With the rapid advancement of cloud computing, cloud storage services have developed rapidly. One issue that has attracted particular attention in such remote storage services is that cloud storage servers are not enough to reliably save and maintain data, which greatly affects users’ confidence in purchasing and consuming cloud storage services. Traditional data integrity auditing techniques for cloud data storage are centralized, which faces huge security risks due to single-point-of-failure and vulnerabilities of central auditing servers. Blockchain technology offers a new approach to this problem. Many researchers have endeavored to employ the blockchain for data integrity auditing. Based on the search of relevant papers, we found that existing literature lacks a thorough survey of blockchain-based integrity auditing for cloud data. In this paper, we make an in-depth survey on cloud data integrity auditing based on blockchain. Firstly, we cover essential basic knowledge of integrity auditing for cloud data and blockchain techniques. Then, we propose a series of requirements for evaluating existing Blockchain-based Data Integrity Auditing (BDIA) schemes. Furthermore, we provide a comprehensive review of existing BDIA schemes and evaluate them based on our proposed criteria. Finally, according to our completed review and analysis, we explore some open issues and suggest research directions worthy of further efforts in the future.
Whereas the use of distributed ledger technologies has previously been limited to cryptocurrencies, other sectors—such as healthcare, supply chain, and finance—can now benefit from them because of bitcoin scripts and smart contracts. However, these applications rely on oracles to fetch data from the real world, which cannot reproduce the trustless environment provided by blockchain networks. Despite their crucial role, academic research on blockchain oracles is still in its infancy, with few contributions and a heterogeneous approach. This study undertakes a bibliometric analysis by highlighting institutions and authors that are actively contributing to the oracle literature. Investigating blockchain oracle research state of the art, research themes, research directions, and converging studies will also be highlighted to discuss, on the one hand, current advancements in the field and, on the other hand, areas that require more investigation. The results also show that although worldwide collaboration is still lacking, various authors and institutions have been working in similar directions.
Catarina Pedreira, Rafael Belchior, Miguel Matos, André Vasconcelos
Blockchains currently exist in silos, competing when they could be cooperating. Interoperability is essential to allow for communication between them and motivate mass adoption. In permissioned blockchains, interoperability is harder given their opaqueness. The solutions proposed so far to address interoperability require a trusted private third party, which may be insecure and is not ideal. We propose T-ODAP, a secure multi-layered protocol that enables a trustless solution for permissioned blockchain interoperability, eliminating the need for trust in the protocol’s participants. It provides a Decentralized View Storage, a connector that connects permissioned blockchains to the latter, and a trustless version of the ODAP protocol. T-ODAP models the participants as rational agents using game theory techniques and is implemented using \textit{Polkadot} and \textit{Hyperledger Cactus}. We tested the implemented solution, evaluated the system’s robustness in face of attacks, and concluded that the system is \textit{(k,t)-weak-robust}.
Michael Bartholic, Áron Lászka, Go Yamamoto, Eric Burger
Blockchains benefit from guarantees of immutability and reliability due to their high redundancy and distributed nature. They show their value especially when operating between untrusted parties. Their functionality can be extended program-matically by smart contracts, but are limited by high costs of on-chain computation and only being able to truly trust data which is directly included on-chain. To attempt to bridge this limitation, blockchain oracles are introduced as a conceptual solution to act as a trusted source of information within the blockchain. The Oracle Problem emerges as we consider how one can introduce trusted information into a trust-free environment without compromising the validity of the blockchain. Many promising designs for oracle mechanisms have been proposed, but it is not readily apparent how one should assess the applicability of a given mechanism, nor the strengths and features between mechanisms. To be equipped to assess and categorize oracles, we must consider not just the possible answers, but the questions to which these oracles are trying to speak. Categorizing questions by their possible answering populations, we propose a framework for considering oracle questions and the context with which they are posed. We observe that there are limitations to what an oracle can hope to achieve, depending on the nature of the question, while noting the context in which a question exists can change what is viewed as true.
Rodrigo Dutra Garcia, Gowri Ramachandran, Raja Jurdak, Jó Ueyama
Real-world applications in healthcare and supply chain domains produce, exchange, and share data in a multi-stakeholder environment. Data owners want to control their data and privacy in such settings. On the other hand, data consumers demand methods to understand when, how, and who produced the data. These requirements necessitate data governance frameworks that guarantee data provenance, privacy protection, and consent management. We introduce a decentralized data governance framework based on blockchain technology and proxy re-encryption to let data owners control and track their data through privacy-enhancing and consent management mechanisms. Besides, our framework allows the data consumers to understand data lineage through a blockchain-based provenance mechanism. We have used Digital e-prescription as the use case since it has multiple stakeholders and sensitive data while enabling the medical fraternity to manage patients’ prescription data, involving patients as data owners, doctors, and pharmacists as data consumers. Our proof-of-concept implementation and evaluation results based on CosmWasm and pyUmbral PRE show that the proposed decentralized system guarantees transparency, privacy, and trust with minimal overhead.
Blockchain has been relevant in the document management process, serving as a storage solution with the potential to guarantee the relevant requirements needed for any document storage and validation solution. However, due to the distributed nature of blockchain, we may face implementation difficulties and high operational costs, for example. To facilitate this process, we propose a customizable blockchain-based document registration service that makes it possible to create different types of gen-eralized documents for various application domains and store them in one or more blockchains integrated in an Application Programming Interface (API).
Contracts established on a blockchain remove the need for intermediary third parties, but usually require external data to decide on an outcome, provided by a so-called oracle. Discreet Log Contracts were proposed as a way to establish such contracts on the Bitcoin blockchain without requiring interaction with an oracle, increasing the privacy of the contracting parties. To enable cross-compatible implementations to be developed, a specification effort was carried out, that led to various improvements over and additions to the original proposal. In particular, we present in this paper a simpler protocol making use of adaptor signatures, detail the handling of contracts with numerical outcomes, and how to create them using multiple oracles. We also provide some algorithmic optimizations to speed up contract creation and experimental results on performance highlighting their impact and demonstrating the useability of the overall system.
With the recent advance in concepts like decentralized "cloud" and blockchain-enabled decentralized computing environments, the legacy modeling and orchestration tools developed to support centrally managed cloud-based ICT infrastructures are challenged by such a new paradigm built on top of decentralization. On the other hand, decentralized "cloud" and computing infrastructures need to support many Dapp use cases. As the complexity of these targeted application scenarios increases, there is an urgent need for developing automation and modeling tools for deploying and managing decentralized infrastructures. Instead of creating such tools from scratch, a natural approach is extending mature infrastructure modeling tools for Dapps and decentralized computing environments. To this end, in this work, we have developed extensions to the TOSCA domain-specific language to support smart contract specification of decentralized computing infrastructures for supporting Dapps, where smart contracts or chain codes manage a decentralized computing environment. The result is blockchain-based orchestration and automation for decentralized "cloud" and computing environments, which is a step forward for achieving full decentralization in general-purpose computing.
Blockchain technology is one of the most popular information technologies at present, and its security features are realized through various cryptographic tools. Zero-knowledge proofs are such a tool that can increase data security and improve users’ privacy, and zero-knowledge proof schemes constructed with polynomial commitments have advantages in terms of verification time and proof size. Benefiting from the development of blockchain technology, zero-knowledge proof has also ushered in rapid development. This paper analyzes the research status of zero-knowledge proof schemes based on polynomial commitment construction, and introduces the construction and security of polynomial commitments. Finally, blockchain and some other potential commitment schemes that can be used for zero-knowledge proofs and blockchain construction are introduced as future research directions and engineering applications.
Digital signature schemes are a fundamental component of secure distributed systems, and the theft of a signing-key might have huge real-world repercussions e.g., in applications such as cryptocurrencies. Threshold signature schemes mitigate this problem by distributing shares of the secret key on several servers and requiring that enough of them interact to be able to compute a signature. In this paper, we provide a novel threshold protocol for ECDSA, arguably the most relevant signature scheme in practice. Our protocol is the first one where the communication complexity of the preprocessing phase is only logarithmic in the number of ECDSA signatures to be produced later, and it achieves therefore a so-called silent preprocessing. Our protocol achieves active security against any number of arbitrarily corrupted parties.
A Blockchain is a promising infrastructure but it has serious scalability problems, i.e., long block synchronization time and high storage cost. Conventional coarse-grained data deduplication schemes (block or file level) are proved to be ineffective on this problem. Based on comprehensive analysis on typical blockchain workloads, we are the first to propose two new locality concepts: economic and argument locality. To further explore these new localities, we propose a novel fine-grained data deduplication scheme (transaction level) named Alias-Chain to improve the scalability of blockchains. Specifically, Alias-Chain replaces frequently used data, e.g., smart contract arguments, with much shorter aliases to reduce the block size. During prop-agation and preservation of blocks, smaller blocks result in both shorter synchronization time and lower storage cost. Simulation results show the average transfer and SC-call transaction sizes can be reduced by up to 11.23% and 43.23% in native Ethereum, and up to 61.95 % and 77.54 % in Ethereum optimized by state-of-the-art techniques, respectively. Prototyping-based experiments are further conducted on a testbed consisting of up to 3200 miners. The results demonstrate the effectiveness and efficiency of Alias-Chain on reducing block synchronization time and storage cost under typical real-world workloads.
Cameron Hickert, Ali Tekeoglu, Ryan Watson, Joseph Maurio · 8 authors
Incorporating smart technology into critical infrastructure (CI) promises substantial efficiency improvements as networks of machines communicate and make rapid decisions autonomously. Yet the promise of greater efficiency that such cyber-physical systems (CPS) bring is tempered by increased fragility unless machine-to-machine (M2M) trust is enhanced, particularly in Internet-of-Things (IoT) networks. This work makes two contributions toward improving M2M trust. First, it proposes a multifaceted trust framework comprised of identity verification, experience, context, and recommendation scores to enable high-integrity M2M interactions. Second, this trust framework is implemented via an IoT-friendly distributed ledger on a physical testbed, where it is shown to identify and mitigate errors due to a compromised system component. This implementation mirrors real-world IoT systems in which resource- constrained endpoint devices pose trust score computation chal-lenges and the number of devices raises scalability obstacles for information sharing among nodes.
Sri Aravinda Krishnan Thyagarajan, Giulio Malavolta, Pedro Moreno-Sánchez
Trading goods lies at the backbone of the modern economy and the recent advent of cryptocurrencies has opened the door for trading decentralized (digital) assets: A large fraction of the value of cryptocurrencies comes from the inter-currency exchange and trading, which has been arguably the most successful application of decentralized money. The security issues observed with centralized, custodial cryptocurrency exchanges have motivated the design of atomic swaps, a protocol for coin exchanges between any two users. Yet, somewhat surprisingly, no atomic swap protocol exists that simultaneously satisfies the following simple but desired properties: (i) non-custodial, departing from a third party trusted holding the coins from users during the exchange; (ii) universal that is, compatible with all (current and future) cryptocurrencies; (iii) multi-asset, supporting the exchange of multiple coins in a single atomic swap.From a theoretical standpoint, in this work we show a generic protocol to securely swap n coins from any (possible multiple) currencies for $\tilde{n}$ coins of any other currencies, for any n and $\tilde{n}$. We do not require any custom scripting language supported by the corresponding blockchains, besides the bare minimum ability to verify signatures on transactions. For the special case when the blockchains use ECDSA or Schnorr signatures, we design a practically efficient protocol based on adaptor signatures and time-lock puzzles. As a byproduct of our approach, atomic swaps transactions no longer include custom scripts and are identical to standard one-to-one transactions. We also show that our protocol naturally generalizes to any cycle of users, i.e., atomic swaps with more than two participants. To demonstrate the practicality of our approach, we have evaluated a prototypical implementation of our protocol for Schnorr/ECDSA signatures and observed that an atomic swap requires below one second on commodity machines. Even on blockchains with expressive smart contract support (e.g., Ethereum), our approach reduces the on-chain cost both in terms of transaction size and gas cost.
This document provides a clear description of the COLLABS level-2 security components. In particular, it describes fine-grained authorization for constrained environments, relying on distributed ledger technologies for exchanges between different involved mechanisms. We show how COLLABS ledger-based security modules can secure inter-device communications and enhance the trust level in inter-<br> The project COLLABS has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 871518.<br> device collaboration, on several aspects of the Smart Factory lifecycle. We describe how COLLABS ensures that all the data collected from connected objects, and all the actions are authorized following an effective security policy. This document also illustrates the main data flows with sequence diagrams, describing and visualizing processes involving each component, as well as mapping of COLLABS level-2 security components to the use case scenarios.
K. Vijayalakshmi, S. Nikkath Bushra, Nalini Subramanian, Veeralakshmi Ponnuramu
In order to overcome all the flaws and limitations related to the existing system in the medical field regarding the storing, sharing and accessing the medical data or records of the users, this research study come up with a solution to solve this issue by creating a user friendly mobile application to store all the medical information of the users in a single platform, which enables easy sharing, storing and accessing of medical records of the users. This system brings up an easy way to store the medical records of the users in a mobile application using blockchain technology. Since blockchain technology is being used in the system, it enables quite a good amount of security and enables the safety of the data being stored in the application. Once the account is created for a particular patient and all the data is entered by the hospital admins, the user can then have an account for themselves and can also track their medical information in the app as to who are the ones viewing their data. The hospital can feed all kinds of patient information in the application and can save and store them. The data in the application is stored safely and securely ensuring high levels of security and thus keeping the data safe without getting lost and enabling a trustworthy interface to store people's health-related data. Medical data such as scans, x-rays, test reports, prescriptions etc., can be stored in the application in different formats such as images, pdf etc.
Yeonouk Chu, Jae‐Ho Lee, Sung-Joong Kim, Hyun-Joong Kim · 6 authors
Due to the growth of the internet and communication technologies, electronic financial systems are becoming popular. Physical cash is losing its preeminence, and digital numbers on computers represent money. However, electronic financial systems, mostly operated by private entities, have defects to be compensated for, such as high charges for using the system, security issues, and the problem of exclusion. As a solution, many countries around the world are considering central bank digital currency. For central bank digital currency to be utilized as a national legal tender, it must be universal and accessible regardless of time and place, similar to physical cash. Therefore, offline payment functions that extend the accessibility of central bank digital currency are becoming attractive. However, due to the characteristics of the electronic financial system, central bank digital currency is vulnerable to possible malicious behaviors in offline situations, such as blackouts and system shutdowns. This paper reviews research studies that deal with security matters related to the offline payment function of central bank digital currency. Offline payment solutions, including central bank digital currency and other electronic financial systems, such as electronic cash and cryptocurrency, are reviewed, and supplemental methods to improve the offline payment solutions of central bank digital currency based on trusted execution environment devices are suggested.
Blockchain has received great attention in academia and industry due to its decentralization and immutability. From the perspective of transaction processing, blockchain is a distributed shared ledger and database with the characteristics of decentralization, traceability, and transparency. These features ensure the security of blockchain’s reliability. However, because a blockchain network requires complex consensus verification between users, it causes problems such as a high cost of data exchange and a low system throughput. Such problems are aggravated when executing a cross-chain transaction, as it is particularly important to ensure the atomicity and isolation of transactions across the blockchain. Considering this, in this paper, we propose the cross-chain transaction processing flow of EOVPC and efficient transaction processing based on version control. Different from the existing cross-chain transaction approaches based on locking, we propose optimistic approaches in which the updated data can be used immediately, with a rolling back procedure that guarantees atomicity. We conducted extensive experiments, which show that our approaches can improve the throughput and success rate significantly.
The cloud computing technology has emerged, developed, and matured in recent years, consequently commercializing remote outsourcing storage services. An increasing number of companies and individuals have chosen the cloud to store their data. However, accidents, such as cloud server downtime, cloud data loss, and accidental deletion, are serious issues for some applications that need to run around the clock. For some mission and business-critical applications, the continuous availability of outsourcing storage services is also necessary to protect users' outsourced data during downtime. Nevertheless, ensuring the continuous availability of data in public cloud data integrity auditing protocols leads to data privacy issues because auditors can obtain the data content of users by a sufficient number of storage proofs. Therefore, protecting data privacy is a burning issue. In addition, existing data integrity auditing schemes that rely on semi-trusted third-party auditors have several security problems, including single points of failure and performance bottlenecks. To deal with these issues, we propose herein a blockchain-based continuous data integrity checking protocol with zero-knowledge privacy protection. We realize a concrete construction by using a verifiable delay function with high efficiency and proof of retrievability, and prove the security of the proposal in a random oracle model. The proposed construction supports dynamic updates for the outsourced data. We also design smart contracts to ensure fairness among the parties involved. Finally, we implement the protocols, and the experimental results demonstrate the efficiency of the proposed protocol.
Tanusree Sharma, Zhixuan Zhou, Andrew Miller, Yan Wang
Smart contracts are self-executing programs that run on blockchains (e.g., Ethereum). 680 million US dollars worth of digital assets controlled by smart contracts have been hacked or stolen due to various security vulnerabilities in 2021. Although security is a fundamental concern for smart contracts, it is unclear how smart contract developers approach security. To help fill this research gap, we conducted an exploratory qualitative study consisting of a semi-structured interview and a code review task with 29 smart contract developers with diverse backgrounds, including 10 early stage (less than one year of experience) and 19 experienced (2-5 years of experience) smart contract developers. Our findings show a wide range of smart contract security perceptions and practices including various tools and resources they used. Our early-stage developer participants had a much lower success rate (15%) of identifying security vulnerabilities in the code review task than their experienced counterparts (55%). Our hierarchical task analysis of their code reviews implies that just by accessing standard documentation, reference implementations and security tools is not sufficient. Many developers checked those materials or used a security tool but still failed to identify the security issues. In addition, several participants pointed out shortcomings of current smart contract security tooling such as its usability. We discuss how future education and tools could better support developers in ensuring smart contract security.
The publicly accessible feature of edge servers leads to the threat of malicious access to the data stored on the server and a series of security problems such as the leakage of user data privacy and the destruction of integrity. Data custody causes the separation of user ownership and management rights and brings potential security risks of data theft and destruction. Among them, for the integrity of the data uploaded by the terminal, the current protection mechanism mostly verifies the identity of the visitor or encrypts the data, but the role of verification is mostly assumed by the server, and it is impossible to avoid the collusion of edge servers with malicious intruders. In this paper, a distributed virtual machine agent (VMA) is designed and implemented, an edge cloud data integrity monitoring framework is built, and the verification protocol based on blockchain is proposed, which achieves trusted verification without relying on a trusted third party. Also, a prototype system of edge cloud data integrity protection based on blockchain is constructed to prevent data corruption. The results of security proof and experimental verification show that the mechanism based on blockchain technology can defend against three attacks of cloud service providers, has superior computation, and reduces the storage costs to protect the integrity of user data.
Pengfei Wang, Pan Bo, Tao Qian, Yang Changqing · 5 authors
Aiming at the safety and efficiency problems in the whole life cycle management of aviation equipment, propose an efficient solution based on federated blockchain. Firstly, the data collected by the terminal sensing device is hash transformed through the blockchain system, and the initial data security is achieved by using the irreversibility principle of the hash algorithm while reducing the data volume of a single transaction in the block; secondly, the block is generated by the representative nodes elected through the Delegated-Proof of Stake (DPoS), and the consensus algorithm of the blockchain data verification adopts the delegated Byzantine Fault-Tolerance (DBFT) consensus algorithm to improve the consensus efficiency; finally, the transaction time curves are fitted and plotted according to the number of participating nodes, block size and network bandwidth in the simulation experiments to calculate the transaction efficiency under different situations. The experimental results show that the federated chain system is proved to achieve secure and efficient aviation equipment history storage and traceability.
Storage is a promising application for permission-less blockchains. Before blockchain, cloud storage was hosted by a trusted service provider. The centralized system controls the permission of the data access. In web3, users own their data. Data must be encrypted in a permission-less decentralized storage network, and the permission control should be pure cryptographic. Proxy re-encryption (PRE) is ideal for cryptographic access control, which allows a proxy to transfer Alice’s ciphertext to Bob with Alice’s authorization. The encrypted data are stored in several copies for redundancy in a permission-less decentralized storage network. The redundancy suffers from the outsourcing attack. The malicious resource provider may fetch the content from others and respond to the verifiers. This harms data integrity security. Thus, proof-of-replication (PoRep) must be applied to convince the user that the storage provider is using dedicated storage. PoRep is an expensive operation that encodes the original content into a replication. Existing PRE schemes cannot satisfy PoRep, as the cryptographic permission granting generates an extra ciphertext. A new ciphertext would result in several expensive replication operations. We searched most of the PRE schemes for the combination of the cryptographic methods to avoid transforming the ciphertext. Therefore, we propose a new PRE scheme. The proposed scheme does not require the proxy to transfer the ciphertext into a new one. It reduces the computation and operation time when allowing a new user to access a file. Furthermore, the PRE scheme is CCA (chosen-ciphertext attack) security and only needs one key pair.