Blockmania is a byzantine consensus protocol. Nodes emit blocks forming a directed acyclic graph (block DAG) that is subsequently interpreted by each node separately to ensure consensus with safety, liveness and finality. The resulting system has communication complexity $O(N^2)$ even in the worse case, and very low constant factors --- as compared to $O(N^4)$ for PBFT; it is leaderless; and network operations do not depend on the composition of the quorum or node stake. This makes Blockmania very efficient (leading to over 400K transactions per second on a wide area network), and ideal for dynamic membership and flexible and non-interrupted proof-of-stake protocols. A X-Blockmania variant, has $O(N)$ communication cost but also higher latency $O(\log N)$.
Fedor Muratov, Andrei Lebedev, Nikolai Iushkevich, Bulat Nasrulin · 5 authors
Consensus in decentralized systems that asynchronously receive events and which are subject to Byzantine faults is a common problem with many real-life applications. Advances in decentralized systems, such as distributed ledger (i.e., blockchain) technology, has only increased the importance of finding performant and secure solutions to consensus of state machine replication in decentralized systems. YAC is a practical decentralized consensus algorithm, that solves the problems of inefficient message passing and strong leaders that occur in classical Byzantine fault tolerant consensus algorithms. The algorithm is open source and currently is used to provide Byzantine fault tolerant consensus for the Hyperledger Iroha blockchain project. We provide proofs of safety and liveness, as well as empirical results showing that our algorithm can scale to dozens of validating peers.
The main utility of blockchain networks stem from their ability to offer a trusted platform for execution of processes. The default blockchain implementation, where an immutable log of all transactions is maintained by every participant, is (i) inefficient, and (ii) does not scale well. This paper outlines several strategies to improve the scope and scale of processes that can be executed in a blockchain.
Blockchain technology is digitally revolutionizing the transfer and storage of assets. It is forming the backbone of all modern exchange and database reliant applications. The reliance on blockchain is pivoted on its property of being immutable. This prevents possibilities of corruption, fraud, and theft observed in current systems. Our study reviews the Blockchain technology and articulates the need and concept, which establishes it as a suitable alternative to conventional methods, its distinct types, the actors involved, the working of blockchain and the execution of a transaction on the blockchain. The main methods of finding consensus are explained. A brief comparison to centralized systems has been done and its strengths and weaknesses have been outlined. Furthermore, its applications in various domains are discussed in detail. An overview of currently live applications in these domains like bitcoin for cryptocurrency is made, and the role of blockchain in these applications is discussed. We also lay out its future scope and vulnerabilities including lack of regulation and potential security flaws. This study is relevant to both the novice and informed reader, as the need, basic fundamentals and the concept behind the technology and the advanced applications and protocols are discussed in detail.
Wei‐Tek Tsai, Zihao Zhao, Chi Zhang, Lian Yu · 5 authors
Recently digital currency has received significant attention, and among many topics within digital currency, CBDC (Central Bank issued Digital Currency) has been a hot topic as it will affect national currency systems. RSCoin is the first CBDC model sponsored by Bank of England, and it uses the UTXO model from Bitcoin. This paper proposes a new CBDC model Panda model that can store account balance like current banking systems, but use efficient consensus protocols to ensure that relevant parties have consistent views of transactions and accounts. The Panda model is scalable as it can include as many financial institutions or individuals as possible in the system with increasing or decreasing workloads. The model has been simulated in the TaiShan Sandbox in Qingdao.
Akash Sarda, Vijesh Ghandare, Aditya Malu, Jibi Abraham
In the last decade, there has been an exponential growth in the number of cryptocurrencies and the technology that underpins all the cryptocurrencies is the Blockchain. The blockchain serves as a decentralized, cryptographically signed ledger that enables payments in a trustless manner. While there are limitless applications of the blockchain, the problem that persists is the limited scaling of the blockchain. The bitcoin blockchain and the ethereum blockchain, are able to process only 7 transactions per second and 15 transactions per second respectively. All the participating mining nodes in the blockchain network perform heavy computation and compete to mine a block, but only one of them succeeds and others waste their computation. In this paper, we propose a new node count based transaction propagation protocol for less competitive mining called as NoCo. NoCo distributes a transaction from a node to the nearby miners based on the node count between them and thereby decreasing the competition, and hence this is beneficial for the miners as well as for the networks scalability. The protocol tries to parallelize the mining in the network. The protocol scales the transaction rates almost linearly.
This paper build the foundations of a simulation tool for blockchain-based applications. It takes advantage of the huge expressiveness and extensibility of PyCATSHOO framework to deal with the important variability of blockchain implémentations and properties of interest. A simple stochastic model of generic blockchain-style distributed consensus system and associated performance indicators are proposed (performance in terms of consistency and ability to discard double-spending attacks). Monte Carlo simulations are applied to assess the indicators and determine their sensitivity to the variation of input parameters.
Blockchains are known to provide verifiable tamper-resistant trails of accepted transactions. This guarantee comes at the considerable cost of storage and computational power, thereby restricting its application. Current research has focused on alternatives such as proof of reputation, proof of stake, and proof of elapsed-time to reduce the computational burden on the blockchain participants. Orthogonal to this effort, we focus on a specific set of applications that cannot commit much storage space and computational resources, but require only reasonable guarantees on the validity of transactions. To this end, we introduce blockchain design alternatives, collectively called ApproxBC, that can provide proof of transactions with provable confidence bounds. Consequently, ApproxBC can considerably reduce the computation and storage resources required, making them suitable for resource-constrained Internet of Things environments. We also showcase two approximation-tolerant applications that can leverage the quicker computation and smaller storage requirements.
In this article, we study ongoing blockchain and distributed ledger technologies (DLT) standardization. To this end, we list standards organizations and the efforts they devote to standardise blockchain and DLT. We then identify a lack of terminology that can hamper communication on this topic and propose clarifications to address these ambiguities. Finally, we propose a high-level description of blockchain and DLT by describing three elements of their functional architecture.
Alin Bogdan Popa, Ioan Mihail Stan, Răzvan Rughiniş
Blockchain is one of the most important technological trends today since it has a wide spectrum of use cases (financial industry applications, supply-chain tracking, MedTech EHR management, energy grid etc.) and it offers a wide range of implementations. However, the main goal of the Blockchain remains the transfer of value-bearing assets between an owner of a resource and a client. Due to CPU intensive consensus algorithms, transaction prioritization based on potential earnings, the validation process and so on, Blockchain implementations are not able to support real-time services and, also, to enable a varied cloud computing service catalog on top of the existing infrastructure. Our solution is addressing this drawback by developing a system supporting late payments through our innovative concept called latent-transactions. We also provide the instruments through which we make viable off-chain agreements, between the parties involved in a transaction. Therefore, one can benefit from a service, prior to actual payment. In addition, we offer a service enlargement mechanism by providing a catalog where any member of Blockchain can subscribe and from where one can sell services in a real-time manner with adaptive pricing, based on the context (demand, activity at runtime etc.).
In 2008, Satoshi Nakamoto famously invented bitcoin, and in his (or her, or their, or its) white paper sketched an approximate formula for the probability of a successful double spending attack by a dishonest party. This was corrected by Meni Rosenfeld, who, under more realistic assumptions, gave the exact probability (missing a foundational proof); and another formula (along with foundational proof), in terms of the Incomplete Beta function, was given later by Cyril Grunspan and Ricardo Pérez-Marco, that enabled them to derive an asymptotic formula for that quantity. Using Wilf-Zeilberger algorithmic proof theory, we continue in this vein and present a recurrence equation for the above-mentioned probability of success, that enables a very fast compilation of these probabilities. We next use this recurrence to derive (in algorithmic fashion) higher-order asymptotic formulas, extending the formula of Grunspan and Pérez-Marco who did the leading term. We then study the statistical properties (expectation, variance, etc.) of the duration of a successful attack.
This thesis focuses on aspects related to the functioning of the gossip\nnetworks underlying three relatively popular cryptocurrencies: Ethereum, Nano\nand IOTA.\n We look at topics such as automatic discovery of peers when a new node joins\nthe network, bandwidth usage of a node, message passing protocols and storage\nschemas and optimizations for the shared ledger. We believe this is a topic\nthat is often overlooked in works about blockchains and cryptocurrencies.\nVulnerabilities and inefficiencies attain a higher significance than ones in a\nregular open source project because of the rather direct financial implications\nof these projects. Barring Bitcoin, a network that has been around for nearly\n10 years, no other project has substantial documentation for its operational\ndetails other than scattered and sparse pages in the source code repositories.\nAlmost all of the content described here has been extracted by studying the\nsource code of the reference implementations of these projects.\n We evaluate the use of Invertible Bloom Lookup Tables and the Graphene\nprotocol to decrease block propagation times and bandwidth usage of certain\nmessages. We perform realistic simulations that show significant improvements.\nWe provide a complete implementation of Graphene in Geth, Ethereum's main node\nsoftware and test this implementation against the main Ethereum blockchain.\n We also crawled the chosen cryptocurrency networks for publicly visible nodes\nand provide an Autonomous System-level breakdown of these nodes with the end\ngoal of estimating the ease of performing attacks such as BGP hijacks and their\nimpact.\n Code written for implementing Graphene in Geth, performing various\nsimulations and for other miscellaneous tasks has been uploaded to Github at\nhttps://github.com/sunfinite/masters-thesis.\n
Existing permissioned blockchain systems designate a fixed and explicit group of committee nodes to run a consensus protocol that confirms the same sequence of blocks among all nodes. Unfortunately, when such a permissioned blockchain runs in a large scale on the Internet, these explicit committee nodes can be easily turned down by denial-of-service (DoS) or network partition attacks. Although work proposes scalable BFT protocols that run on a larger number of committee nodes, their efficiency drops dramatically when only a small number of nodes are attacked. In this paper, our EGES protocol leverages Intel SGX to develop a new abstraction called "stealth committee", which effectively hides the committee nodes into a large pool of fake committee nodes. EGES selects a distinct group of stealth committee for each block and confirms the same sequence of blocks among all nodes with overwhelming probability. Evaluation on typical geo-distributed settings shows that: (1)EGES is the first permissioned blockchain's consensus protocol that can tolerate tough DoS and network partition attacks; and (2) EGES achieves comparable throughput and latency as existing permissioned blockchains' protocols
Consensus is one of the key problems in blockchains. There are many articles analyzing the performance of threat models for blockchains. But the network stability seems lack of attention, which in fact affects the blockchain performance. This paper studies the performance of a well adopted consensus algorithm, Raft, in networks with non-negligible packet loss rate. In particular, we propose a simple but accurate analytical model to analyze the distributed network split probability. At a given time, we explicitly present the network split probability as a function of the network size, the packet loss rate, and the election timeout period. To validate our analysis, we implement a Raft simulator and the simulation results coincide with the analytical results. With the proposed model, one can predict the network split time and probability in theory and optimize the parameters in Raft consensus algorithm.
Aug 1, 2018·2018 2nd International Conference on I-SMAC (IoT in Social, Mobile, Analytics and Cloud) (I-SMAC)I-SMAC (IoT in Social, Mobile, Analytics and Cloud) (I-SMAC), 2018 2nd International Conference on
Achampet Harshavardhan, T. Vijayakumar, S. R. Mugunthan
Blockchain, the establishment of Bitcoin, has gotten broad considerations as of late. Blockchain fills in as an unchanging record which permits exchanges occur in a decentralized way. In spite of the fact that the component of blockchain advances may bring us more dependable and advantageous administrations, the security issues and difficulties behind this imaginative strategy is additionally an essential point that we have to concern. We give an outline of blockchain engineering initially and look at some common accord calculations utilized as a part of various blockchains. Moreover, this paper indicates how blockchain is utilized as a part of cloud storage and increase in security measures.
Sachin M. Kolekar, Rahul P. More, Smita S. Bachal, Anuradha Yenkikar
Blockchain technologies are secure massive power in the last few years. Block chains are distributed ledgers that facilitate parties who do not steady trust each other to maintain a set of ecumenical states. The parties concur on the easiness, standards and histories of the states. As the technology backdrop is enlarge swiftly, it is mutually consequential and arduous to have a rigid grasp of what the foundation technologies have to offer, particularly with difference to their data dealing out capabilities. In this paper, we first survey the state of the art, fixating on secretive block chains. We analyze both in-engenderment and research systems in four dimensions: disseminated ledger, intrusion detection, consortium Blockchain, consensus protocol and perspicacious agreement. We then present BLOCKBENCH, a criterion skeleton for understanding performance of private block chains and public Blockchain. In this chapter we have discussed the circumscriptions of Blockchain.
The existing data sharing models have some issues such as poor transparency of data transactions, data without security assurance and lacking of effective data tracking methods. This paper proposed a brand-new data sharing scheme based on blockchain technology. Firstly, a blockchain double-chain structure about blockchain was introduced, one chain was used to store the original data and another was used to store transaction data generated by transactions. This structure separated the original data storage and data transactions. Secondly, combined with proxy re-encryption technology, safe and reliable data sharing were achieved. Finally, a new design was implemented. The logical structure of data transaction records enables data to be traced. The results of correctness and security analysis showed that this scheme can provide new technical ideas and methods for big data sharing and data trace.
In the area of IoT (Internet of Things), more and more intelligent devices are being connected to the Internet. These intelligent devices have been producing a huge amout of useful data over time, however there is still a lack of a platform which can efficiently transfer and utilize the value of the massive IoT data. Blockchain is able to transfer value with a relative low cost, which makes it possible for the data from smart devices to create economic value. This work of this paper is to design a high performance blockchain platform, using technologies such as distributed network architecture, intelligent devices node mapping, as well as PBFT-DPOC consensus algorithm to realize the decentralized autonomy of intelligent devices.
Sujaya Maiyya, Victor Zakhary, Divyakant Agrawal, Amr El Abbadi
Bitcoin is a successful and interesting example of a global scale peer-to-peer cryptocurrency that integrates many techniques and protocols from cryptography, distributed systems, and databases. The main underlying data structure is blockchain, a scalable fully replicated structure that is shared among all participants and guarantees a consistent view of all user transactions by all participants in the cryptocurrency system. In this tutorial, we discuss the basic protocols used in blockchain, and elaborate on its main advantages and limitations. To overcome these limitations, we provide the necessary distributed systems background in managing large scale fully replicated ledgers, using Byzantine Agreement protocols to solve the consensus problem. Finally, we expound on some of the most recent proposals to design scalable and efficient blockchains. The focus of the tutorial is on the distributed systems and database technical aspects of the recent innovations in blockchains.
In blockchain systems, especially cryptographic currencies such as Bitcoin, the double-spending and Byzantine-general-like problem are solved by reaching consensus protocols among all nodes. The state-of-the-art protocols include Proof-of-Work, Proof-of-Stake and Delegated-Proof-of-Stake. Proof-of-Work urges nodes to prove their computing power measured in hash rate in a crypto-puzzle solving competition. The other two take into account the amount of stake of each nodes and even design a vote in Delegated-Proof-of-Stake. However, these frameworks have several drawbacks, such as consuming a large number of electricity, leading the whole blockchain to a centralized system and so on. In this paper, we propose the conceptual framework, fundamental theory and research methodology, based on artificial intelligence technology that exploits nearly complementary information of each nodes. And we designed a particular convolutional neural network and a dynamic threshold, which obtained the super nodes and the random nodes, to reach the consensus. Experimental results demonstrate that our framework combines the advantages of Proof-of-Work, Proof-of-Stake and Delegated-Proof-of-Stake by avoiding complicated hash operation and monopoly. Furthermore, it compares favorably to the three state-of-the-art consensus frameworks, in terms of security and the speed of transaction confirmation.
Aug 1, 2018·2018 17th IEEE International Conference On Trust, Security And Privacy In Computing And Communications/ 12th IEEE International Conference On Big Data Science And Engineering (TrustCom/BigDataSE)
Andreas Abraham, Kevin Theuermann, Emanuel Kirchengast
Traditional identity management systems (IdMS) suffer from significant weaknesses, such as the reliance on a single central entity that provides the identity data or the users lack control over their identity data. The introduction of qualified self-sovereign identities (SSIs) for eGovernment systems can strengthen the privacy of citizens. Furthermore, it is possible to solve fundamental trust issues of traditional IdMS by utilizing distributed ledger technology (DLT) together with performing a consensus algorithm. The contribution of this paper is twofold. First, this paper proposes a solution for the derivation of qualified electronic identities (eIDs), issued by a traditional IdMS, into a distributed ledger (DL) based IdMS that enables SSIs. Second, we have implemented a proof-of-concept (PoC) realizing qualified eID derivation into an SSI system based on the DLT. This PoC was realized, among others, by introducing an agent that represents the interface between the traditional IdM and the SSI system as well as by extending the consensus algorithm. The proposed approach used for eID derivation ensures the maintenance of the trust as well as the quality of the identity data.
The decentralized nature of existing and future wireless network topologies has opened some unique opportunities for DLT to play a role in communications. In this column, we have reviewed the basic operation of a consensus mechanism, as well as the current trend of a DLT-based security model that is particularly important for loT. We further point out that, beyond application layer and security, DLT also has potential in other aspects of wireless networking such as computing and radio connectivity. Specifically, we see DLT as a perfect tool that should be leveraged to realize fog -RAN, as the consensus mechanism of DLT may be used to maintain tight synchronization among computing and networking resources in different locations. On the other hand, DLT could also be employed to avoid potential collision that may occur in grant -free uplink access. In summary, we believe that DLT will gradually become a key tool to reshape communication systems in a wide range of aspects, covering not just applications and security, but also connectivity and computing.