P2P networks are the mechanism used by cryptocurrencies to disseminate system information while keeping the whole system as much decentralized as possible. Cryptocurrency P2P networks have new characteristics that propose new challenges and avoid some problems of existing P2P networks. By characterizing the most relevant cryptocurrency network, Bitcoin, we provide details on different properties of cryptocurrency networks and their similarities and differences with standard P2P network paradigms. Our study allows us to conclude that cryptocurrency networks present a new paradigm of P2P networks due to the mechanisms they use to achieve high resilience and security. With this new paradigm, interesting research lines can be further developed, both in the focused field of P2P cryptocurrency networks and also when such networks are combined with other distributed scenarios.
Blockchain-based cryptocurrencies have demonstrated how to securely implement traditionally centralized systems, such as currencies, in a decentralized fashion. However, there have been few measurement studies on the level of decentralization they achieve in practice. We present a measurement study on various decentralization metrics of two of the leading cryptocurrencies with the largest market capitalization and user base, Bitcoin and Ethereum. We investigate the extent of decentralization by measuring the network resources of nodes and the interconnection among them, the protocol requirements affecting the operation of nodes, and the robustness of the two systems against attacks. In particular, we adapted existing internet measurement techniques and used the Falcon Relay Network as a novel measurement tool to obtain our data. We discovered that neither Bitcoin nor Ethereum has strictly better properties than the other. We also provide concrete suggestions for improving both systems.
Oğuzhan Ersoy, Zhijie Ren, Zekeriya Erkin, Reginald L. Lagendijk
Existing permissionless blockchain solutions rely on peer-to-peer propagation mechanisms, where nodes in a network transfer transaction they received to their neighbors. Unfortunately, there is no explicit incentive for such transaction propagation. Therefore, existing propagation mechanisms will not be sustainable in a fully decentralized blockchain with rational nodes. In this work, we formally define the problem of incentivizing nodes for transaction propagation. We propose an incentive mechanism where each node involved in the propagation of a transaction receives a share of the transaction fee. We also show that our proposal is Sybil-proof. Furthermore, we combine the incentive mechanism with smart routing to reduce the communication and storage costs at the same time. The proposed routing mechanism reduces the redundant transaction propagation from the size of the network to a factor of average shortest path length. The routing mechanism is built upon a specific type of consensus protocol where the round leader who creates the transaction block is known in advance. Note that our routing mechanism is a generic one and can be adopted independently from the incentive mechanism.
Adoption of Cryptocurrency has grown significantly over the time and becoming more popular among young generation. People are calling it currency of new digital era. In this research work we are reviewing the dominant Cryptocurrency systems and its underlying disruptive Innovations and Technologies.
Ethereum, a cryptocurrency currently valued at 46 billion US dollars, has grown over 6,500% in the last 12 months. Despite the growth in value, we still have very limited Ethereum network visibility. In this thesis, we analyze the Ethereum network from two vantage points: the DEVp2p network and the Ethereum Mainnet. The DEVp2p peer-to- peer (P2P) network was developed specifically for and ultimately underlies the Ethereum Mainnet. We examine overall composition of the DEVp2p network. We analyze our peer connections on the Ethereum Mainnet—the main Ethereum network established on top of DEVp2p. We compare the Ethereum network’s properties to those of other well-studied P2P networks, namely BitTorrent and Gnutella. We develop novel techniques to measure the Ethereum P2P network and gain visibility into this previously opaque network.
Since the introduction of Bitcoin in 2008, blockchain systems have evolved immensely in terms of performance and usability. There is a massive focus on building enterprise blockchain solutions, with providers such as IBM and Microsoft already providing Blockchain-as-a Service (BaaS). To facilitate the adoption of blockchain technologies across various business verticals, we argue that middleware plays an integral role in accelerating the development of automated business processes (i.e., smart contracts). We argue that decentralized messaging is a key requirement of many distributed applications and should be provided as a reusable blockchain middleware. Our system, called HyperPubSub, provides decentralized publish/subscribe messaging for a multi-federated, permissioned, environment. HyperPubSub provides secure and privacy-preserving messaging, which is audited using blockchains for validation and monetization purposes. We demonstrate our implementation using Kafka and Hyperledger.
Yi Liu, Xiayang Chen, Lei Zhang, Chaojing Tang · 5 authors
Bitcoin is a digital cryptocurrency operating on a peer to peer network, which is currently integrated across a number of businesses and exchange markets. New bitcoins is created by participants who contribute computational resources to maintain a public blockchain as miners. Miners collaborate in a mining pool to reduce their variance and earn steadier rewards in Bitcoin. Each mining pool desires to make a profit in the competition against others. To this end, an intelligent mining strategy to enable a mining pool to attain higher probability to get rewards disproportional to its computational power is proposed in this paper. We deploy some forwarding nodes according to the distribution of Bitcoin nodes. This strategy can reduce time delay for messages propagation and increase the probability for new block to be appended on the longest blockchain. It is also easy to deploy in existing network with low expenditure.
Blockchain Technology Applications and Security
Advanced Steganography and Watermarking Techniques
Following the success of Bitcoin, Ethereum and Hyperledger, blockchains are now gaining widespread adoption in a wide variety of applications, using a diversity of distributed ledger systems with varying characteristics. Yet, beyond the original bitcoin protocol, the safety and reliability properties of such systems are not sufficiently analyzed. To better understand the behavior of these systems, we propose VIBES: a configurable blockchain simulator for large scale peer-to-peer networks. With VIBES, users can explore important characteristics and metrics of the network, reason about interactions between nodes, and compare different scenarios in an intuitive way. VIBES differentiates itself from previous works in its ability to simulate blockchain systems beyond bitcoin and its support for large-scale simulations with thousands of nodes.
IPFS [1] is a peer-to-peer version controlled filesystem that synthesizes learnings from many previous successful systems. IPFS combines a distributed Hash table, an incentivized block exchange, and a self-certifying namespace [1]. IPFS is a peer-to-peer hypermedia protocol to make the web faster, safer, and more open. According to the characteristics of IPFS, we propose an improved P2P file system scheme based on IPFS and Blockchain. We address the high-throughput problem for individual users in IPFS by introducing the role of content service providers. Consider data reliability and availability, storage overhead and other issues for service providers, we provide a novel zigzag-based storage model to improve the block storage model that IPFS provides. Moreover, we introduce blockchain to combine IPFS with this storage model. According to analysis, this proposed scheme can effectively solve the above problems.
This paper introduces some of the interdependent components within the multifaceted solution our team is developing towards accelerating the functionality, complexity and versatility of blockchain-enabled services. The focus here is particularly on introducing and bringing together selected individual components of the solution to achieve a synergistic effect in expanding the functionality of blockchain-enforced smart contracts. The contributions of this paper include: (i) proposing a method for automated management of contracts with hierarchical conditionality structures through an hierarchy of intelligent agents and the use of hierarchical cryptographic key-pairs; (ii) proposing a method for efficient and secure matching and transfer of smart-contract underlyings (entities) among disparate smart contracts/subcontracts; (iii) proposing a method for producing an hierarchy of common secrets to facilitate hierarchical communication channels of increased security, and applying this method both in the context of method (i) and method (ii); and (iv) proposing the use of distributed hash tables DHT in building secure and optimized repositories in the context of method (i) and in the context method (ii), where the former involves a DHT repository of smart contracts and the latter involves a DHT repository of entities underlying smart contracts that are being exchanged among different smart contracts and subcontracts. The smart-contract focused methods introduced in this paper contribute to the overall goal towards a sustainable adaptive mechanism for processing evolving volumes, versatility, and complexity of blockchain transactions, traffic, and services. Blockchain-enabled services are efficient, secure, automated, and allowing worldwide distribution of resources. They present a more efficient and sustainable alternative to current service infrastructures within a range of domains, particularly the legal and financial domains. They also set a sustainable infrastructure for emerging Internet-of-things services.
As blockchain technologies and cryptocurrencies increase in popularity, their decentralization poses unique challenges in network partitions. In traditional distributed systems, network partitions are generally a result of bugs or connectivity failures; the typical goal of the system designer is to automatically recover from such issues as seamlessly as possible. Blockchain-based systems, however, rely on purposeful "forks" to roll out protocol changes in a decentralized manner. Not all users may agree with proposed changes, and thus forks can persist, leading to permanent network partitions. In this paper, we closely study the large-scale fork that occurred in Ethereum, a new blockchain technology that allows for both currency transactions and smart contracts. Ethereum is currently the second-most-valuable cryptocurrency, with a market capitalization of over $28B. We explore the consequences of this fork, showing the impact on the two networks and their mining pools, and how the fork lead to unintentional incentives and security vulnerabilities.
Bitcoin is a peer to peer electronic payment system where payment transactions are stored in a data structure named the blockchain which is maintained by a community of participants. The Bitcoin Core protocol limits blocks to 1 MB in size. Each block contains at most some 4,000 transactions. Blocks are added to the blockchain on average every 10 minutes, therefore the transaction rate is limited to some 7 transactions per second (TPS). This is much less than the transaction rate offered by competing financial transaction processing systems. The Bitcoin TPS can be increased by increasing the block size and/or by decreasing the block discovery interval. Both of these interventions will increase the end-to-end block transmission delay, which in turn will increase the probability that different participants momentarily record different versions of the blockchain, so that the consensus protocol will discard an increasing number of blocks. The net effect is that the real increase in the TPS is not proportional to the increase (decrease) in the block size (block discovery rate). Our simulation experiments show that large block sizes, if accompanied by large end-to-end block transmission delays, give rise to the frequent appearance of inconsistent blockchain copies, to the detriment of the TPS. We present a simulation analysis of Bitcoin-Next Generation where blocks (keyblocks) stripped of transactions propagate rapidly through the peer-to-peer network. Once a keyblock is mined, only the miner of the keyblock is entitled to broadcast small microblocks of transactions until the next keyblock is mined and another miner is selected to broadcast microblocks. Initial simulation experiments show that Bitcoin-NG can sustain substantially larger transaction rates than Bitcoin Core.
The mining work concentration problem, whereby machine power is monopolized when supporting its operation, is becoming a serious problem in virtual currency using the blockchain technology that has drawn significant attention in recent years. The paper presents a new solution to solve the problem by using a simple virtual currency service that allows a user to operate the service by giving the user a new incentive based on gamification, not traditional economic incentives. We conducted experiments that show the feasibility of adopting the alternative incentive.
Ethereum contracts can be designed to function as fully decentralized applications called DAPPs that hold financial assets, and many have already been fielded. Unfortunately, DAPPs can be hacked, and the assets they control can be stolen. A recent attack on an Ethereum decentralized application called The DAO demonstrated that smart contract bugs are more than an academic concern. Ether worth hundreds of millions of US dollars was extracted by an attacker from The DAO, sending the value of its tokens and the overall exchange price of ether itself tumbling.
Andrea Pinna, Roberto Tonelli, Matteo Orrù, Michele Marchesi
A Blockchain is a global shared infrastructure where cryptocurrency transactions among addresses are recorded, validated and made publicly available in a peer-to-peer network. To date, the best known and important cryptocurrency is the bitcoin. In this paper, we focus on this cryptocurrency and in particular on the modeling of the Bitcoin Blockchain by using the Petri Nets formalism. The proposed model allows us to quickly collect information about identities owning Bitcoin addresses and to recover measures and statistics on the Bitcoin network. By exploiting algebraic formalism, we reconstructed an Entities network associated to Blockchain transactions gathering together Bitcoin addresses into the single entity holding permits to manage Bitcoins held by those addresses. The model allows also to identify a set of behaviors typical of Bitcoin owners, like that of using an address only once, and to reconstruct chains for this behavior together with the rate of firing. Our model is highly flexible and can easily be adapted to include different features of the Bitcoin cryptocurrency system. By exploiting algebraic formalism, we reconstructed an Entities network associated to Blockchain transactions gathering together Bitcoin addresses into the single entity holding permits to manage Bitcoins held by those addresses. The model allows also to identify a set of behaviors typical of Bitcoin owners, like that of using an address only once, and to reconstruct chains for this behavior together with the rate of firing. Our model is highly flexible and can easily be adapted to include different features of the Bitcoin cryptocurrency system.
Stefanie Roos, Pedro Moreno-Sánchez, Aniket Kate, Ian Goldberg
Path-based transaction (PBT) networks, which settle payments from one user to\nanother via a path of intermediaries, are a growing area of research. They\novercome the scalability and privacy issues in cryptocurrencies like Bitcoin\nand Ethereum by replacing expensive and slow on-chain blockchain operations\nwith inexpensive and fast off-chain transfers. In the form of credit networks\nsuch as Ripple and Stellar, they also enable low-price real-time gross\nsettlements across different currencies. For example, SilentWhsipers is a\nrecently proposed fully distributed credit network relying on path-based\ntransactions for secure and in particular private payments without a public\nledger. At the core of a decentralized PBT network is a routing algorithm that\ndiscovers transaction paths between payer and payee. During the last year, a\nnumber of routing algorithms have been proposed. However, the existing ad hoc\nefforts lack either efficiency or privacy. In this work, we first identify\nseveral efficiency concerns in SilentWhsipers. Armed with this knowledge, we\ndesign and evaluate SpeedyMurmurs, a novel routing algorithm for decentralized\nPBT networks using efficient and flexible embedding-based path discovery and\non-demand efficient stabilization to handle the dynamics of a PBT network. Our\nsimulation study, based on real-world data from the currently deployed Ripple\ncredit network, indicates that SpeedyMurmurs reduces the overhead of\nstabilization by up to two orders of magnitude and the overhead of routing a\ntransaction by more than a factor of two. Furthermore, using SpeedyMurmurs\nmaintains at least the same success ratio as decentralized landmark routing,\nwhile providing lower delays. Finally, SpeedyMurmurs achieves key privacy goals\nfor routing in PBT networks.\n
Harry Kalodner, Steven Goldfeder, Alishah Chator, Malte Möser · 5 authors
Analysis of blockchain data is useful for both scientific research and commercial applications. We present BlockSci, an open-source software platform for blockchain analysis. BlockSci is versatile in its support for different blockchains and analysis tasks. It incorporates an in-memory, analytical (rather than transactional) database, making it several hundred times faster than existing tools. We describe BlockSci's design and present four analyses that illustrate its capabilities. This is a working paper that accompanies the first public release of BlockSci, available at https://github.com/citp/BlockSci. We seek input from the community to further develop the software and explore other potential applications.
Blockchain is the latest buzzword in the FinTech scene and all companies big and small are vying to launch blockchain enabled products. At the basic technology level Blockchain is a distributed technology application. The challenges of operating such an application are known [1]. But the techniques of developing distributed applications by large enterprise teams, in a typical SDLC lifecycle (Develop, Test, Deploy and Upgrade) is not well known. Without proper methodologies / Formal Tools as is the case with most blockchain systems, bugs slip in easily. Studies on failures point to developers missing low handing bugs as most of the errors are simulated with 3 nodes or less [2]. The developer ecosystem is fast changing with technologies like containers and the emerging Micro Services architectures and Cloud Native Computing. The decisions on setup, build, CI/CD, Automated Testing are not taken at the beginning and as pointed out by [3] affect the entire project. The good news is that there are lot of tools available in the Open source domain that addresses the needs. The bad news is that picking the right combination to work in team sizes of 5 or more is not straight forward. This paper details our journey and lessons learnt on setting up Application Development Teams for Rapid Development in Blockchain using multiple blockchain tools like Ethereum and the HyperLedger Fabric. It details both our application architecture and the modifications needed to enable a Cloud Native architecture and the build/ deploy/ testing frameworks that we used.
Purwono Purwono, Alfian Ma’arif, Wahyu Rahmaniar, Qazi Mazhar ul Haq · 6 authors
Blockchain technology has a promising future in a number of industries and enterprises. Formerly connected to virtual currency like Bitcoin, blockchain has evolved into a versatile technology with many applications. In the upcoming years, it is predicted that blockchain will revolutionize a variety of industries, including banking, supply chain management, healthcare, voting systems, and more. The future of blockchain technology depends critically on its ability to increase security and transparency. By providing a decentralized and unchangeable record, eliminating the need for middlemen, and boosting participant confidence, blockchain promotes secure and traceable transactions. This transparency has the potential to transform whole industries by reducing fraud, streamlining processes, and increasing output. Blockchain also has the power to change financial systems. Blockchain-based smart contracts facilitate faster, more efficient transactions by automating and enforcing contractual agreements without the need for middlemen. By enabling speedier cross-border transactions, reducing costs, and boosting financial inclusion, tokenization and blockchain-based digital currencies have the potential to overturn conventional banking institutions. Blockchain’s key attributes, including decentralization, transparency, immutability, and security, make it a desirable choice for a range of organizations. Cross-border payments, trade finance, and smart contracts are just a few of the financial sector processes that blockchain technology has the potential to enhance and automate, lowering costs and increasing productivity. Additionally, the tamper-resistance of blockchain technology can boost transaction security and reliability, allowing for a wider use in traditional financial institutions. Outside of the financial industry, blockchain technology has a lot of promise, particularly in industries like supply chain management, healthcare, energy, intellectual property, and governance. By enabling transparent and traceable transactions, blockchain may improve supply chain efficiency, ensure product authenticity, and boost customer trust. By facilitating the secure exchange of patient data and research data, the decentralized nature of blockchain technology can enhance data security, interoperability, and privacy in the healthcare sector. A more decentralized and sustainable energy ecosystem may be supported by blockchain technology through peer-to-peer energy exchange, grid management, and monitoring of renewable energy certificates in the energy sector. Additionally, blockchain technology has the potential to transform decentralized governance structures, voting procedures, intellectual property rights, and digital identity management. By allowing people to own and manage their digital identities, blockchain can enhance privacy and reduce identity theft. Blockchain-based voting systems can offer transparency, security, and verifiability, thereby increasing voter turnout and public trust in democratic institutions. Blockchain can also enable the secure and transparent management of intellectual property rights, fostering author credit and just compensation.
Cüneyt Gürcan Akçora, Yulia R. Gel, Murat Kantarcıoğlu
Bitcoin and its underlying technology, blockchain, have gained significant popularity in recent years. Satoshi Nakamoto designed Bitcoin to enable a secure, distributed platform without the need for central authorities, and blockchain has been hailed as a paradigm that will be as impactful as Big Data, Cloud Computing, and Machine Learning. Blockchain incorporates innovative ideas from various fields, such as public-key encryption and distributed systems. As a result, readers often encounter resources that explain Blockchain technology from a single perspective, leaving them with more questions than answers. In this primer, we aim to provide a comprehensive view of blockchain. We will begin with a brief history and introduce the building blocks of the blockchain. As graph mining is a major area of blockchain analysis, we will delve into the graph-theoretical aspects of Blockchain technology. We will also discuss the future of blockchain and explain how extensions such as smart contracts and decentralized autonomous organizations will function. Our goal is to provide a concise but complete description of blockchain technology that is accessible to readers with no prior expertise in the field.
Peer-to-peer (P2P) design offers many benefits over a single-master or a multi-master architecture in terms of scalability, reliability and independence. The Clondike project is being converted from a grid computing system into a universal non-dedicated P2P cluster where every participating node can benefit from its membership in the cluster. But different design requires different types of algorithms in order to guarantee the same functionality. One of the challenges in P2P design is a fair scheduling and a general protection of the whole cluster against abusive or malfunctioning nodes. Algorithms used in a single-master or multi-master clusters do not work anymore. We have designed a multi-level system based on one of the main principles of cryptocurrencies to achieve a distributed master-less reputation rating across the cluster. This paper discusses proposed cluster multi-level reputation system and its parameters. The system is evaluated on a Clondike cluster on an experimental measurement with abusive nodes involved.