Michał Król, Alberto Sonnino, Mustafa Al-Bassam, Argyrios G. Tasiopoulos · 6 authors
As cryptographic tokens and altcoins are increasingly being built to serve as utility tokens, the notion of useful work consensus protocols is becoming ever more important. With useful work consensus protocols, users get rewards after they have carried out some specific tasks useful for the network. While in some cases the proof of some utility or service can be provided, the majority of tasks are impossible to verify reliably. To deal with such cases, we design “Proof-of-Prestige” (PoP)—a reward system that can run directly on Proof-of-Stake (PoS) blockchains or as a smart contract on top of Proof-of-Work (PoW) blockchains. PoP introduces “prestige,” which is a volatile resource that, in contrast to coins, regenerates over time. Prestige can be gained by performing useful work, spent when benefiting from services, and directly translates to users minting power. Our scheme allows us to reliably reward decentralized workers while keeping the system free for the end-users. PoP is resistant against Sybil and collusion attacks and can be used with a vast range of unverifiable tasks. We build a simulator to assess the cryptoeconomic behavior of the system and deploy a full prototype of a content dissemination platform rewarding its participants. We implement the blockchain component on both Ethereum (PoW) and Cosmos (PoS), provide a mobile application, and connect it with our scheme with a negligible memory footprint. Finally, we adapt a fair exchange protocol allowing us to atomically exchange files for rewards also in scenarios where not all the parties have Internet connectivity. Our evaluation shows that even for large Ethereum traces, PoP introduces sub-millisecond computational overhead for miners in Cosmos and less than 0.013$ smart contract invocation cost for users in Ethereum.
Sina Rafati Niya, Eryk Schiller, Ile Cepilov, Fabio Maddaloni · 8 authors
Proof-of-Work (PoW) in Blockchains (BC), which is a widely used consensus algorithm, suffers from high power consumption of miners and low transaction rates. This work demonstrates a Proof-of-Stake (PoS)-based BC called Bazo, which is specially designed and adapted for Internet of Things (IoT) data streams. Bazo displays enhanced performance in terms of energy consumption and transactions processing in comparison to PoW-based BC. To further improve performance of Bazo, sharding and transaction aggregation methods are employed. Moreover, IoT-BC adaptation helpers of a modular and layered architecture are provided to allow wireless devices to submit data into the BC. The designed architecture can support multiple hardware and software platforms as well as network technologies.
Peter Robinson, Raghavendra Ramesh, Sandra Johnson
Public blockchains such as Ethereum and Bitcoin do not give enterprises the privacy they need for many of their business processes. Consequently consortiums are exploring private blockchains to keep their membership and transactions private. Ethereum Private Sidechains is a private blockchain technology which allows many blockchains to be operated in parallel. Communication is needed between Ethereum Private Sidechains to allow a function in a contract on one sidechain to execute function calls which return values from, or update the state of, another sidechain. We propose a crosschain technique which allows transactions to be executed atomically across sidechains, introduce a new mechanism for proving values across sidechains, describe a transaction locking mechanism which works in the context of blockchain to enable atomic transactions, and a methodology for providing a global time-out across sidechains. We outline the programming model to be used with this technology and provide as an example, a variable amount atomic swap contract for exchanging value between sidechains. Although this paper presents Atomic Crosschain Transaction technology in the context of Ethereum Private Sidechains, we discuss how this technology can be readily applied to many blockchain systems to provide cross-blockchain transactions.
About 1Bn people around the globe are born and live without identity documents. In addition, displaced people, projected at 1Bn within a generation, often find themselves without worthy identity documentation even if they had any in their country of origin.
Given that centralized, top-down identity-granting solutions are failing a large portion of the world population, a bottom-up, grassroots, decentralized solution that allows every human being to create and own a trustworthy \emph{genuine global identity} is an urgent necessity. Such a bottom-up solution is worthy only if it is resilient to malicious antagonists that create fake and duplicate identities (so called \emph{sybils}). Furthermore, for a solution to be truly grassroots, the people that rely on it for their global identity should also be its sovereign. Hence its governance has to be sybil-resilient as well.
Here, we present a foundation for a decentralized, grassroots, bottom-up, self-sovereign process in which every human being may easily create and own a genuine global identity, realized as a public key. The solution relies on the formation of a Web of Trust among global identities, but does not rely on biometrics, nor does it require to store any personal information on public or even third-party storage, except for the public key itself. The approach is designed for natural realization using distributed ledger/blockchain technology. For the solution to be complete, additional components are needed, including a mechanism that encourages honest behavior and an egalitarian cryptocurrency to fuel the mechanism. These are a subject for future research.
Cryptocurrencies came to the world in the recent decade and attempted to offer a new order where the financial system is not governed by a centralized entity, and where you have complete control over your account without the need to trust strangers (governments and banks above all). However, cryptocurrency systems face many challenges that prevent them from being used as an everyday coin. In this paper we attempt to take one step forward by introducing a cryptocurrency system that has many important properties. Perhaps the most revolutionary property is its deterministic operation over a fully asynchronous communication network, which has sometimes been mistakenly considered to be impossible. By avoiding any temporal assumptions, we get a system that is robust against arbitrary delays in the network, and whose latency is only a function of the actual communication delay. The presented system is based on familiar concepts $-$ banking and democracy. Our banks, just like normal banks, keep their clients' money and perform their clients' requests. However, because of the cryptographic scheme, your bank cannot do anything in your account without your permission and its entire operation is transparent so you don't have to trust it blindly. The democracy means that every operation performed by the banks (e.g., committing a client transaction) has to be accepted by a majority of the coin holders, in a way that resembles representative democracy where the banks are the representatives and where each client implicitly delegates his voting power (the sum of money in his account) to his bank. A client can switch banks at any moment, by simply applying a corresponding request to the new bank of his choice.
The main goal of this article is to present a direct approach for the formula giving the long-term apparent hashrates of Selfish Mining strategies using only elementary probabilities and combinatorics, more precisely, Dyck words. We can avoid computing stationary probabilities on Markov chain, nor stopping times for Poisson processes as in previous analysis. We do apply these techniques to other block withholding strategies in Bitcoin, and then, we consider also selfish mining in Ethereum.
With the rising demands from customers and users and the development of ever advanced technologies, many space missions nowadays require more than one satellite to fulfill their mission objectives. Although replacing single satellite systems (SSSs) by multiple satellite systems (MSSs) offers advantages, such as enhanced spatial and temporal coverage as well as high robustness and multifunctional purposes, it also introduces new challenges. There is no doubt that as the number of satellites in a mission grows, the complexity and operation cost of controlling and coordinating these satellites only by human (or ground based) operators will increase dramatically. In addition, for some deep space missions or complex operational tasks, due to the long signal transmission time between the spacecraft and ground-based antennas or short communication windows, there will not be enough time or resources for operators to sufficiently and efficiently control all of the required onboard functions from mission control centers. Therefore, to enhance the efficiency of operating an MSS, and to reduce the cost of human resources and ground infrastructure, an onboard autonomous system (OAS) for MSS is a promising solution. For specific missions, the use of an OAS may even be a mission enabler. One important function of an OAS is to provide planning and re-planning services based on different mission requirements. The objective of this research is to develop and characterize onboard autonomous mission planning and re-planning approaches for MSSs. Traditional planning approaches have been reviewed and proven to be inappropriate and inefficient for complex planning problems in the harsh space environment when severe system constraints are enforced and a large number of vehicles constitutes the MSS. % Artificial intelligence (AI) approaches, in contrast, are more suitable for complex problems due to their broad adaptability and their ability to cope with large-scale variables. To overcome these deficiencies, engineers and researchers have started to develop OAS with the help of Artificial Intelligence (AI) techniques to allow for more complex space missions. Based on the relevance of this problem, the following research questions (RQs) have been formulated and will be answered in this thesis. % and a review of the state-of-the-art scientific literature \\textbf{RQ1: What are the strengths of using AI in space missions? How to use a centralized AI algorithm in a multi-satellite system to decompose mission objectives and perform mission planning for the entire system?} \\textbf{RQ2: How to define emergency situations which may occur during mission operations? How to use AI algorithms to handle mission re-planning and re-scheduling problems?} \\textbf{RQ3: How to design cooperation and negotiation approaches for an MSS to reach an agreement? How to improve AI algorithms for distributed onboard mission planning problems?} To define potential scenarios, a reference mission is introduced in this thesis, called \\textit{Discovering the Sky at the Longest Wavelength (DSL)}. The mission is assumed to comprise one Mother Satellite (MS) and eight Daughter Satellites (DSs) in a lunar orbit. Its scientific objective is to observe the universe in the hitherto-unexplored very low frequency (below 30 MHz) electromagnetic spectrum. The DSs collect scientific data only in those parts of the orbit which is shielded from radio frequencies emitted by the Earth. These DSs can only transmit collected data to the MS when they are outside of this shielded orbit sections, to prevent interferences caused by communication. % The DSs collect scientific data and transmit those to the MS with the constraints what scientific data collection may only occur in the part of the orbit. This part of the orbit is shielded from radio frequencies emitted by the Earth and no other DSs are transmitting data to the MS. This renders mission operations of DSL very complex. The existing body of knowledge on mission planning problems for multi-satellite systems is reviewed. It comprises three categories: classical approaches, heuristic approaches, and advanced techniques (e.g., team negotiation mechanisms, evaluation algorithms). Targeting the complexity of foreseeable DSL planning problems, nine representative optimization algorithms are applied to fourteen test functions. The results indicate that Evolutionary Algorithms (EAs) have a broader adaptability than classical approaches. They are also more efficient than other heuristic approaches. Therefore, EAs family is selected as suitable candidate for the reference MSS. % fourteen test functions are used to test nine representative algorithms to provide a preliminary selection for the reference MSS.=-098 % The fourteen test functions we used contain different types of objective functions and constraints to guarantee the diversity of the preliminary selection. % The goal of this selection is to identify a suitable approach for an MSS to handle different types of optimization problems. Eight constrained and six unconstrained test functions are employed as benchmarks. The operations concept of the DSL mission foresees that the initial mission planning is performed by the MS, while the eight DSs are preliminary executing data collection and transmission tasks. % Considering the scientific design of the DSL mission, the initial mission planning procedures are all performed by the Mother Satellite (MS), while the rest eight Daughter Satellites (DSs) are just participating satellites which response for gathering and transmitting data. During this phase, the MSS implements a centralized architecture and the MS conducts a centralized planning approach. By comparing basic Genetic Algorithm (GA) with several state-of-the-art improved GAs, its weaknesses are revealed. In this thesis, to overcome early and slow convergence problems, the need to develop a new mutation strategy for GA is motivated. % By revealing the weaknesses of the basic Genetic Algorithm (GA), along with a comparison with several other improved GAs, The proposed novel mutation strategy is called Hybrid Dynamic Mutation (HDM), which contains a standard mutation operator and an escape mutation operator. While the standard mutation operator uses a small mutation rate for approaching the global optimum, the escape mutation operator uses a larger mutation rate to allow an escape from local optima. The simulation results indicate that the proposed HDM can improve the basic GA (which turns into the HDMGA) leading to a superior performance on correctness and effectiveness as compared to alternative GAs. Based on these findings, AI related methods are considered a promising category as compared to classical methods due to their flexibility and effectiveness to support the onboard planning for an MSS. In addition, the proposed HDMGA also provides a satisfying result for the considered initial mission planning problems. Internal or external causes, e.g. an actuator failure or the challenging space environment, can lead to a satellite malfunction during mission operations. This thesis considers the two most important behaviors of the DSL mission, observation and communication, and proposes potential emergency scenarios to handle possible system failures on DSs. Two re-planning methods, one called the Cyclically Re-planning Method (CRM), the other one the Near Real-time Re-planning Method (NRRM), are established and compared. The CRM performs re-planning at the beginning of each orbit and only re-plans for one orbit. The NRRM performs re-planning in a near real-time setting when the emergency occurs. Its re-planning covers for the rest of the mission. Three simulation study cases are formulated based on assumed emergency scenarios. % Each case is designed to represent a different level of failures on multiple DSs. The proposed two methods are compared on three aspects: the total number of data observed from all DSs within a certain time frame, the total number of data the MS received from all DSs within a certain time frame, and the average computation time needed for re-planning. The results indicate that: (1) The NRRM allows to observe and transmit more data than the CRM within a specific operational lifetime. (2) The NRRM requires more computational time than the CRM for emergency situations, while it requires less time than the CRM for nominal situations. % For emergency situations, the CRM can therefore provide re-planning sequences faster than the NRRM, while for nominal operations, the NRRM is much faster than the CRM. This research also covers a much more severe scenario, namely that the MS becomes fully non-functional in an emergency situation. This would render the MS unable to provide mission planning and re-planning services for the MSS. Without its main controller on the MS, all DSs now need to cooperate to jointly solve the mission planning problems. Due to the loss of the MS, both distributed and decentralized architectures, which the MSS could then use are introduced. In a distributed architecture, each DS is connected with all other DSs directly or through DS which acts as retranslator. In a decentralized architecture, each DS can only communicate with its neighbors. Considering that the mission allocation problems in different organizational architectures are similar to information games in game theory, a game-theoretical model of the Multi-Satellite Mission Allocation (MSMA) problem is formulated. % Three new negotiation mechanisms are introduced, compared and analyzed in theoretical terms. The Utility-based Regret Play (URP) negotiation mechanism is proposed for an MSMA problem using a distributed architecture. It inherits the ability to evaluate individual utility at each negotiation step from the Utility-based Fictitious Play, and the ability to regret the current choice and for not proposing particular choices in the past negotiation steps from the Regret Matching
Jason A. Tran, Gowri Ramachandran, Palash M Shah, Claudiu Danilov · 6 authors
Blockchain technology has the potential to disrupt applications beyond cryptocurrencies. This work applies the concepts of blockchain technology to swarm robotics applications. Swarm robots typically operate in a distributed fashion, wherein the collaboration and coordination between the robots are essential to accomplishing the application goals. However, robot swarms may experience network partitions either due to navigational and communication challenges or in order to perform certain tasks efficiently. We propose a novel protocol, SwarmDAG, that enables the maintenance of a distributed ledger based on the concept of extended virtual synchrony while managing and tolerating network partitions.
Since the inception of Bitcoin, cryptocurrencies and the underlying blockchain technology have attracted an increasing interest from both academia and industry. Among various core components, consensus protocol is the defining technology behind the security and performance of blockchain. From incremental modifications of Nakamoto consensus protocol to innovative alternative consensus mechanisms, many consensus protocols have been proposed to improve the performance of the blockchain network itself or to accommodate other specific application needs. In this survey, we present a comprehensive review and analysis on the state-of-the-art blockchain consensus protocols. To facilitate the discussion of our analysis, we first introduce the key definitions and relevant results in the classic theory of fault tolerance which help to lay the foundation for further discussion. We identify five core components of a blockchain consensus protocol, namely, block proposal, block validation, information propagation, block finalization, and incentive mechanism. A wide spectrum of blockchain consensus protocols are then carefully reviewed accompanied by algorithmic abstractions and vulnerability analyses. The surveyed consensus protocols are analyzed using the five-component framework and compared with respect to different performance metrics. These analyses and comparisons provide us new insights in the fundamental differences of various proposals in terms of their suitable application scenarios, key assumptions, expected fault tolerance, scalability, drawbacks and trade-offs. We believe this survey will provide blockchain developers and researchers a comprehensive view on the state-of-the-art consensus protocols and facilitate the process of designing future protocols.
In this paper, we analyse the foundations of Blockchain and DAG Directed acyclic graph its evolution and the tangle, DAG try to solve the most issues in blockchain and make a system that stable for Internet-of Things (IOT) industry. In addition, to before that we need to monition Distributed ledger technology (DLT) since DLT rely on blockchain in Bitcoin and Ethereum we have this kind of issues. DAG it has special techniques from other cryptocurrencies and using different methods.
Krishnendu Chatterjee, Amir Kafshdar Goharshady, Arash Pourdamghani
In today's cryptocurrencies, Hashcash proof of work is the most commonly-adopted approach to mining. In Hashcash, when a miner decides to add a block to the chain, she has to solve the difficult computational puzzle of inverting a hash function. While Hashcash has been successfully adopted in both Bitcoin and Ethereum, it has attracted significant and harsh criticism due to its massive waste of electricity, its carbon footprint and environmental effects, and the inherent lack of usefulness in inverting a hash function. Various other mining protocols have been suggested, including proof of stake, in which a miner's chance of adding the next block is proportional to her current balance. However, such protocols lead to a higher entry cost for new miners who might not still have any stake in the cryptocurrency, and can in the worst case lead to an oligopoly, where the rich have complete control over mining.
Increased interest in scalable and high-throughput blockchains has led to an explosion in the number of committee selection methods in the literature. Committee selection mechanisms allow consensus protocols to safely select a committee, or a small subset of validators that is permitted to vote and verify a block of transactions, in a distributed ledger. There are many such mechanisms, each with substantially different methodologies and guarantees on communication complexity, resource usage, and fairness. In this paper, we illustrate that, despite these implementation-level differences, there are strong statistical similarities between committee selection mechanisms. We concretely show this by proving that the committee selection of the Avalanche consensus protocol can be used to choose committees in the Stellar Consensus Protocol that satisfy the necessary and sufficient conditions for Byzantine agreement. We also verify these claims using simulations and numerically observe sharp phase transitions as a function of protocol parameters. Our results suggest the existence of a "statistical taxonomy" of committee selection mechanisms in distributed consensus algorithms.
Annotation: This Master's thesis provides a comprehensive analysis of various consensus mechanisms essential for distributed ledger technologies like blockchain, sidechain, DAG, and more. A total of 22 consensus mechanisms, including traditional and alternative proof-based algorithms, fault tolerance algorithms, and DAG-based algorithms, were evaluated using eight criteria such as security, decentralization, scalability, and energy efficiency. The study includes an extensive set of testing scenarios for these mechanisms, and recommendations are given based on the analysis of individual mechanisms, emphasizing the importance of choosing mechanisms suited to specific system requirements. The research contributes significantly to the field by providing a detailed understanding of consensus mechanisms, a comparative analysis highlighting their strengths and weaknesses, and valuable test scenarios for future studies.
In cloud computing, data is duplicated to prevent data loss. One way to achieve data consistency in such a distributed computing systems is to use a blockchain. Based on practical Byzantine fault tolerance (PBFT), a specific type of blockchain, this paper proposes a synchronous Byzantine fault tolerance (SBFT) algorithm that not only maintains data consistency, but also has much higher efficiency than other general blockchain algorithms. We provide experimental results that demonstrate the algorithm's data consistency, efficiency, and reliability.
The blockchain technology is more and more important in computer security. The core of the blockchain system is consensus. However, many consensus mechanisms reward those groups that own the majority of the resources. In addition, the performance of these consensus mechanisms is poor. In this paper we first present Proof of Value (POV), an incentive mechanism that rewards the value creators. With the help of POV, we reward the user who creates value and control the number of coins through the incentive coefficient adjustment algorithm. To improve the performance of POV in permissioned blockchain, we designed Hypernet, an off-chain transaction system. By designing the transaction system Hy-pernet, the transaction can be handled without blockchain. Finally, we evaluate our system by generating random parameters to invoke the contract. Then we record the real time for issuing the rewards. The test results show that the loss of the system is about 2% when the POV is added. The performance of the Hypernet is four times higher than the traditional permissioned blockchain transaction system.
Blockchain has gained much attention in recent academic and research works not only in crypto-currency but also in many other fields such as supply chain, health, storage etc. The application of blockchain in data management domain, however, is mostly geared towards the aspect of security and immutability. In this paper we propose integrating blockchain with distributed data management and study some open challenges and assumptions in doing so. We claim that, from data management perspective, blockchain's ability to handle unequal participants is more important than security and immutability. Finally, we propose possible ideas to integrate blockchain into distributed data transaction and management workflows to design a globally consistent data store ensuring availability guarantees along with support for unifying heterogeneous data backends.
Mauro C. Argañaraz, Mario Berón, Miguel Alfredo Bustos, Pedro Rangel Henriques · 5 authors
Ethereum es el principal ecosistema basado en blockchain que proporciona un entorno para codificar y ejecutar contratos inteligentes, propiedad que en estos últimos años recibió gran atención por las nuevas aplicaciones comerciales y, también, por la comunidad científica. El proceso de escritura de contratos seguros y de buen desempeño en la plataforma Ethereum es un gran desafío para los desarrolladores. Implica la aplicación de paradigmas de programación no convencionales debido a las características inherentes de la ejecución de programas de computación distribuida. Además, los errores en los contratos desplegados pueden tener graves consecuencias debido al acoplamiento inmediato del código del contrato y las transacciones financieras. El manejo directo de los activos significa que las fallas tienen más probabilidades de ser relevantes para la seguridad y tienen mayores consecuencias económicas que los errores en las aplicaciones típicas. Una serie de reportes de incidentes muestran que los problemas de seguridad se han utilizado con propósitos fraudulentos. En este artículo, se describe una línea de investigación que se enfoca en fortalecer los aspectos de seguridad, basado en una base sólida de diseño, patrones de código establecidos y probados que faciliten el proceso de escritura de código funcional y libre de errores, para proporcionar una herramienta que permita analizar y detectar falencias de manera automática.
Blockchain technology is considered to be one of the most thriving future Internet technologies with the potential to have a great impact not only on the technical aspects of our lives but also on the social, economic, juristic, security and on many more aspects. Since the appearance of a Bitcoin as the most popular Blockchain based currency a decade ago, the possibilities and strengths of the Blockchain technology have been investigated a lot. The Blockchain technology has a dozen of use cases in different areas of life, whereby one of the most important is Internet of Things and Internet of Everything. This paper concentrates on the vulnerabilities of Blockchain technology, especially on the problem of Byzantine Fault Tolerance. It is one of the crucial problems of Distributed Ledger Technologies in general. Other vulnerabilities of the Blockchain technology analyzed in this paper include the partition and delay attacks.
While cryptocurrencies and blockchain applications continue to gain popularity, their energy cost is evidently becoming unsustainable. In most instances, the main cost comes from the required amount of energy for the Proof-of-Work, and this cost is inherent to the design. In addition, useless costs from discarded work (e.g., the so-called Forks) and lack of scalability (in number of users and in rapid transactions) limit their practical effectiveness. In this paper, we present an innovative scheme which eliminates the nonce and thus the burden of the Proof-of-Work which is the main cause of the energy waste in cryptocurrencies such as Bitcoin. We prove that our scheme guarantees a tunable and bounded average number of simultaneous mining whatever the size of the population in competition, thus by making the use of nonce-based techniques unnecessary, achieves scalability without the cost of consuming a large volume of energy. The technique used in the proof of our scheme is based on the analogy of the analysis of a green leader election. The additional difference with Proof-of-Work schemes (beyond the suppression of the nonce field that is triggering most of the waste), is the introduction of “empty blocks” which aim are to call regular blocks following a staircase set of values. Our scheme reduces the risk of Forks and provides tunable scalability for the number of users and the speed of block generation.
Bitcoin is the world's most successful digital currency. It uses a public distributed ledger called the blockchain to maintain the transaction history in the network. It employs a Proof-of-Work (PoW) protocol for miners to add more blocks of transactions to the chain in order to arrive at a consensus of the state of the network. Due to the nature of the consensus mechanism used, miners are not given any sense of their progression when solving a PoW problem. The only strategy presented to them is a brute-force search where it is unknown to them how far away they or other miners are to a solution, and if the problem is worth dedicating further resources to. This results in a slow and highly energy inefficient consensus protocol. In this paper we present an alternative PoW mechanism which introduces the idea of progression when solving such puzzles. This Alt-PoW mechanism gives participants a network view of how all other miners are faring in the block finding process, so they can decide whether it is in their interest to withdraw from a block race or to continue dedicating their resources towards it. We also present a mechanism to allow for multiple interconnected chains as opposed to a single blockchain, so that block finding can be parallelized. Participants can decide which chain to dedicated their resources to, based on which has the best chance of them being successful mining on at any particular time. We show that this results in a faster and more energy efficient protocol.
IOTA cryptocurrency is a distributed solution for secure messaging and micropayments between Internet-of Things devices. The authors introduced open source hardware accelerators for Curl hash function and proof-of-work computations to increase the processing rate of IOTA transactions. The structure and operation principle of both accelerators are described. Proposed accelerators have been implemented on FPGA and integrated into ARM-based System-on-Chip. The characteristics of the system have been evaluated. Compared to official software implementation the proposed hardware accelerators demonstrate x2100 speed up on the creation of IOTA transactions.
Distributed Ledger Technologies and particularly Blockchain-based Decentralized Applications entail transaction data from various use cases and usage behaviors in a decentralized manner. In this context, we propose to apply Process Mining as a means to understand and quantify how a Distributed Ledger is de facto utilized. This paper introduces a heuristic Process Mining approach for extracting high level process structures from Distributed Ledgers and Decentralized Applications, which can also represent changes over time. The universal approach is demonstrated on the basis of the complete set of all transactions that happened on the Ethereum Blockchain during its first three years. Events, cases, and activities allow to compile an evolutionary time line, which shows the Blockchain evolving from its early stages to broader adoption. Furthermore, measures of activity significance, confidence, and process complexity are used to compile dependency graphs, which represent process transitions.
The Bitcoin blockchain is a secure, distributed ledger that enables trusted transactions across untrusted entities. However, many applications need much faster transaction confirmation than that of the current Bitcoin blockchain. In this paper, we present a high-throughput, low-latency, deterministic confirmation mechanism called ACCEL for accelerating Bitcoin's block confirmation mechanism. Our key idea for achieving faster confirmation is the quick identification of singular blocks that provably belong to the blockchain. While it is impossible to determine with certainty if a block belongs to a blockchain when network delays are unbounded, singular block detection exploits the fact that the end-to-end latency between Bitcoin miners is substantially lower than the inter-block spacing and can be assumed to be upper bounded. ACCEL is especially suitable for low-latency, permissioned blockchains, where the block spacing can be optimized to the blockchain's small latencies to greatly improve throughput. We evaluate ACCEL's performance with extensive simulations and with a real implementation built with minimal changes to and fully compatible with the Bitcoin blockchain. We show that with appropriate bounds on the end-to-end latency, it is possible to reduce transaction confirmation latencies to milliseconds with ACCEL, and so meet the performance needs of a wide range of applications.
Samia El Haddouti, Mohamed Dâfir Ech-Cherif El Kettani
The emergence of Blockchain technology as the biggest innovations of the 21stcentury, has given rise to new concepts of Identity Management to deal with the privacy and security challenges on the one hand, and to enhance the decentralization and user control in transactions on Blockchain infrastructures on the other hand. This paper investigates and gives analysis of the most popular Identity Management Systems using Blockchain: uPort, Sovrin, and ShoCard. It then evaluates them under a set of features of digital identity that characterizes the successful of an Identity Management solution. The result of the comparative analysis is presented in a concise way to allow readers to find out easily which systems satisfy what requirements in order to select the appropriate one to fit into a specific scenario.