Despite the enormous potential of distributed ledgers such as blockchain to increase revenue and lower costs, telecom firms have been slower than other regulated industries to integrate blockchain into its operations. We examine how three backend tasks currently performed by telecoms (managing roaming agreements, mobile number portability, and inter-carrier settlement) can be accomplished with greater efficiency using ordered transactions in Hyperledger Fabric - a permissioned blockchain framework. We also explore the role of peer types in the ordering process, how these integrate with Raft ordering service, as well as how several peculiarities in telecom can be addressed using chaincode - Fabric's version of smart contracts.
Distributed consensus mechanisms have been widely researched and made popular with a number of blockchain-based token applications, such as Bitcoin, and Ethereum. Although these general-purpose platforms have matured for scale and security, they are designed for human incentive and continue to require currency reward and contract functions that are not requisite in machine communications. Redes Chain is a custom designed blockchain, built to support fully decentralized self-organization in wireless networks-without a cryptocurrency or contract dependency.
An ideal distributed storage solution must have the ability to provide redundant, reliable, shared and secure access to user data without compromising the ability to scale and descend while maintaining performance. VAULT is an attempt to avert the negatives of the cloud in a local environment using a decentralized methodology. VAULT makes use of individual idle storage space on a network of peer-to-peer nodes which is then provided to an end user to store files in the pooled space. VAULT implements redundancy by the use of Reed-Solomon codes and maps file fragment locations using a blockchain as a distributed ledger. Fragment distribution is optimized using a machine learning approach where node characteristics are used to determine the reliability of each node. The aggregation of above features makes VAULT an ideal solution for corporate environments where consumer hardware and infrastructure is already allocated.
The success and popularity of Bitcoin mainly focuses the underlying blockchain technology which is totally immutable distributed ledger, highly secured by its P2P network consensus named Proof of Work (PoW). One of the worst threats to a Proof-of-Work based cryptocurrency is 51% attack. If one or more dishonest network peer gains more than 50% of resource such as processing power, then they will become the majority decision maker in the network. It is already proved that mixing of two or more existing protocol that is called hybrid protocol can make the network enough resistive to this attack. The recent implementations of hybrid protocols have other limitations and problems that they are facing and striving to resolve. But their main weakness is in distribution of block mining reward to the investors. From the perspective of an investor, an investor invests his hard-earned money in a cryptocurrency for making proper profit from his investment. The main source of this profit is the block reward which is generated and given to the miner on successful mining of a block. So, to ensure this profit is given to proper user on proper time interval, the consistency of block generation time interval is a vital factor. The voting system, ticket system etc. are not time controlled and over all block reward generation interval will not show a uniform distribution of profit. Another big issue is diversifying the peers by creating special committee and groups of validators the concept of P2P network is violated. In this paper we will describe a step by step process to implement a Hybrid PoW-PoS based consensus protocol. In our proposed system, the PoW mining process is only used to regulate the block generation time. The actual block generation is done by the same user with PoS consensus mechanism. There is no voting or validating committee. The entire network will validate each block. This is the major difference with other discussed system. The system will not only be able to tackle the 51% attack, it provides a uniform distribution of mining reward to the stake holders and investors by maintaining a precise block generation interval with difficulty adjustment in PoW mining and probability calculation for stake holders according to their matured staking balance. We will not only show how to make the system non-vulnerable to this attack but also describe in detail about how to validate the transactions and blocks in different stage of creating the block chain.
Online publishing of news and information enables important content to reach a much larger audience than traditional paper publishing, but there is no guarantee of long-term, reliable, and persistent access to the content. Over time, links "decay" because they are not reliably updated when content changes location, or even worse, content is deliberately altered from its original published form or deleted altogether. We present the design of Watchdog, a permissioned distributed ledger that securely and reliably monitors and preserves dynamic web content such as government and news sites. Unlike prior preservation systems, our system design allows nodes to be dispersed across multiple administrative domains, thus eliminating single points of trust and at the same time, is the first to monitor how content changes both over time and across geographical location. Watchdog achieves Byzantine fault-tolerance via a novel interactive consistency algorithm that offers a twist on the traditional definition and use of interactive consistency; the algorithm enables a set of mutually suspicious nodes, with arbitrary-sized, potentially overlapping data collections, to efficiently agree on the exact data collection in possession by each node. We demonstrate how our algorithm enables Watchdog nodes to exchange and agree upon the content each has observed individually, in a fault-tolerant, tamper-proof manner.
Proof of Stake (PoS) is a burgeoning Sybil resistance mechanism that aims to have a digital asset ("token") serve as security collateral in crypto networks. However, PoS has so far eluded a comprehensive threat model that encompasses both Byzantine attacks from distributed systems and financial attacks that arise from the dual usage of the token as a means of payment and a Sybil resistance mechanism. In particular, the existence of derivatives markets makes malicious coordination among validators easier to execute than in Proof of Work systems. We demonstrate that it is also possible for on-chain lending smart contracts to cannibalize network security in PoS systems. When the yield provided by these contracts is more attractive than the inflation rate provided from staking, stakers will tend to remove their staked tokens and lend them out, thus reducing network security. In this paper, we provide a simple stochastic model that describes how rational validators with varying risk preferences react to changes in staking and lending returns. For a particular configuration of this model, we provide a formal proof of a phase transition between equilibria in which tokens are predominantly staked and those in which they are predominantly lent. We further validate this emergent adversarial behavior (e.g. reduced staked token supply) with agent-based simulations that sample transitions under more realistic conditions. Our results illustrate that rational, non-adversarial actors can dramatically reduce PoS network security if block rewards are not calibrated appropriately above the expected yields of on-chain lending.
Previous work presented a theoretical model based on the implicit Bitcoin specification for how an entity might issue a protocol native cryptocurrency that mimics features of fiat currencies. Protocol native means that it is built into the blockchain platform itself and is not simply a token running on another platform. Novel to this work were mechanisms by which the issuing entity could manage the cryptocurrency but where their power was limited and transparency was enforced by the cryptocurrency being implemented using a publicly mined blockchain. In this work we demonstrate the feasibility of this theoretical model by implementing such a managed cryptocurrency architecture through forking the Bitcoin code base. We discovered that the theoretical model contains several vulnerabilities and security issues that needed to be mitigated. It also contains architectural features that presented significant implementation challenges; some aspects of the proposed changes to the Bitcoin specification were not practical or even workable. In this work we describe how we mitigated the security vulnerabilities and overcame the architectural hurdles to build a working prototype.
Open access
3 source records
cs.CR
Blockchain Technology Applications and Security
Advanced Steganography and Watermarking Techniques
Over the last decade there has been a continuing decline in social trust on the part of individuals with regards to the handling and fair use of personal data, digital assets and other related rights in general. At the same time, there has been a change in the employment patterns for many people through the emergence of the gig economy. These gig workers include artists, songwriters and musicians in the music industry. We discuss the notion of the data cooperative with fiduciary responsibilities to its members, which is similar in purpose to credit unions in the financial sector. A data cooperative for artists and musicians allows the community to share IT resources, such as data storage, analytics processing, blockchains and distributed ledgers. A cooperative can also employ smart contracts to remedy the various challenges currently faced by the music industry with regards to the license tracking management.
We introduce Unity Interleave, a new consensus algorithm for public blockchain settings. It is an eventual consistency protocol merging the Proof-of-Work (PoW) and Proof-of-Stake (PoS) into a coherent stochastic process. It builds upon research previously done for the Unity protocol, improving security while maintaining fairness and scalability.
Suyash Gupta, Jelle Hellings, Sajjad Rahnama, Mohammad Sadoghi
Since the introduction of Bitcoin---the first wide-spread application driven by blockchains---the interest of the public and private sector in blockchains has skyrocketed. At the core of this interest are the ways in which blockchains can be used to improve data management, e.g., by enabling federated data management via decentralization, resilience against failure and malicious actors via replication and consensus, and strong data provenance via a secured immutable ledger.
Atomic Crosschain Transaction technology allows composable programming across private Ethereum blockchains. It allows for inter-contract and inter-blockchain function calls that are both synchronous and atomic: if one part fails, the whole call graph of function calls is rolled back. Traditional Ethereum contract functions can limit which accounts can call them by specialised application program logic. This is important as it allows application developers to specify which callers can execute functions that update contract state. In this paper we introduce the strategy required to restrict which contracts on one blockchain can call a function in a contract that is deployed on another blockchain. We show that validating the Originating Blockchain Id (the blockchain the crosschain function call started on), From Blockchain Id, and From Account provides contracts with certainty that a function call came from a specific contract on a specific blockchain.
Blockchain systems (more precisely Distributed Ledger Technologies (DLTs)) represent a different digital ecosystem compared with traditional computer systems. One major difference are the performance and scalability factors which will be discussed and analytically investigated in this paper. In doing so, we provide guidance for defining a research agenda focusing on the investigation of the crucial role of scalability for blockchain systems. System performance -- measured in terms of (1) consensus response time (blockchain network latency or time to convergence/agreement); (2) number of transactions per second or throughput, and (3) computing (and power) resources consumed -- can be understood by considering the design dimensions of a blockchain system, namely: (i) the type of blockchain system needed from a requirements perspective which in turn determines; (ii) the complexity of the consensus protocol used; (iii) the topography of the traffic flow on the network; (iv) the performance and complexity of the domain-specific language that implements smart contracts; and (v) by the anticipated growth in size and complexity of the distributed ledger itself.
The problem of peer selection, which randomly selects a peer from a set, is commonplace in Proof-of-Stake (PoS) protocols. In PoS, peers are chosen randomly with probability proportional to the amount of stake that they possess. This paper presents an approach that relates PoS peer selection to Roulette-wheel selection, which is frequently used in genetic and evolutionary algorithms or complex network modelling. In particular, we introduce the use of stochastic acceptance algorithm [6] for fast peer selection. The roulette-wheel selection algorithm [6] achieves O(1) complexity based on stochastic acceptance, whereas searching based algorithms may take O(N ) or O(logN ) complexity in a network of N peers.
The aim of this work is to analyze the major existing cryptocurrency consensus algorithms considering a number ofattributes that may play a significant role in the long-term sustainability of a cryptocurrency ecosystem and to comparativelyevaluate
Christoph Egger, Pedro Moreno-Sánchez, Matteo Maffei
Current cryptocurrencies provide a heavily limited transaction throughput that is clearly insufficient to cater their growing adoption. Payment-channel networks (PCNs) have emerged as an interesting solution to the scalability issue and are currently deployed by popular cryptocurrencies such as Bitcoin and Ethereum. While PCNs do increase the transaction throughput by processing payments off-chain and using the blockchain only as a dispute arbitrator, they unfortunately require high collateral (i.e., they lock coins for a non-constant time along the payment path) and are restricted to payments in a path from sender to receiver. These issues have severe consequences in practice. The high collateral enables denial-of-service attacks that hamper the throughput and utility of the PCN. Moreover, the limited functionality hinders the applicability of current PCNs in many important application scenarios. Unfortunately, current proposals do not solve either of these issues, or they require Turing-complete language support, which severely limit their applicability.
Blockchain interoperability, which allows state transitions across different blockchain networks, is critical functionality to facilitate major blockchain adoption. Existing interoperability protocols mostly focus on atomic token exchanges between blockchains. However, as blockchains have been upgraded from passive distributed ledgers into programmable state machines (thanks to smart contracts), the scope of blockchain interoperability goes beyond just token exchanges. In this paper, we present HyperService, the first platform that delivers interoperability and programmability across heterogeneous blockchains. HyperService is powered by two innovative designs: (i) a developer-facing programming framework that allows developers to build cross-chain applications in a unified programming model; and (ii) a secure blockchain-facing cryptography protocol that provably realizes those applications on blockchains. We implement a prototype of HyperService in approximately 35,000 lines of code to demonstrate its practicality. Our experiments show that (i) HyperService imposes reasonable latency, in order of seconds, on the end-to-end execution of cross-chain applications; (ii) the HyperService platform is scalable to continuously incorporate new large-scale production blockchains.
The concept of a blockchain was invented by Satoshi Nakamoto to maintain a distributed ledger. In addition to its security, important performance measures of a blockchain protocol are its transaction throughput and confirmation latency. In a decentralized setting, these measures are limited by two underlying physical network attributes: communication capacity and speed-of-light propagation delay. In this work we introduce Prism, a new proof-of-work blockchain protocol, which can achieve 1) security against up to 50% adversarial hashing power; 2) optimal throughput up to the capacity C of the network; 3) confirmation latency for honest transactions proportional to the propagation delay D, with confirmation error probability exponentially small in the bandwidth-delay product CD; 4) eventual total ordering of all transactions. Our approach to the design of this protocol is based on deconstructing Nakamoto's blockchain into its basic functionalities and systematically scaling up these functionalities to approach their physical limits.
The recent surge in blockchain applications and database systems has renewed the interest in traditional Byzantine Fault Tolerant consensus protocols (BFT). Several such BFT protocols follow a primary-backup design, in which a primary} replica coordinates the consensus protocol. In primary-backup designs, the normal-case operations are rather simple. At the same time, primary-backup designs place an unreasonable burden on primaries and allows malicious primaries to affect the system throughput substantially, however. To resolve this situation, we propose the MultiBFT paradigm, a protocol-agnostic approach towards improving the performance of primary-backup consensus protocols. At the core of MultiBFT is an approach to continuously order the client-transactions by running several instances of the underlying BFT protocol in parallel. We bring forth our paradigm to two well-established BFT protocols and demonstrate that the rendered parallelized protocols are not only safe and live but also significantly outperform, up to $2\times$, their original non-parallelized forms. Further, we show that our MultiBFT paradigm reaches a throughput of up to $320$K transactions per second.
Bitcoin-NG, a scalable blockchain protocol, divides each block into a key block and many micro blocks to effectively improve the transaction processing capacity. Bitcoin-NG has a special incentive mechanism (i.e. splitting transaction fees to the current and the next leader) to maintain its security. However, this design of the incentive mechanism ignores the joint effect of transaction fees, mint coins and mining duration lengths on the expected mining reward. In this paper, we identify the advanced mining attack that deliberately ignores micro blocks to enlarge the mining duration length to increase the likelihood of winning the mining race. We first show that an advanced mining attacker can maximize its expected reward by optimizing its mining duration length. We then formulate a game-theoretical model in which multiple mining players perform advanced mining to compete with each other. We analyze the Nash equilibrium for the mining game. Our analytical and simulation results indicate that all mining players in the mining game converge to having advanced mining at the equilibrium and have no incentives for deviating from the equilibrium; the transaction processing capability of the Bitcoin-NG network at the equilibrium is decreased by advanced mining. Therefore, we conclude that the Bitcoin-NG blockchain protocol is vulnerable to advanced mining attack. We discuss how to reduce the negative impact of advanced mining for Bitcoin-NG.
A blockchain can be taken as a decentralized and distributed public database. In order to achieve data consistency of the system nodes, the execution of a consensus algorithm is necessary and required in the case of decentralized environments. Simply speaking, the consensus is that every node agrees on some record in the blockchain. There are many kinds of consensus algorithms in blockchain environments, and each consensus algorithm has its own proper application scenario. Here we firstly analysis and compare various popular consensus algorithms in blockchain environments, and then as voting theory has systematically studied the decision-making in a group, the traditional methods of voting theory is summarized and listed, including (Position) scoring rules, Copeland, Maximin, Ranked pairs, Voting trees, Bucklin, Plurality with runoff, Single transferable vote, Baldwin rule, and Nanson rule. Finally, we introduce the voting methods from voting theory to consensus algorithms in the blockchain to improve its performance.
As a distributed system, blockchain is currently an attractive choice for the back-end of public services because of its benefits. Decentralized and carries a consensus mechanism making data stored into irreversible ledger is an advantage of the blockchain. This study discusses the architecture design of academic recording systems in Indonesia, which is currently centralized to be decentralized in permitted networks. Participants involved in the network system, namely institutions as academic staff, teachers, students, and external parties, which each participant has the authority and arrangement with smart-contracts. Evaluation results show less time on the proposed system to complete business processes than the currently system. The task of validation activities can be eliminated and perform smart-contract functions inside to become a "trust-less operation", in which academic data are ensured to be protected from abused or damage due to human error. The data that has been included in the ledger consists of personal performance from the history of academic activities required by students that can be traced by interested parties such as organizations wishing to recruit employees, as well as educational institutions that require the achievement of specific information needed by prospective applicants.
The great increase of the Bitcoin crypto-currency value these last months has brought blockchain and distributed ledger technologies back on the front stage. However, it also gives incentive to malicious users who would like to break the system or take advantage of it (steal money, hide some information stored in the ledger, isolate a particular node from the rest of the network, etc.). Thus, our research focuses on overcoming potential attacks to distributed ledgers. In this paper, we focus on attacks that damage underlying networks of distributed ledgers. Underlying networks offer useful communication primitives such as an atomic broadcast, however such attacks may degrade the property of the primitives and make distributed ledgers relying on the primitives no longer work. Hence we should design algorithms to make the distributed ledgers still work even when some attacks degrade the primitives. As the first study of this problem, we consider distributed ledgers that rely on an atomic broadcast to maintain consistency. We define different cases of attacks affecting the uniform agreement property of the atomic broadcast: We first assume that a single server can fail to deliver a particular message and then we assume that several servers can fail to deliver the message. Afterwards, we present an algorithm to recover the states of the servers that fail to deliver some messages, and consider the situation where the maximum of servers which keep a wrong sequence is known and bounded.