Given the ongoing transition towards a more decentralised and adaptive energy system, the potential of blockchain-enabled smart contracts for the energy sector is being increasingly recognised. Due to their self-executing, customisable and tamper-proof nature, they are seen as a key technology for enabling the transition to a more efficient, transparent and transactive energy market. The applications of smart contracts include coordination of smart electric vehicle charging, automated demand-side response, peer-to-peer energy trading and allocation of the control duties amongst the network operators. Nevertheless, their use in the energy sector is still in its early stages as there are many open challenges related to security, privacy, scalability and billing. In this paper, we systematically review 178 peer-reviewed publications and 13 innovation projects, providing a thorough analysis of the strengths and weaknesses of smart contracts used in the energy sector. This work offers a broad perspective on the opportunities and challenges that stakeholders using this technology face, in both current and emergent markets, such as peer-to-peer energy trading platforms. To provide a roadmap for researchers and practitioners interested in the technology, we propose a systematic model of the smart contracting process, by developing a novel 6-layer architecture, as well as presenting a sample energy contract in pseudocode form and as open-source code. Our analysis focuses on the two mainstream application areas we identify for smart contract use in this area: energy and flexibility trading, and distributed control. The paper concludes with a comprehensive, critical discussion of the advantages and challenges that must be addressed in the area of smart contracts and blockchains in energy, and a set of recommendations that researchers and developers should consider when applying smart contracts to energy system settings. 

https://doi.org/10.1016/j.rser.2021.112013

Smart contracts in energy systems: A systematic review of fundamental approaches and implementations

Blockchain technology started as the backbone for cryptocurriencies and it has emerged as one of the most interesting technologies of the last decade. It is a new paradigm able to modify the way how industries transact. Today, the industries’ concern is about their ability to handle a high volume of data transactions per second while preserving both decentralization and security. Both decentralization and security are guaranteed by the mathematical strength of cryptographic primitives. There are two main approaches to achieve consensus: the Proof-of-Work based blockchains—PoW—and the Proof-of-Stake—PoS. Both of them come with some pros and drawbacks, but both rely on cryptography. In this survey, we present a review of the main consensus procedures, including the new consensus proposed by Algorand: Pure Proof-of-Stake—Pure PoS. In this article, we provide a framework to compare the performances of PoW, PoS and the Pure PoS, based on throughput and scalability.

A Survey on Blockchain Consensus with a Performance Comparison of PoW, PoS and Pure PoS

Currently, an increasing number of third-party applications exploit the Bitcoin blockchain to store tamper-proof records of their executions, immutably. For this purpose, they leverage the few extra bytes available for encoding custom metadata in Bitcoin transactions. A sequence of records of the same application can thus be abstracted as a stand-alone subchain inside the Bitcoin blockchain. However, several existing approaches do not make any assumptions about the consistency of their subchains, either (i) neglecting the possibility that this sequence of messages can be altered, mainly due to unhandled concurrency, network malfunctions, application bugs, or malicious users, or (ii) giving weak guarantees about their security. To tackle this issue, in this paper, we propose an improved version of a consensus protocol formalized in our previous work, built on top of the Bitcoin protocol, to incentivize third-party nodes to consistently extend their subchains. Besides, we perform an extensive analysis of this protocol, both defining its properties and presenting some real-world attack scenarios, to show how its specific design choices and parameter configurations can be crucial to prevent malicious practices.

https://www.mdpi.com/2079-3197/8/3/67/pdf

Analysis of a Consensus Protocol for Extending Consistent Subchains on the Bitcoin Blockchain

General Concept of Real Estate Tokenization on Blockchain: The Right to Choose

This paper presents a concept of real estate tokenization, which includes legal, technological, and organizational aspects. The research introduces a theory of a Title Token - a digital record of ownership on the blockchain. It is discussed the principle of technological neutrality, where the traditional land registry is not necessarily abandoned in favor of blockchains, but instead, people gain the right to choose. Nowadays, public administrations use central-server databases, giving no alternatives for citizens. Recognition of the right of citizens to choose which technology to apply for managing their property rights creates a basis for free competition and the development of new technologies for better public services. Decentralized distributed ledgers are the key to decentralization. They enable more secure automation of legal procedures. On the contrary, centralization is a source of many issues in governance: abuse of power, corruption, inefficient governance, and high costs, slowness and complexity of bureaucratic procedures. With automation and reduction of intermediaries, the role of the government does not decrease but significantly changes, i.e. land cadaster bodies should not be monopolistic providers on the market. The paper introduces a theoretical basis for developing a new type of property registries.

https://papers.ssrn.com/sol3/Delivery.cfm/SSRN_ID3632721_code3857402.pdf?abstractid=3569419&mirid=1

General Concept of Real Estate Tokenization on Blockchain

Blockchain based systems become more and more prominent. While starting by developing (crypto)currency payment schemes, a lot of the latest development goes in the direction of executing source code directly in the peer-to-peer network blockchains are usually built on. These so called smart contracts have become popular in order to reduce the amount of necessary middle-mans involved in different processes. Despite the large amount of research already invested in the design of languages which support smart contracts, there are still a lot of problems in the existing approaches, regularly resulting in security flaws. One of these problems is the complexity of the used languages. Therefore, this paper provides an evaluation of currently deployed smart contracts with respect of the requirements of those contracts concerning computability. The finding is that most of the currently deployed smart contracts do not need Turing complete languages, but could also be implemented based on a simpler design of the underlaying language.

Do Smart Contract Languages Need to Be Turing Complete

Programming is not a simple task. Besides, the learning of syntax, the obstacles often seem insurmountable for the beginner. Syntax errors frustrate and distract attention from the actual algorithms and logic that need to be understood. With the help of visual programming, syntax errors can be avoided as much as possible by using predefined graphical boxes, which, due to their shape, can only be connected correctly to form a program. Moreover, Smart Contracts are mainly designed to exclude the need to trust a third party. Here using Visual programming makes perfect sense by making the creation of Smart Contracts much simpler without the help of a developer. Another advantage of Visual Programming Language (VPL) in Smart Contract creation is that the terms and conditions in Contracts can be read and understood from non-developers. In this research we aim to implement a Visual Smart Contract Creator and to conduct an empirical evaluation, which on the one hand, measures the semantic understandability of a visual representation of a Smart Contract created with our tool and compares it to its textual representation in Ride programming language. On the other hand, we evaluate the user acceptance of the tool.

Implementation and Evaluation of a Visual Programming Language in the Context of Blockchain.

Visual programming has become a term that stands for intuitive software development. It dispenses largely with textual notation and instead uses graphical program modules. The use of visual techniques is connected with the hope, among other things, to be able to create and understand programs more easily and better than before, which would open up access to software development for non-programmers. This could lead to a reduction of the enormous application backlog in many places. In this research, we design and build a web-based Visual Query builder tool to query the Waves blockchain database, using a flow-based programming language as well as an empirical evaluation of the tool that, on the one hand, measures the semantic understandability of a visual representation of a query, and compare it to its textual representation in SQL. On the other hand, we evaluate the user acceptance of the tool.

Implementation and Evaluation of a Visual Query Language in the Context of Blockchain

Blockchain comes up to solve centralization problems and to be an alternative solution to traditional finance. This technology seems to be very promising and has proven a big efficiency in ensuring trust among the network. It innovates and proposes new forms of governance and capital allocation, it promises decentralized financial services of credit, exchange, insurance, etc. It is the interweaving of computer programs, called smart contracts in a decentralized network, which replace traditional intermediaries and automate business processes. To make smart contracts in the blockchain context consistent and worthy, they must rely on solid data from the outside world, such as market prices observed on all exchange places for example. Blockchains are autonomous systems that are not natively designed to integrate data from the “outside”, thus, oracles are external systems that solve the problem of feeding an isolated network with data from the outside. On the other hand, these systems are centralized, consequently, they grant a high risk of data corruption and unreliability issues.

Farouk Hdhili

Papers

Do Smart Contract Languages Need to Be Turing Complete

Implementation and Evaluation of a Visual Programming Language in the Context of Blockchain.

Implementation and Evaluation of a Visual Query Language in the Context of Blockchain

A Dag Based Decentralized Oracle Model: Implementation and Evaluation