We propose a novel model for teaching and learning called Decentralized Autonomous Education (DAE for short). DAE exploits the dual principles of freedom and responsibility, meritocracy and inclusivity, privacy and transparency in the educational process. It also fits well the philosophy of blockchain technology, and more generally of Web3 – the third iteration of the World Wide Web – specifically the tenets of decentralization, disintermediation, incentive and sovereignty of the individual. In this paper, we fully illustrate the DAE model, highlighting the theoretical and practical links between DAE and Web3, dissecting the pros and cons of the proposed learning method and reviewing related pedagogical approaches. Finally, we describe the front-end and back-end design of the DAE app, a decentralized application that implements the DAE learning model.
As a distributed ledger technology, blockchain can be used in the fields of information sharing, logistics chain, certificate storage and anti-counterfeiting. However, due to the isolated nature of the blockchain network and the high degree of heterogeneity between chains, the connection between different chains is hindered, which makes each blockchain form a value island and cannot serve the practical applications well. The emergence of cross chain technology realizes the value circulation between different chains and enhances the interoperability and scalability of blockchains. Among them, the cross-chain technology of notary mechanism transforms the trust problem among cross-chain users into the loyalty problem of notary, and is favored for its ability to support different types of underlying blockchain systems in a more flexible manner. However, the introduction of notaries in the notary mechanism also leads to the risk of centralization, and the loyalty of notaries will directly determine the success of cross-chain transactions. In this paper, by introducing the improved PageRank algorithm, we design a dynamic notary group election mechanism based on reputation value, which effectively avoids malicious nodes from becoming notaries and improves the success rate of cross-chain transactions while preventing the over-concentration of rights in a single node. The experimental analysis shows that selecting notary representatives by dynamically adjusting the reputation value ranking of notary nodes increases the selection probability of loyal nodes, which is more reasonable than the method of randomly selecting notaries.
Alexis Asseman, Tomasz Kornuta, Patel, Anirudh, Matt Deible · 5 authors
The Graph Protocol indexes historical blockchain transaction data and makes it available for querying. As the protocol is decentralized, there are many independent Indexers that index and compete with each other for serving queries to the Consumers. One dimension along which Indexers compete is pricing. In this paper, we propose a bandit-based algorithm for maximization of Indexers' revenue via Consumer budget discovery. We present the design and the considerations we had to make for a dynamic pricing algorithm being used by multiple agents simultaneously. We discuss the results achieved by our dynamic pricing bandits both in simulation and deployed into production on one of the Indexers operating on Ethereum. We have open-sourced both the simulation framework and tools we created, which other Indexers have since started to adapt into their own workflows.
Lu Han, Renchao Xie, Yuzheng Ren, F. Richard Yu · 5 authors
As a recently proposed network architecture, the computing power network (CPN) combines the ability of end, edge, cloud computing, and transmission network to realize the flexible and efficient scheduling and transaction of ubiquitous multi-resources, such as computing, cache, communications, and intelligent models. However, in CPN, multi-resources are deployed in a distributed manner. So, efficient, reliable and distributed resource transaction solutions are sought. Therefore, in this paper, we propose a non-fungible token (NFT)-based resource transaction scheme for CPN. We use NFT to tokenize and describe multi-resources by metadata to enable applications to network multi-resources efficiently and ensure transaction se-curity. Also, we formulate the trading utility of sellers and buyers and present a trusted trading process. To improve the system efficiency by increasing the matching success rate and simplify the complexity of combinatorial resources matching, we design the decision and pricing policy by distributed double auction mechanism. Simulation results demonstrate the effectiveness of the proposed scheme.
Sahar Salimpour, Farhad Keramat, Jorge Peña Queralta, Tomi Westerlund
Multiple opportunities lie at the intersection of multi-robot systems and distributed ledger technologies (DLTs). In this work, we investigate the potential of new DLT solutions such as IOTA, for detecting anomalies and byzantine agents in multi-robot systems in a decentralized manner. Traditional blockchain approaches are not applicable to real-world networked and decentralized robotic systems where connectivity conditions are not ideal. To address this, we leverage recent advances in partition-tolerant and byzantine-tolerant collaborative decision-making processes with IOTA smart contracts. We show how our work in vision-based anomaly and change detection can be applied to detecting byzantine agents within multiple robots operating in the same environment. We show that IOTA smart contracts add a low computational overhead while allowing to build trust within the multi-robot system. The proposed approach effectively enables byzantine robot detection based on the comparison of images submitted by the different robots and detection of anomalies and changes between them.
Yunming Xiao, Sarit Markovich, Aleksandar Kuzmanovic
Having enabled numerous applications, blockchains have attracted not only much attention, in the past decade, but also huge amount of resources: talent, capital, energy, etc. Focusing on the mining side of the market, in this paper, we aim at understanding how to efficiently use the resources mining and staking pools attract. We start with developing predictions about factors that increase the efficient allocation of pools' resources. We then test our predictions based on a general model for optimal resource allocation that we develop, as well as data we collected on pools' actual resource allocations. We find that pools can increase resource efficiency by mining for more blockchains as well as by increasing the frequency of resource re-allocation. Further, we enroll to mining pools as a miner to understand and comment on how pools can encourage their miners to increase the efficiency of their allocation. While our empirical investigation mostly focuses on the BTC family, we show that our theory and results are general and applicable to the Ethereum family as well as other proof-of-work (PoW) and proof-of-stake (PoS) chains.
Mohsen Alambardar Meybodi, Amir Kafshdar Goharshady, M. R. Hooshmandasl, Ali Shakiba
Following the Bitcoin model, many modern blockchains reward their miners in two ways: (i) a base reward for each block that is mined, and (ii) the transaction fees of those transactions that are included in the mined block. The base reward is fixed by the respective blockchain's protocol and is not under the miner's control. Hence, for a miner who wishes to maximize earnings, the fundamental problem is to form a valid block with maximal total transaction fees and then try to mine it. Moreover, in many protocols, including Bitcoin itself, the base reward halves at predetermined intervals, hence increasing the importance of maximizing transaction fees and mining an optimal block. This problem is further complicated by the fact that transactions can be prerequisites of each other or have conflicts (in case of double-spending). In this work, we consider the problem of forming an optimal block, i.e. a valid block with maximal total transaction fees, given a set of unmined transactions. The problem is known to be NP-hard. As such, there is no hope in solving it efficiently for general instances. However, we observe that its real-world instances are quite sparse, i.e. the transactions have very few dependencies and conflicts. Using this fact, and exploiting a well-known graph sparsity parameter, namely pathwidth, we present an exact linear-time parameterized algorithm that is applicable to the real-world instances and obtains optimal results. We also provide an experimental evaluation demonstrating that our approach outperforms current Bitcoin miners in practice, obtaining a significant increase in transaction fee revenues.
This perspective highlights some recent progress on the research of Byzantine fault tolerant (BFT) consensus protocol in the era of blockchains, including both partially synchronous BFT and asynchronous BFT protocols, their fundamental building blocks, and their variants.
Mainstream cryptocurrencies, based on proof of work or stake, require paying miners for the capital-intensive execution of a consensus protocol, and hence are unsuitable as a foundation for capital-free digital communities and for the bootstrap of a grassroots digital society. We aim to adapt and adjust the concepts, tools and technologies developed by the cryptocurrencies ecosystem, together with related networking technologies, into a foundation for a healthy grassroots digital economy and society. In this context we present the design and proof-of-concept implementation of a self-sovereign digital agent (ssDA), as an essential building block for a grassroots digital economy and society. The ssDA serves as a party, on behalf of its sovereign—a person—in digital social contracts, which are smart contracts among vetted participants, who are its sovereign in that they jointly execute the contract with an egalitarian consensus protocol. Digital social contracts may realize social networks, sharing economy applications, social governance of a digital community, and more. The ssDA is a software application that allows a person to partake in multiple digital social contracts simultaneously. Participation in a contract can be realized by initiating it or by being invited to it. Extra confidence in the integrity of the data is achieved by each person maintaining a blockchain containing all the person’s transactions in all contracts.
Warlley Paulo Freire, Wilson S. Melo, Vinicius D. do Nascimento, Paulo R. Nascimento · 5 authors
Maritime Domain Awareness (MDA) is a strategic field of study that seeks to provide a coastal country with an effective monitoring of its maritime resources and its Exclusive Economic Zone (EEZ). In this scope, a Maritime Monitoring System (MMS) aims to leverage active surveillance of military and non-military activities at sea using sensing devices such as radars, optronics, automatic Identification Systems (AISs), and IoT, among others. However, deploying a nation-scale MMS imposes great challenges regarding the scalability and cybersecurity of this heterogeneous system. Aiming to address these challenges, this work explores the use of blockchain to leverage MMS cybersecurity and to ensure the integrity, authenticity, and availability of relevant navigation data. We propose a prototype built on a permissioned blockchain solution using HyperLedger Fabric-a robust, modular, and efficient open-source blockchain platform. We evaluate this solution's performance through a practical experiment where the prototype receives sensing data from a Software-Defined-Radio (SDR)-based low-cost AIS receiver built with a Raspberry Pi. In order to reduce scalability attrition, we developed a dockerized blockchain client easily deployed on a large scale. Furthermore, we determined, through extensive experimentation, the client optimal hardware configuration, also aiming to reduce implementation and maintenance costs. The performance results provide a quantitative analysis of the blockchain technology overhead and its impact in terms of Quality of Service (QoS), demonstrating the feasibility and effectiveness of our solution in the scope of an MMS using AIS data.
Margarita Capretto, MartÃn Ceresa, Antonio Fernández Anta, Antonio Russo · 5 authors
Blockchain technologies are facing a scalability challenge, which must be overcome to guarantee a wider adoption of the technology. This scalability issue is mostly caused by the use of consensus algorithms to guarantee the total order of the chain of blocks (and of the operations within each block). However, total order is often overkilling, since important advanced applications of smart-contracts do not require a total order of all the operations. Hence, if a more relaxed partial order (instead of a total order) is allowed under certain safety conditions, a much higher scalability can be achieved. In this paper, we propose a distributed concurrent data type, called Setchain, that allows implementing this partial order and increases significantly blockchain scalability. A Setchain implements a grow-only set object whose elements are not totally ordered, unlike conventional blockchain operations. When convenient, the Setchain allows forcing a synchronization barrier that assigns permanently an epoch number to a subset of the latest elements added. With the Setchain, operations in the same epoch are not ordered, while operations in different epochs are. We present different Byzantine-tolerant implementations of Setchain, prove their correctness and report on an empirical evaluation of a direct implementation. Our results show that Setchain is orders of magnitude faster than consensus-based ledgers to implement grow-only sets with epoch synchronization. Since the Setchain barriers can be synchronized with block consolidation, Setchain objects can be used as a sidechain to implement many smart contract solutions with much faster operations than on basic blockchains.
This dissertation is composed of two main research projects. The first, which was conducted with my adviser Xiaoming Song as a continuation of her work with with her previous student Nathan Anderson-Stahl. In that chapter, we consider a class of general backward stochastic differential equations and backward doubly stochastic differential equations to provide a standard method to prove the existence and uniqueness of the Lp solutions and to obtain the Lp estimates for the solutions. The other project was conducted in collaboration with Josh McGinnis and corresponds to the second chapter in which we provide a physical zero knowledge proof for the popular app game Flow Free. We then show that the methodology can be extended to provide zero knowledge proofs for the related graph problems of the paired many-to-many disjoint covering path problem, the unpaired many-to-many disjoint covering path problem and Hamiltonian cycles.
Piotr Macek, Daria Dziubałtowska, Bartosz Kuśmierz, Radosław Michalski
Every distributed system in which there is no central coordinator requires some form of agreement on its state and other aspects. Depending on the setting, there is also some possibility of additional risks, such as malicious or failing nodes, and this also contributes to the challenge of reaching consensus. In this work we investigate the problem of metastability in peer-to-peer networks that are used for distributed ledgers, especially focusing on cellular automata protocol with majority dynamics. Our results demonstrate that networks using this protocol do not reach consensus easily, even in the absence of an adversary. As a remedy for that, we propose a set of fixtures significantly increasing the probability of reaching network agreement that in best cases allow for achieving it two orders of magnitude more often compared to the basic cellular automata approach.
Eduardo Castelló Ferrer, Ivan Berman, Aleksandr Kapitonov, Vadim Manaenko · 6 authors
The physical autonomy of robots is well understood both theoretically and practically. By contrast, there is almost no research exploring their potential economic autonomy. In this paper, we present the first economically autonomous robot -- a robot able to produce marketable goods while having full control over the use of its generated income. Gaka-chu ("painter" in Japanese) is a 6-axis robot arm that creates paintings of Japanese characters from an autoselected keyword. By using a blockchain-based smart contract, Gaka-chu can autonomously list a painting it made for sale in an online auction. In this transaction, the robot interacts with the human bidders as a peer not as a tool. Using the blockchain-based smart contract, Gaka-chu can then use its income from selling paintings to replenish its resources by autonomously ordering materials from an online art shop. We built the Gaka-chu prototype with an Ethereum-based smart contract and ran a 6-month long experiment, during which the robot created and sold four paintings, simultaneously using its income to purchase supplies and repay initial investors. In this work, we present the results of the experiments conducted and discuss the implications of economically autonomous robots.
In distributed computations and cryptography, it is desirable to record events on a public ledger, such that later alterations are computationally infeasible. An implementation of this idea is called blockchain, which is a distributed protocol that allows the creation of an immutable ledger. While such an idea is very appealing, the ledger may be contaminated with incorrect, illegal, or even dangerous data, and everyone running the blockchain protocol has no option but to store and propagate the unwanted data. The ledger is bloated over time, and it is not possible to remove redundant information. Finally, missing data cannot be inserted later. Redactable blockchains were invented to allow the ledger to be mutated in a controlled manner. To date, redactable blockchains support at most two types of redactions: block modification and removal. The next logical step is to support block insertions. However, we show that this seemingly innocuous enhancement renders all previous constructs insecure. We put forward a model for blockchains supporting all three redaction operations and construct a blockchain that is provably secure under this formal definition.
Blockchain is the core of computer technology. It is cryptographically endangered distributed and parallelized database (DB) knowledge for storing and transmitting facts. Each tuple in the DB broadly called a block and covers such as the query timestamp and a link to the previous block. Blockchain and Big data are two expertises in full swing then again they are also two complementary expertise. We can study the how the Blockchain executes big query analysis. Many pursuits query only require the traditional approach of ranking a set of matching results. However, some queries require a more complex approach, either because they are broad or ambiguous. It is important for a DB search engine to identify such queries along with to differentiate broad queries from ambiguous ones. In this chapter, we propose that there is a diversity of indications that the Hadoop-based DB search engine is used. This allows the Hadoop DB search engine to explore and improve the query as correct relevant. The experiment result is measured by the query response time (RT) for optimized queries and broad queries.
Blockchain has become one of the most demanding technologies of the decade. Blockchain is a decentralised digital record of information stored in a form of blocks in a chain of blocks called blockchain. It is totally dependent on the addition of new block in its chain. At a single time, there are a number of blocks ready to be added in the blockchain; choosing one valid block from this number of blocks is a complex and most important part of blockchain architecture. As we know that blockchain is a non-centralised system, it has peer-to-peer network in which blocks are added one by one to the chain of blocks only when a consensus is reached amongst the participants of the network. This paper presents a theory summarising of some consensus algorithm used in public, private and consortium blockchain technology along with pros and cons of each algorithms.
Blockchain consensus is a state whereby each node in a network agrees on the current state of the blockchain. Existing protocols achieve consensus via a contest or voting procedure to select one node as a dictator to propose new blocks. However, this procedure can still lead to potential attacks that make consensus harder to achieve or lead to coordination issues if multiple, competing chains (i.e., forks) are created with the potential that an untruthful fork might be selected. We explore the potential for mechanisms to be used to achieve consensus that are triggered when there is a dispute impeding consensus. Using the feature that nodes stake tokens in proof of stake (POS) protocols, we construct revelation mechanisms in which the unique (subgame perfect) equilibrium involves validating nodes propose truthful blocks using only the information that exists amongst all nodes. We construct operationally and computationally simple mechanisms under both Byzantine Fault Tolerance and a Longest Chain Rule, and discuss their robustness to attacks. Our perspective is that the use of simple mechanisms is an unexplored area of blockchain consensus and has the potential to mitigate known trade-offs and enhance scalability.