is one of the most challenging problems in cryptographic research to provide multiple dimensions security assurances. In this paper, we study an important voting paradigm, score voting, with privacy protection, which has not been investigated in previous work. We propose a blockchain based self-tallying election system to support score voting, dubbed “PriScore”, where the ballots are recorded on blockchain to prevent vote forgery or tampering. PriScore makes it possible for each voter to assign different evaluation scores (within a certain range) for the candidates as ranked-choice, where the sum of the scores in each ballot should be a predefined constant, and the evaluation scores are encrypted to maintain confidentiality. A major challenge in score voting is to simultaneously prove two constraint conditions: range proof and sum proof. We introduce a new technique, called dual zero-knowledge proof (dual-ZKP), to prove the scores satisfying two crucial requirements, which integrates “1-out-of-$K$” proof and distributed ElGamal crypto in a non-trivial way. The self-tallying mechanism in PriScore enables any party in the system to calculate and verify the election result, which provides fairness, dispute-freeness. The security analysis demonstrates that PriScore achieves completeness, soundness, eligibility, universal/individual verifiability and multiple-voting detection. We evaluate the performance of PriScore on modern workbench to test the performance, and also on a blockchain platform to measure the resource consumption. The experiments show that PriScore preserves privacy of score voting with reasonable overheads.
Cathrine Paulsen
Hyperledger Fabric is a permissioned enterprise blockchain allowing organizations to collaborate and automate processes via smart contracts. However, these contracts could contain security vulnerabilities leading to unexpected behavior or other negative consequences. Therefore, this study takes a closer look at three reported smart contract vulnerabilities in Fabric: rich queries, pseudorandom number generators, and global variables. Smart contracts containing these vulnerabilities were deployed on a test network, and the vulnerable contract features were exploited and explained. The study provides an estimation of each vulnerability's impact severity, and possible countermeasures to lower it were explored and evaluated. This study found that the proposed countermeasures can at least mitigate the impact severity of all three vulnerabilities.<br/>Additionally, the study provides an overview of compatible analysis tools. The available tools were found to be lacking, however, as most of them do not exist outside of research papers. Overall, static code analysis tools were found to be effective at detecting all three vulnerabilities.
Ibrahim Tariq Javed, Fares Alharbi, Tiziana Margaria, Noël Crespi · 5 authors
With the increasing use of smart devices and sensors, enormous amounts of data are being generated continuously. The data is commonly stored in centralized cloud platforms and consumed by different services. The data is indeed a valuable resource for many service providers who provide advanced features and utilities to their subscribers. However, user data include personal and sensitive information which can be misused in many ways. There is no way for a subscriber to confirm that their service provider is compliant with data privacy regulations. The existing privacy enhancing techniques such as anonymization and differential privacy substantially reduce data usability while ensuring privacy. Therefore, it remains essential to provide a feasible solution that allows service providers to take advantage of user data while guaranteeing their privacy. In this paper, we present PETchain: a novel privacy enhancing technology using blockchain and smartcontract. In PETchain, data is stored securely in a distributed manner and processed in a user-selected trusted execution environment. Users deploy the smartcontract that allows them to decide whether and how their data can be exploited by service providers. The feasibility and performance of PETchain are presented by implementing PETchain over a consortium Ethereum blockchain.
Gyeong-Jin Ra, Taehoon Kim, Im-Yeong Lee
The human internet of things (HIoT) is a promising trend that adopts a user-centered vision to improve life quality by interacting with heterogeneous physical and virtual entities and the internet. However, It refers to exchanging contextual data between collaborative entities that raise privacy concerns. Emerging blockchain technology allows a digital identity management system (IDM) to be deployed in it, which largely alleviates the problems caused by the centralized third party. Still, its inherent transparency and lack of privacy pose a considerable challenge to IDM. We propose verifiable anonymous identity management (VAIM) connecting privacy channels between users by constructing identity verification and access control provisioning via user-centric decisions and an anonymous identity management system. This work has the following contributions: (1) We establish a novel IDM system by analyzing the existing scheme. In this regard, we improve the traditional claim identity model in blockchain by implementing zero-knowledge proof (ZKP) algorithms to achieve identity unlinkability, essentially preventing the disclosure of attribute ownership. (2) We implement a system that includes blind ordered multi-signature (BOMS) protocol, which allows users to processes efficiently and trusts the verification of anonymous transactions. (3) Finally, specific ZKP-based algorithm (commonly used practical ZKP such as Camenisch and Lysyanskaya signature (CL-Signature) and zero-knowledge succinct non-interactive argument of knowledge (ZK-SANRKS)) implementation and various environment performance evaluation and security analysis show that our scheme achieves efficient privacy protection and a broader application scope compared with the prior model. To the best of our knowledge, existing zero-knowledge proof-based IDM has not developed or compared each scheme before.
Rafael Torres Moreno, Jesús García-Rodríguez, Jorge Bernal Bernabé, Antonio Skármeta
Identity Management (IdM) systems have traditionally relied on a centralized model prone to privacy, trust, and security problems, like potential massive data breaches or identity spoofing. Identity providers accumulate excessive power that might allow them to become a big brother, analyzing and storing as much data as possible. Users should be able to trust identity providers and manage their personal information straightforwardly without compromising their privacy. The European OLYMPUS project introduces a distributed approach for IdM based on enhanced Attribute-Based Credentials (ABC) that splits the role of Identity Provider to limit their influence and chances to become a unique point of failure. However, the trust relationship between service providers, users, and identity providers is still a gap in those kinds of privacy-preserving ABC systems. Decentralized technologies are an opportunity to break away from the centralized model and propose systems that respect privacy while increasing users' trust. This paper presents an evolution of the OLYMPUS architecture, maintaining all the privacy features and incorporating distributed ledger technologies to enhance trust and security in online transactions and IdM systems. The proposed system has been implemented, tested, and validated, showing its performance and feasibility to manage user's identity in a fully privacy-preserving, distributed and reliable way.
Thomas Haines, Johannes Müller
No abstract is available for this record.
Lydia Negka, Γεώργιος Σπαθούλας
Blockchain technology has been quite popular during recent years and it finally seems to present a significant rise with respect to its use for real-world applications. This advancement has brought up a critical challenge that public blockchain systems face, which is scalability. Most of the currently deployed systems fail to cope with increasing usage. In order to provide the promised security guarantees, large delays and high usage fees are imposed for submitted transactions and thus widespread adoption of the technology is hindered. A number of different approaches have been proposed to increase the capacity of blockchain systems with respect to processing transactions. The present survey focuses on one of the most popular ones, that of state channels, and to the extent of our knowledge constitutes the first collective survey of research in this field. An extensive analysis of relevant publications is conducted and a general view on the domain is provided. We have identified the limitations discussed through all relevant research efforts along with the various features that differentiate proposed designs. A comparison between retrieved papers is carried out on the basis of those limitations and features. Finally, future research directions are analysed while the role of state channels in the general public blockchain ecosystem is also discussed.
M. Albrecht, Alex Davidson, Amit Deo, Nigel P. Smart
No abstract is available for this record.