In the last few years, blockchain (also known as distributed ledger), the underlying technology of the permissionless or public Bitcoin network, has become very popular for use in private or permissioned environments. Computer companies like IBM and Microsoft, and many key players in different vertical industry segments have recognized the utility of blockchains for securely managing assets (physical/digital) other than cryptocurrencies. IBM did some pioneering work by architecting and implementing a private blockchain system, and then open sourcing it. That system, which has since then been named Fabric, is being enhanced via the Hyperledger Consortium set up under the auspices of the Linux Foundation. Other efforts in the industry include Enterprise Ethereum, R3 Corda and BigchainDB.
J. Alejandro F. Castellanos, D. Coll-Mayor, Jose Antonio Notholt
The diversity of energy prosumer types makes it difficult to create appropriate incentive mechanisms that satisfy both prosumers and energy system operators alike. Meanwhile, European energy suppliers buy Guarantees of Origin (GoO) which allow them to sell green energy at premium prices while in reality delivering grey energy to their customers. Blockchain technology has proven itself to be a robust paying system in which users transact money without the involvement of a third party. Blockchain tokens can be used to represent a unit of energy and, just as GoOs, be submitted to the market. This paper focuses on simulating marketplace using the Ethereum Blockchain and Smart Contracts, where prosumers can sell tokenized GoOs to consumers willing to subsidize renewable energy producers. Such markets bypass energy providers by allowing consumers to obtain tokenized GoOs directly from the producers, which in turn benefit directly from the earnings. Two market strategies where tokens are sold as GoOs have been simulated. In the Fix Price Strategy prosumers sell their tokens to the average GoO price of 2014. The Variable Price Strategy focuses on selling tokens at a price range defined by the difference between grey and green energy. The study finds that the Ethereum Blockchain is robust enough to functions as a platform for tokenized GoO trading. Simulation results have been compared and the results indicate that prosumers earn significantly more money by following the Variable Price Strategy.
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.
현재 많은 사람들이 주로 사용하는 모바일 메신저는 중앙 집중형 서버를 이용하고 있다. 서버를 거쳐서 전송되는 메시지 내용은 서버에 일정 시간 보관된다. 따라서 데이터를 보관한 서버가 해킹될 경우 저장된 데이터에 대한 안전이 보장되지 않는다. 기존의 모바일 메신저에서는 공격자에 의해, 혹은 내부자에 의해서 서버에 저장된 데이터가 유출될 경우 이에 따르는 데이터 위/변조, 프라이버시 침해 뿐만 아니라 서비스량이 많아질 경우 발생되는 서버 과부하에 따른 문제들이 빈번히 발생할 수 있다. 본 논문에서는 이러한 문제를 해결한 새로운 모바일 메신저를 제안한다. 제안하는 모바일 메신저는 Ethereum의 Whisper를 사용하여 서버를 사용하지 않고 메시지를 전송할 수 있으며 모바일 쿠폰의 관리 및 전송 기능까지 지원한다. 전송하는 모든 데이터는 암호화 전송됨으로써 데이터의 기밀성을 보장하고 디지털 서명을 통해 메시지에 대한 무결성 및 인증을 보장한다.
Innovation in Digital Healthcare Systems
Advanced Steganography and Watermarking Techniques
La sécurité des nombreuses applications utilisant les blockchains repose non seulement sur la façon dont sont construites les blockchains sous-jacentes, mais aussi sur les spécificités de l’application construite à l’aide des données stockées dans ces blockchains , ainsi que sur le comportement des entités participant à l’expansion de la blockchain . Dans cet article, nous nous intéresserons à ces différents niveaux de sécurité et nous les illustrerons en nous appuyant sur deux applications phares des blockchains : la crypto-monnaie bitcoin et l’ordinateur-monde d’Ethereum.
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.
Technologia blockchain jest uznawana za jedną z przelomowych technologii informatycznych naszych czasow. Ponad 8 letnia juz historia tej technologii lączy sie nierozerwalnie z historią cyfrowej waluty Bitcoin, stworzonej przez tajemniczego Satoshi Nakamoto. Od czasu, gdy pierwsi uzytkownicy podlączyli sie do sieci Bitcoin, nastąpila ewolucja w postrzeganiu samej technologii blockchain jako technologii bazowej, dającej sie zastosowac nie tylko do tworzenia innych niz Bitcoin kryptowalut. Istotne bylo takze pojawienie sie niezaleznej od Bitcoin sieci blockchain nazwanej Ethereum, zaprojektowanej przez 19 letniego Vitalika Buterina, ktora zaoferowala nowe mozliwości funkcjonalne - inteligentne kontrakty. Blockchain jaki znamy dzisiaj bardzo intensywnie i skutecznie wykorzystuje znane koncepty kryptograficzne takie jak jednokierunkowe funkcje haszujące, kryptografie asymetryczną czy znakowanie czasem. Mechanizmy konsensusu zawieranego automatycznie przez uczestnikow sieci blockchain eliminują potrzebe zaufanej trzeciej strony przy przetwarzaniu transakcji, a inteligentne kontrakty poszerzyly obszar zastosowan technologii blockchain daleko poza transfer kryptowalut. Przedsiebiorstwa i instytucje na calym świecie dostrzegly innowacyjny potencjal wynikający z unikalnych cech technologii blockchain i dzisiaj są juz na etapie usprawniania swoich procesow z wykorzystaniem tej technologii. Przytoczone przyklady zastosowan realnie wplywają takze na poprawe jakości zycia zwyklych ludzi.
Abstract Blockchains are distributed data structures that are used to achieve consensus in systems for cryptocurrencies (like Bitcoin) or smart contracts (like Ethereum). Although blockchains gained a lot of popularity recently, there are only few logic-based models for blockchains available. We introduce $\mathsf{BCL}$, a dynamic logic to reason about blockchain updates, and show that $\mathsf{BCL}$ is sound and complete with respect to a simple blockchain model.
Since the release of Satoshi Nakamoto’s breakthrough white paper in 2008, which preceded disruptive peer to peer value transmission through the Bitcoin network instead of by traditional means, many applications have been sought in financial services generally and more narrowly within capital markets for the Blockchain technology that underpins the Bitcoin network. To date, no capital markets infrastructure globally has implemented a commercially viable Blockchain or distributed ledger technology (DLT) solution. Blockchain technology is also experiencing a period of inflated expectations on a global scale from being a solution to curbing online piracy to replacing rational databases. Within the ambit of capital markets, the most ‘obvious’ of all the use cases, is in post-trade securities settlement. There are various use-case specific prototypes at custodians, investment banks, stock exchanges and central securities depositories (CSDs) alike. The utopic use-case being the ability for a buyer (investor) to transact directly with a seller on a ‘peer to peer’ basis and to have settlement occur in near-immediate time with a low transaction cost and records of the transaction immediately available to the issuer of the stock, even on a crossborder basis. Although public blockchains such as the Bitcoin Blockchain and Ethereum provide the closest match to this elementary example, both have limitations and have experienced cyber security attacks, which have cast doubt over their ability to house or operate notoriously risk-averse capital markets infrastructures. Most of these infrastructures, although largely aligned to international best practices, are designed specifically to suit country or regional specific operations and regulations. This paper will review the approaches, solutions and cryptographic techniques taken to settle securities on a DLT platform to date and why none of these approaches have as yet resulted in commercial use either by an unknown business outside of the capital markets in a disruptive manner or by the incumbents. The approaches and the technology aspects will be combined to develop a conceptual DLT ecosystem for securities settlement. This will be based on available literature that could realistically be applied to a capital markets infrastructure and deliver some of the promises of DLT, which will potentially enhance securities settlement for the purposes of commercial use.
A. Pinar Ozisik, George Bissias, Brian Neil Levine
We make several contributions that quantify the real-time hash rate and therefore the consensus of a blockchain. We show that by using only the hash value of blocks, we can estimate and measure the hash rate of all miners or individual miners, with quanti able accuracy. We apply our techniques to the Ethereum and Bitcoin blockchains; our solution applies to any proof-of-work-based blockchain that relies on a numeric target for the validation of blocks. We also show that if miners regularly broadcast status reports of their partial proof-of- work, the hash rate estimates are signi cantly more accurate at a cost of slightly higher bandwidth. Whether using only the blockchain, or the additional information in status reports, merchants can use our techniques to quantify in real-time the threat of double-spend attacks.
Ioannis Kounelis, Gary Steri, Raimondo Giuliani, Dimitrios Geneiatakis · 6 authors
Micro-generation promises to greatly contribute to the energy balance of the energy grid; however, so far, its market penetration is going slow due to the few, or not-existing, direct economic benefits end-users would enjoy by deploying an in-house micro-generation system. In this paper, taking advantage of the potentialities of blockchain technologies, we propose a solar energy production and distribution architecture using smart contracts, a particular distributed ledger paradigm, to support automatic energy exchanges and auctions, potentially enabling a new, open and more fruitful, under an end-user perspective, energy micro-generation market. We present the conceptual design of the approach, as well the energy grid prototype and the control layer, running on the Ethereum platform. The proposed architecture has been implemented and validated through an in-house developed test-bed.
Robert Norvill, Beltrán Borja Fiz Pontiveros, Radu State, Irfan Awan · 5 authors
Smart contracts have recently attracted interest from diverse fields including law and finance. Ethereum in particular has grown rapidly to accommodate an entire ecosystem of contracts which run using its own crypto-currency. Smart contract developers can opt to verify their contracts so that any user can inspect and audit the code before executing the contract. However, the huge numbers of deployed smart contracts and the lack of supporting tools for the analysis of smart contracts makes it very challenging to get insights into this eco-environment, where code gets executed through transactions performing value transfer of a crypto-currency. We address this problem and report on the use of unsupervised clustering techniques and a seed set of verified contracts, in this work we propose a framework to group together similar contracts within the Ethereum network using only the contracts publicly available compiled code. We report qualitative and quantitative results on a dataset and provide the dataset and project code to the research community.
This paper conducts a performance analysis of two popular private blockchain platforms, Hyperledger Fabric and Ethereum (private deployment), to assess the performance and limitations of these state-of-the-art platforms. Blockchain, a decentralized transaction and data management technology, is said to be the technology that will have similar impacts as the Internet had on people's lives. Many industries have become interested in adopting blockchain in their IT systems, but scalability is an often- cited concern of current blockchain technology. Therefore, the goals of this preliminary performance analysis are twofold. First, a methodology for evaluating a blockchain platform is developed. Second, the analysis results are presented to inform practitioners in making decisions regarding adoption of blockchain technology in their IT systems. The experimental results, based on varying number of transactions, show that Hyperledger Fabric consistently outperforms Ethereum across all evaluation metrics which are execution time, latency and throughput. Additionally, both platforms are still not competitive with current database systems in term of performances in high workload scenarios.
Blockchain can be used to record transaction data and act as an encrypted and immutable digital history of anything from cryptocurrencies such as Bitcoin and Ethereum. This paper introduces blockchain technology, standardization, and its relationship with cloud computing. Also, it provides the considerations for blockchain as a service as a new standard.
This chapter looks beyond the novelty of self-executing ‘smart contracts’ in blockchain networks and explores developments against the background fact that commercial parties have, for centuries, used documentary credit to simulate autonomous performance. Blockchain-based smart contracts and documentary credit share three core functionalities which are essential to any effective autonomous performance, analogue or digital—they both (i) act through internalized media of exchange; (ii) operate as closed systems; and (iii) provide means of securing sufficient resources to guarantee contractual performance. Using these three functionalities as a framework, this chapter conducts a comparative analysis of mechanisms for effecting autonomous contractual performance in a commercial setting. From this comparison, a few hypotheses are drawn regarding the potential areas where smart contract technology is more likely to find fruitful application. In particular, the chapter considers potential limitations to applying smart contracts to scenarios beyond digital asset transfers, how dispute resolution mechanisms should be designed to complement (rather impair) the autonomous nature of contractual performance under smart contracts, and potential capital cost implications which might arise in some cases when parties seek to replace human intermediaries with smart contracts.
The National Taiwan University of Science and Technology is established as a worldclass
university of multifaceted excellence through international outreach and applied
research.
In order to make the university more efficient, concerned, adapt it to the use of new
technologies incoming and make it more innovative Professor Shuo-Yan Chou among
other professors came to the idea of creating a Smart Campus. This project involves
interdepartmental efforts, ideas and new technologies to reach the main goal.
Some of the projects concerning this Smart Campus are faced in developing apps to
report maintenance problems; others want to use new technologies such as machine
learning to facilitate the study of human flow; and other projects want to improve energy
consumption by monitoring the usage of water dispensers.
This particular project sought the objective of creating a rewarding system and a microeconomy
sharing society to be implemented in the smart campus. According to that,
applying the newest technologies is the key point.
For the past few years, the technology of blockchain has been in upswing. This
technology breaks with the centralized systems of nowadays to reach a decentralized
network with peer-to-peer communication. Furthermore, blockchain enables users to
create and use smart contracts that, among all of their characteristics, highlight the
possibility of the creation of a token/cryptocurrency to be exchanged.
After a deep research in blockchain, a first brief introduction to the main characteristics of
it is given to the reader. When the basic concepts of this revolutionary technology have
been achieved, it is time to apply blockchain to the rewarding system project.
To do so, a private network based on the Ethereum Platform has been created. This
network is sustained by a certain number of computers, working as nodes, that verify
transactions happening across the network. Once the blockchain is created, the project
goes through the creation of a token (named NTUSToken) that is given as a reward for
making some good practices and is interchangeable by the students, giving them the
sense of a micro-economy society based on the token. On this private blockchain, users
can create accounts, transfer tokens and check their balances.
Finally, the last key point of the project is to make this system handy and attractive to
users. As blockchain is not a trivial technology to understand, users have to be able to register, log in to their accounts and share tokens without the necessity of knowing the
technology behind it. For this purpose, a browser application connected to the private
network has been created. With this application, users have an easy platform to join the
micro-economy.
By now, the implementation of a micro-economy and a rewarding system in the NTUST
has been achieved and can be implemented by following this thesis.
Some of the codes and files used are shown and detailed in the Annex.
Most blockchain systems are forkable in that they require participants to agree on a chain out of multiple possible branches of blocks. In this paper, we identify a new form of attack, called the Balance attack, against these forkable blockchain systems. The novelty of this attack consists of delaying network communications between multiple subgroups of nodes with balanced mining power. Our theoretical analysis captures the tradeoff between the network delay and the mining power of the attacker needed to double-spend in the GHOST protocol with high probability. We quantify our analysis in the settings of the Ethereum testnet of the R3 consortium where we show that a single machine needs to delay messages for 20 minutes to double spend while a coalition with a third of the mining power would simply need 4 minutes to double spend with 94% of success. We experiment the attack in our private Ethereum chain before arguing for a non-forkable blockchain design to protect against Balance attacks.
The advent of Bitcoin was just the start of something big. Now Ethereum takes this technological advance to the next level. Kate Timmerman and Molly Thomas from The Legal Forecast explain.
In the absence to date of any specific pre-emptive federal regulation of blockchain distributed ledger technology in fintech, smart contracts, or other uses, this paper discusses early state legislation including Arizona, California, Delaware, Hawaii, Illinois, Maine, New York, Nevada and Vermont. While the list comprises usual suspects for early adoption of disruptive technology regulation, especially of its real-time aspects that were recognized in In re Dole Food Co (Del. Ch. Feb. 15, 2017), the mechanics of blockchain are still evolving and restrictive regulations appear both premature and at risk of expedited obsolescence. Before expanding to general record-keeping transactions, blockchain was first used in bitcoin, a virtual currency. Then, blockchain evolved towards self-executing smart contracts using ethereum technology and may eventually reach an “Internet of Agreements.” While its promise for applications like virtual currencies and payments is obvious and vigorously explored by major financial institutions, blockchain’s real strength lies in authentication and keeping records up-to-date, especially for valuable, highly liquid assets like securities. Key developments for blockchain’s regulation and implementation in an evidentiary context occurred in Arizona (recognition of smart contracts), Vermont (blockchain as evidence), Chicago (real estate records), and, most importantly, Delaware (pending initiative authorizing registration of shares of Delaware companies in blockchain form). Since 64 percent of Fortune 500 companies and over 1 million entities are incorporated in Delaware, an enactment of Delaware’s initiative will change regulatory landscape for securities by setting precedent in the most important corporate jurisdiction of the U.S. Other states competing for corporate taxes and fees would be sure to follow.