Blockchain technology has evolved from being an immutable ledger of\ntransactions for cryptocurrencies to a programmable interactive the environment\nfor building distributed reliable applications. Although, blockchain technology\nhas been used to address various challenges, to our knowledge none of the\nprevious work focused on using blockchain to develop a secure and immutable\nscientific data provenance management framework that automatically verifies the\nprovenance records. In this work, we leverage blockchain as a platform to\nfacilitate trustworthy data provenance collection, verification, and\nmanagement. The developed system utilizes smart contracts and open provenance\nmodel (OPM) to record immutable data trails. We show that our proposed\nframework can efficiently and securely capture and validate provenance data,\nand prevent any malicious modification to the captured data as long as the\nmajority of the participants are honest.\n
Transactive microgrids are emerging as a transformative solution for the\nproblems faced by distribution system operators due to an increase in the use\nof distributed energy resources and a rapid acceleration in renewable energy\ngeneration, such as wind and solar power. Distributed ledgers have recently\nfound widespread interest in this domain due to their ability to provide\ntransactional integrity across decentralized computing nodes. However, the\nexisting state of the art has not focused on the privacy preservation\nrequirement of these energy systems -- the transaction level data can provide\nmuch greater insights into a prosumer's behavior compared to smart meter data.\nThere are specific safety requirements in transactive microgrids to ensure the\nstability of the grid and to control the load. To fulfil these requirements,\nthe distribution system operator needs transaction information from the grid,\nwhich poses a further challenge to the privacy-goals. This problem is made\nworse by requirement for off-blockchain communication in these networks. In\nthis paper, we extend a recently developed trading workflow called PETra and\ndescribe our solution for communication and transactional anonymity.\n
Transactive microgrids are emerging as a transformative solution for the problems faced by distribution system operators due to an increase in the use of distributed energy resources and a rapid acceleration in renewable energy generation, such as wind and solar power. Distributed ledgers have recently found widespread interest in this domain due to their ability to provide transactional integrity across decentralized computing nodes. However, the existing state of the art has not focused on the privacy preservation requirement of these energy systems -- the transaction level data can provide much greater insights into a prosumer's behavior compared to smart meter data. There are specific safety requirements in transactive microgrids to ensure the stability of the grid and to control the load. To fulfil these requirements, the distribution system operator needs transaction information from the grid, which poses a further challenge to the privacy-goals. This problem is made worse by requirement for off-blockchain communication in these networks. In this paper, we extend a recently developed trading workflow called PETra and describe our solution for communication and transactional anonymity.
Henrique Rocha, Sté́phane Ducasse, Marcus Denker, Jason Lecerf
Solidity is a language used to implement smart contracts on a blockchain platform. Since its initial conception in 2014, Solidity has evolved into one of the major languages for the Ethereum platform as well as other blockchain technologies. Due to its popularity, there are many tools specifically designed to handle smart contracts written in Solidity. However, there is a lack of tools for Pharo to handle Solidity contracts. Therefore, we implemented a parser using SmaCC to serve as a base for further developing Solidity support in Pharo. In this paper, we describe the parser creation, the irregularities we found in the Solidity grammar specification, and common practices on how to adapt the grammar to an LR type parser. Our experiences with parsing the Solidity language using SmaCC may help other developers trying to convert similar grammars.
Nabil Rifi, Elie Rachkidi, Nazim Agoulmine, Nada Chendeb Taher
In the past few years, the number of wireless devices connected to the Internet has increased to a number that could reach billions in the next few years. While cloud computing is being seen as the solution to process this data, security challenges could not be addressed solely with this technology. Security problems will continue to increase with such a model, especially for private and sensitive data such as data personal and medical data collected with more and more sophisticated connected devices (forming the IoT). Thus the need for a fully decentralized peer to peer and secure technology to overcome these problems. The blockchain Technology is a promising approach giving the properties it brings to the field. This paper illustrates an architecture based on blockchain technology, and a protocol for data access, using smart contracts and a publisher-subscriber mechanism.
An appealing feature of blockchain technology is smart contracts. A smart contract is executable code that runs on top of the blockchain to facilitate, execute and enforce an agreement between untrusted parties without the involvement of a trusted third party. In this paper, we conduct a systematic mapping study to collect all research that is relevant to smart contracts from a technical perspective. The aim of doing so is to identify current research topics and open challenges for future studies in smart contract research. We extract 24 papers from different scientific databases. The results show that about two thirds of the papers focus on identifying and tackling smart contract issues. Four key issues are identified, namely, codifying, security, privacy and performance issues. The rest of the papers focuses on smart contract applications or other smart contract related topics. Research gaps that need to be addressed in future studies are provided.
Abstract The smart partnership framework introduced in this article is derived from extensive, on-site interviews with nonprofit and public contract managers conducted in several grounded research projects between 2011 and 2015 and from the research literature on contracting. The framework demonstrates the continuing explanatory power of resource dependence theory that disentangles the formidable influence of the public policy environment on organizational action. It is intended to provide a coherent guide for practice by enabling nonprofit managers in the social services field to navigate the current intense environmental uncertainty in which cross-sector contracting relationships between government agencies and nonprofit organizations are embedded. By providing an accessible way to understand an extraordinarily complex set of inter-organizational dynamics, the model offers a research-based definition and clear visualization of what it means to be a smart partner. It highlights the necessity of understanding the norms, expectations, structures, processes, and culture within which sector counterpart contract managers operate. Fundamental to the range of managerial strategies that the framework calls for is the need explicitly to attend to relationship building, to patterns of variation in relationships over time, and to their probable consequences. The integrative model consists of three inter-related organizational competencies and a number of secondary competencies. Competency 1: understand the dynamic nature of contracting relationships; secondary competencies: recognize predictable variations in relationships; comprehend the importance of multiple institutional logics. Competency 2: develop and sustain capacity for strategic adaptation; secondary competencies: build external and internal learning capacity; discern power shifts in inter-organizational relationships; maintain capability for strategic repositioning. Competency 3: participate proactively in shaping policy change; secondary competencies: attend to relationship development and nurturance; build trust and credibility.
Since its inception, the blockchain technology has shown promising application prospects. From the initial cryptocurrency to the current smart contract, blockchain has been applied to many fields. Although there are some studies on the security and privacy issues of blockchain, there lacks a systematic examination on the security of blockchain systems. In this paper, we conduct a systematic study on the security threats to blockchain and survey the corresponding real attacks by examining popular blockchain systems. We also review the security enhancement solutions for blockchain, which could be used in the development of various blockchain systems, and suggest some future directions to stir research efforts into this area.
Open access
3 source records
Blockchain Technology Applications and Security
Advanced Steganography and Watermarking Techniques
Tien Tuan Anh Dinh, Rui Liu, Meihui Zhang, Gang Chen · 6 authors
Blockchain technologies are gaining massive momentum in the last few years. Blockchains are distributed ledgers that enable parties who do not fully trust each other to maintain a set of global states. The parties agree on the existence, values, and histories of the states. As the technology landscape is expanding rapidly, it is both important and challenging to have a firm grasp of what the core technologies have to offer, especially with respect to their data processing capabilities. In this paper, we first survey the state of the art, focusing on private blockchains (in which parties are authenticated). We analyze both in-production and research systems in four dimensions: distributed ledger, cryptography, consensus protocol, and smart contract. We then present BLOCKBENCH, a benchmarking framework for understanding performance of private blockchains against data processing workloads. We conduct a comprehensive evaluation of three major blockchain systems based on BLOCKBENCH, namely Ethereum, Parity, and Hyperledger Fabric. The results demonstrate several trade-offs in the design space, as well as big performance gaps between blockchain and database systems. Drawing from design principles of database systems, we discuss several research directions for bringing blockchain performance closer to the realm of databases.
Mustafa Al-Bassam, Alberto Sonnino, Shehar Bano, Dave Hrycyszyn · 5 authors
Chainspace is a decentralized infrastructure, known as a distributed ledger, that supports user defined smart contracts and executes user-supplied transactions on their objects. The correct execution of smart contract transactions is verifiable by all. The system is scalable, by sharding state and the execution of transactions, and using S-BAC, a distributed commit protocol, to guarantee consistency. Chainspace is secure against subsets of nodes trying to compromise its integrity or availability properties through Byzantine Fault Tolerance (BFT), and extremely high-auditability, non-repudiation and `blockchain' techniques. Even when BFT fails, auditing mechanisms are in place to trace malicious participants. We present the design, rationale, and details of Chainspace; we argue through evaluating an implementation of the system about its scaling and other features; we illustrate a number of privacy-friendly smart contracts for smart metering, polling and banking and measure their performance.
Cüneyt Gürcan Akçora, Yulia R. Gel, Murat Kantarcıoğlu
Bitcoin and its underlying technology, blockchain, have gained significant popularity in recent years. Satoshi Nakamoto designed Bitcoin to enable a secure, distributed platform without the need for central authorities, and blockchain has been hailed as a paradigm that will be as impactful as Big Data, Cloud Computing, and Machine Learning. Blockchain incorporates innovative ideas from various fields, such as public-key encryption and distributed systems. As a result, readers often encounter resources that explain Blockchain technology from a single perspective, leaving them with more questions than answers. In this primer, we aim to provide a comprehensive view of blockchain. We will begin with a brief history and introduce the building blocks of the blockchain. As graph mining is a major area of blockchain analysis, we will delve into the graph-theoretical aspects of Blockchain technology. We will also discuss the future of blockchain and explain how extensions such as smart contracts and decentralized autonomous organizations will function. Our goal is to provide a concise but complete description of blockchain technology that is accessible to readers with no prior expertise in the field.
Cloud computing has become an irreversible trend. Together comes the pressing need for verifiability, to assure the client the correctness of computation outsourced to the cloud. Existing verifiable computation techniques all have a high overhead, thus if being deployed in the clouds, would render cloud computing more expensive than the on-premises counterpart. To achieve verifiability at a reasonable cost, we leverage game theory and propose a smart contract based solution. In a nutshell, a client lets two clouds compute the same task, and uses smart contracts to stimulate tension, betrayal and distrust between the clouds, so that rational clouds will not collude and cheat. In the absence of collusion, verification of correctness can be done easily by crosschecking the results from the two clouds. We provide a formal analysis of the games induced by the contracts, and prove that the contracts will be effective under certain reasonable assumptions. By resorting to game theory and smart contracts, we are able to avoid heavy cryptographic protocols. The client only needs to pay two clouds to compute in the clear, and a small transaction fee to use the smart contracts. We also conducted a feasibility study that involves implementing the contracts in Solidity and running them on the official Ethereum network.
An existing pseudo-commodity and a smart contracts framework allow the creation of a purely automatic and self-sufficient price-stable cryptocurrency, without human intervention. This new currency, we denominated Toroid or TRD, can be used more extensively for commerce than pseudo commodity cryptocurrencies due to its lower volatility. Also, is suitable for investment, as the tokens in each account multiply, return interest, when the market grows. Like the controlled fiat money of a central bank plus the benefits of an inflation-adjusted perpetuity bond. Collateral in base coin, for example BTC or ETH, can be added to bootstrap your own Toroid investment or withdrawed after a very small investment period. So, the Toroids are not created from nothing nor have a limited monetary base. The minimum investment period can be very small, for example one day, and you keep the interest but you can return the Toroids and refund your collateral. That is a one-side only peg to a deflationary crypto-commodity. The stability is guaranteed by endogenous measurements of number of transactions and wallet pro-rated rebasement of balance to reduce volatility of price. Each account has its own rebasement due to the account creation timestamp. Rebasement control mechanism is progressive during initial bootstrap period because price manipulation protection is more severe when the capital involved is smaller. Rebasement has a quick positive start to incentivize early adopters that see only big growth in their TRD account during bootstrap period. Finally, the new rebasement control makes it economically infeasible for an attacker targeting the coin with manipulated transaction volume if we set the minimum rebasement greater than profits from massive currency manipulation.
A developing field of interest for the distributed systems and applied cryptography community is that of smart contracts: self-executing financial instruments that synchronize their state, often through a blockchain. One such smart contract system that has seen widespread practical adoption is Ethereum, which has grown to secure approximately 30 billion USD of currency value and in excess of 300,000 daily transactions. \n \nUnfortunately, the rise of these technologies has been marred by a repeated series of security vulnerabilities and high pro file contract failures. To address these failures, the Ethereum community has turned to formal verification and program analysis which show great promise due to the computational simplicity and bounded-time execution inherent to smart contracts. Despite this, no fully formal, rigorous, comprehensive, and executable semantics of the EVM (Ethereum Virtual Machine) currently exists, leaving a lack of rigor on which to base such tools. \n \nIn this work, we present KEVM, the first fully executable formal semantics of the EVM, the bytecode language in which smart contracts are executed. We create this semantics in a framework for executable \nsemantics, the K framework. We show that our semantics not only passes the official 40,683-test stress test suite for EVM implementations, but also reveals ambiguities and potential sources of error in the existing \non-paper formalization of EVM semantics on which our work is based. \n These properties make KEVM an ideal formal reference implementation against which other implementations can be evaluated. \n \nWe proceed to argue for a semantics-first formal verification approach for EVM contracts, and demonstrate its practicality by using KEVM to verify practically important properties over the arithmetic operation of an \nexample smart contract and the correct operation of a token transfer function in a second contract. We show that our approach is feasible and not computationally restrictive. We hope that our work serves as the base for the development of a wide range of useful formally derived tools for Ethereum, including model checkers, certified compilers, and program equivalence checkers.
We present an architecture for peer-to-peer energy markets which can guarantee that operational constraints are respected and payments are fairly rendered, without relying on a centralized utility or microgrid aggregator. We demonstrate how to address trust, security, and transparency issues by using blockchains and smart contracts, two emerging technologies which can facilitate decentralized coordination between non-trusting agents. While blockchains are receiving considerable interest as a platform for distributed computation and data management, this is the first work to examine their use to facilitate distributed optimization and control. Using the Alternating Direction Method of Multipliers (ADMM), we pose a decentralized optimal power flow (OPF) model for scheduling a mix of batteries, shapable loads, and deferrable loads on an electricity distribution network. The DERs perform local optimization steps, and a smart contract on the blockchain serves as the ADMM coordinator, allowing the validity and optimality of the solution to be verified. The optimal schedule is securely stored on the blockchain, and payments can be automatically, securely, and trustlessly rendered without requiring a microgrid operator.
Smart contracts are contracts essentially in form of Computer Codes, where the terms of the contract are enforced by the logic of the program’s execution. They do not require judgement or skill of any specialist. This allows us to form a vastly strong system of checks-and-balances, in a trust-less and decentralised manner. Smart contracts also gain the benefit of global transferability, without sacrificing any local knowledge. It’s both cost and time effective. Smart Contracts would dramatically reduce the costs of developing, maintain and securing our relationships. It’s very similar to an online Chessboard game, where the players would design the rules of the game before they are willing to play. And once the rules are agreed on, the Contract would act as a board manager, this allows the parties to move freely but within the rules of the game. Although, enforceability is a challenge to proper working of Smart Contracts, many international conventions can be used to govern the working of such contracts. There exists a clear lack of theoretical framework in this respect. This paper tries to draw out such a theoretical framework by identifying the different modes for regulating and enforcing smart contracts in multiple jurisdictions. Establishment of a legal framework regulating Smart Contracts would be a giant leap in the field of Contractual Laws.
Reproducibility, data sharing, personal data privacy concerns and patient enrolment in clinical trials are huge medical challenges for contemporary clinical research. A new technology, Blockchain, may be a key to addressing these challenges and should draw the attention of the whole clinical research community.Blockchain brings the Internet to its definitive decentralisation goal. The core principle of Blockchain is that any service relying on trusted third parties can be built in a transparent, decentralised, secure "trustless" manner at the top of the Blockchain (in fact, there is trust, but it is hardcoded in the Blockchain protocol via a complex cryptographic algorithm). Therefore, users have a high degree of control over and autonomy and trust of the data and its integrity. Blockchain allows for reaching a substantial level of historicity and inviolability of data for the whole document flow in a clinical trial. Hence, it ensures traceability, prevents a posteriori reconstruction and allows for securely automating the clinical trial through what are called Smart Contracts. At the same time, the technology ensures fine-grained control of the data, its security and its shareable parameters, for a single patient or group of patients or clinical trial stakeholders.In this commentary article, we explore the core functionalities of Blockchain applied to clinical trials and we illustrate concretely its general principle in the context of consent to a trial protocol. Trying to figure out the potential impact of Blockchain implementations in the setting of clinical trials will shed new light on how modern clinical trial methods could evolve and benefit from Blockchain technologies in order to tackle the aforementioned challenges.
Open access
Ethics in Clinical Research
Artificial Intelligence in Healthcare and Education
Blockchains such as Bitcoin and Ethereum execute payment transactions securely, but their performance is limited by the need for global consensus. Payment networks overcome this limitation through off-chain transactions. Instead of writing to the blockchain for each transaction, they only settle the final payment balances with the underlying blockchain. When executing off-chain transactions in current payment networks, parties must access the blockchain within bounded time to detect misbehaving parties that deviate from the protocol. This opens a window for attacks in which a malicious party can steal funds by deliberately delaying other parties' blockchain access and prevents parties from using payment networks when disconnected from the blockchain. We present Teechain, the first layer-two payment network that executes off-chain transactions asynchronously with respect to the underlying blockchain. To prevent parties from misbehaving, Teechain uses treasuries, protected by hardware trusted execution environments (TEEs), to establish off-chain payment channels between parties. Treasuries maintain collateral funds and can exchange transactions efficiently and securely, without interacting with the underlying blockchain. To mitigate against treasury failures and to avoid having to trust all TEEs, Teechain replicates the state of treasuries using committee chains, a new variant of chain replication with threshold secret sharing. Teechain achieves at least a 33x higher transaction throughput than the state-of-the-art Lightning payment network. A 30-machine Teechain deployment can handle over 1 million Bitcoin transactions per second.
Blockchains such as Bitcoin and Ethereum execute payment transactions securely, but their performance is limited by the need for global consensus. Payment networks overcome this limitation through off-chain transactions. Instead of writing to the blockchain for each transaction, they only settle the final payment balances with the underlying blockchain. When executing off-chain transactions in current payment networks, parties must access the blockchain within bounded time to detect misbehaving parties that deviate from the protocol. This opens a window for attacks in which a malicious party can steal funds by deliberately delaying other parties' blockchain access and prevents parties from using payment networks when disconnected from the blockchain. We present Teechain, the first layer-two payment network that executes off-chain transactions asynchronously with respect to the underlying blockchain. To prevent parties from misbehaving, Teechain uses treasuries, protected by hardware trusted execution environments (TEEs), to establish off-chain payment channels between parties. Treasuries maintain collateral funds and can exchange transactions efficiently and securely, without interacting with the underlying blockchain. To mitigate against treasury failures and to avoid having to trust all TEEs, Teechain replicates the state of treasuries using committee chains, a new variant of chain replication with threshold secret sharing. Teechain achieves at least a 33x higher transaction throughput than the state-of-the-art Lightning payment network. A 30-machine Teechain deployment can handle over 1 million Bitcoin transactions per second.
Blockchains such as Bitcoin and Ethereum execute payment transactions securely, but their performance is limited by the need for global consensus. Payment networks overcome this limitation through off-chain transactions. Instead of writing to the blockchain for each transaction, they only settle the final payment balances with the underlying blockchain. When executing off-chain transactions in current payment networks, parties must access the blockchain within bounded time to detect misbehaving parties that deviate from the protocol. This opens a window for attacks in which a malicious party can steal funds by deliberately delaying other parties' blockchain access and prevents parties from using payment networks when disconnected from the blockchain. We present Teechain, the first layer-two payment network that executes off-chain transactions asynchronously with respect to the underlying blockchain. To prevent parties from misbehaving, Teechain uses treasuries, protected by hardware trusted execution environments (TEEs), to establish off-chain payment channels between parties. Treasuries maintain collateral funds and can exchange transactions efficiently and securely, without interacting with the underlying blockchain. To mitigate against treasury failures and to avoid having to trust all TEEs, Teechain replicates the state of treasuries using committee chains, a new variant of chain replication with threshold secret sharing. Teechain achieves at least a 33x higher transaction throughput than the state-of-the-art Lightning payment network. A 30-machine Teechain deployment can handle over 1 million Bitcoin transactions per second.
General Insurance occupies a strong position in today's market. It has a centralized way of operation, which makes it inefficient, less transparent, with trust problems and creates conflicts of interest between insurance companies and policyholders. Furthermore, it's an industry with relative difficulty in innovation, which contrasts with today's services powered by new technologies. New disruptive technologies have the capacity to compromise the value chain of traditional insurance, creating a big problem in its stability and future. Associated to this new kind of technologies, comes a new way of thinking perpetuated by the new generations based on the new trend of sharing economy. They give priority to new technology based services, which are decentralized, more convenient, more price competitive, transparent, and efficient and they prefer services which put the user more in control instead of the current less personalized options. New business models such as Social Insurance, are being developed and powered by new technologies and this new way of thinking. Social Insurance enables people in need of insurance to connect and pool their money and risks. It offers coverage that is cheaper, more transparent, and more relevant to the customer. Members of this type of insurance are both policyholders and underwriters. All these factors compromise the future of traditional insurance companies and their business model. The main goal is to create a new business model in order to adapt insurance companies to the new trend of shared economy. This new business model is going to be focused on health insurance, based in peer to peer communication and is going to be backed up by a business case and a prototype powered by a blockchain database. Blockchain is a decentralized transaction ledger shared amongst all nodes participating in the system. Every node has an updated copy of the database and cannot update it without the consensus of the network, removing the need for having a central authority or trusted third party to monitor the system. Each Blockchain implementation may have its own consensus mechanism (e.g. Proof-of-Work and Proof-of-Stake) to ensure that one node on its own cannot change the database without being validated by the network. Bitcoin is the world's most well-known Blockchain implementation, a public ledger for all transactions made in with a digital currency. However, Blockchain technology can be applied to multiple use cases and industries using Smart Contracts (a collection of code that runs on the network) to define the rules of the business. It fits the purpose for this business model, because it has peer to peer communication by default and has no central authority, making the service more efficient and transparent.