We introduce economic research on blockchains and its recent advances. In particular, we highlight the (i) unifying concepts on blockchain as a decentralized consensus and its core benefits, (ii) equilibrium characterizations and allegedly irreducible tensions among consensus formation, decentralization, and scalability, (iii) major issues including network security, overconcentration, energy consumption and sustainability, adoption, multi-party computation and encryption, smart contracting, and information distribution and aggregation, and (iv) future directions concerning blockchains and their applications such as informational and agency issues, as well as game-theoretical and mechanism design approaches to blockchain protocols.
Cryptocurrencies employ different consensus protocols to verify transactions. While the Proof-of-Work consensus protocol is the most energy consuming protocol, Proof-of-Stake and Hybrid consensus protocols have been introduced which consume considerably less energy. We employ portfolio analysis to explore whether energy is a fundamental economic factor affecting cryptocurrency prices. Surprisingly, our results suggest that, on average, cryptocurrencies employing Proof-of-Work consensus protocols do not generate returns that are significantly different from those that incorporate Proof-of-Stake consensus protocols. Even more surprising is that our results show that cryptocurrencies that incorporate Hybrid consensus protocols generated significantly higher average return than the other groups. A possible explanation for that phenomenon may be that investors’ demand for cryptocurrencies that they perceive as offering more trust is larger than for those that carry potential risks of blockchain manipulation.
N. Sánchez-Gómez, L. Morales-Trujillo, Jesús Torres Valderrama
Immutability - the ability for a Blockchain (BC) Ledger to remain an unalterable, permanent and indelible \nhistory of transactions - is a feature that is highlighted as a key benefit of BC. This ability is very important \nwhen several companies work collaboratively to achieve common objectives. This collaboration is usually \nrepresented by using business process models. BC is considered as a suitable technology to reduce the \ncomplexity of designing these collaborative processes using Smart Contracts. This paper discusses how to \ncombine Model-based Software Development, modelling techniques, such as use cases models and activity \ndiagram models based on Unified Model Languages (UML) in order to simplify and improve the modelling, \nmanagement and execution of collaborative business processes between multiple companies in the BC \nnetwork. This paper includes the neccessity of using transformation protocols to obtain Smart Contract code. \nIn addition, it presents systematic mechanisms to evaluate and validate Smart Contract, applying early testing \ntechniques, before deploying the Smart Contract code in the BC network.
Soumya Basu, David Easley, Maureen O’Hara, Emin Gün Sirer
Blockchain-based cryptocurrencies prioritize transactions based on their fees, creating a unique kind of fee market. Empirically, this market has failed to yield stable equilibria with predictable prices for desired levels of service. We argue that this is due to the absence of a dominant strategy equilibrium in the current fee mechanism. We propose an alternative fee setting mechanism that is inspired by generalized second price auctions. The design of such a mechanism is challenging because miners can use any criteria for including transactions and can manipulate the results of the auction after seeing the proposed fees. Nonetheless, we show that our proposed protocol is free from manipulation as the number of users increases. We further show that, for a large number of users and miners, the gain from manipulation is small for all parties. This results in users proposing fees that represent their true utility and lower variance of revenue for miners. Historical analysis shows that Bitcoin users could have saved $272,528,000 USD in transaction fees while miners could have reduced the variance of fee income by an average factor of 7.4 times.
Nikhil Malik, Manmohan Aseri, Param Vir Singh, Kannan Srinivasan
Bitcoin falls dramatically short of the scale provided by banks for payments. Currently, its ledger grows by the addition of blocks of ∼2,000 transactions every 10 minutes. Intuitively, one would expect that increasing the block capacity would solve this scaling problem. However, we show that increasing the block capacity would be futile. We analyze strategic interactions of miners, who are heterogeneous in their power over block addition, and users, who are heterogeneous in the value of their transactions, using a game-theoretic model. We show that a capacity increase can facilitate large miners to tacitly collude—artificially reversing back the capacity via strategically adding partially filled blocks in order to extract economic rents. This strategic partial filling crowds out low-value payments. Collusion is sustained if the smallest colluding miner has a share of block addition power above a lower bound. We provide empirical evidence of such strategic partial filling of blocks by large miners of Bitcoin. We show that a protocol design intervention can breach the lower bound and eliminate collusion. However, this also makes the system less secure. On the one hand, collusion crowds out low-value payments; on the other hand, if collusion is suppressed, security threatens high-value payments. As a result, it is untenable to include a range of payments with vastly different outside options, willingness to bear security risk, and delay onto a single chain. Thus, we show economic limits to the scalability of Bitcoin. Under these economic limits, collusive rent extraction acts as an effective mechanism to invest in platform security and build responsiveness to demand shocks. These traits are otherwise hard to attain in a disintermediated setting owing to the high cost of consensus. This paper was accepted by Kartik Hosanagar, information systems.
We present a toolchain for developing and verifying smart contracts that can be executed on Bitcoin. The toolchain is based on BitML, a recent domain-specific language for smart contracts with a computationally sound embedding into Bitcoin. Our toolchain automatically verifies relevant properties of contracts, among which liquidity, ensuring that funds do not remain frozen within a contract forever. A compiler is provided to translate BitML contracts into sets of standard Bitcoin transactions: executing a contract corresponds to appending these transactions to the blockchain. We assess our toolchain through a benchmark of representative contracts.
Efficient transfers to many recipients present a host of issues on Ethereum. First, accounts are identified by long and incompressible constants. Second, these constants have to be stored and communicated for each payment. Third, the standard interface for token transfers does not support lists of recipients, adding repeated communication to the overhead. Since Ethereum charges resource usage, even small optimizations translate to cost savings. Airdrops, a popular marketing tool used to boost coin uptake, present a relevant example for the value of optimizing bulk transfers. Therefore, we review technical solutions for airdrops of Ethereum-based tokens, discuss features and prerequisites, and compare the operational costs by simulating 35 scenarios. We find that cost savings of factor two are possible, but require specific provisions in the smart contract implementing the token system. Pull-based approaches, which use on-chain interaction with the recipients, promise moderate savings for the distributor while imposing a disproportional cost on each recipient. Total costs are broadly linear in the number of recipients independent of the technical approach. We publish the code of the simulation framework for reproducibility, to support future airdrop decisions, and to benchmark innovative bulk payment solutions.
И.И. Баринов, Vadim Arasev, Andreas Fackler, Vladimir Komendantskiy · 7 authors
In this paper we introduce POSDAO, a Proof of Stake (POS) algorithm implemented as a decentralized autonomous organization (DAO). It is designed to provide a decentralized, fair, and energy efficient consensus for public chains. The algorithm works as a set of smart contracts written in Solidity. POSDAO is implemented with a general purpose BFT consensus protocol such as Authority Round (AuRa) with a proposer node and probabilistic finality, or Honey Badger BFT (HBBFT), leaderless and with instant finality. Validators are incentivized to behave in the best interests of a network through a configurable reward structure. The algorithm provides a Sybil control mechanism for managing a set of validators, distributing rewards, and reporting and penalizing malicious validators. The authors provide a reference POSDAO implementation, xDai POSDAO, which uses xDai as a stable transactional coin and a representative ERC677 token (STAKE) as a staking token. The reference implementation functions on an Ethereum 1.0 sidechain and utilizes the AuRa consensus protocol. Assets are bridged between the Ethereum mainnet and the xDai POSDAO network using several instances of the POA TokenBridge.
Over the past decade, blockchain technology has attracted tremendous attention from both academia and industry. The popularity of blockchains was originated from the concept of crypto-currencies to serve as a decentralized and tamper-proof transaction data ledger. Nowadays, blockchains as the key framework in the decentralized public data-ledger have been applied to a wide range of scenarios far beyond crypto-currencies, such as the Internet of Things, healthcare, and insurance. This survey aims to fill the gap between a large number of studies on blockchain networks, where game theory emerges as an analytical tool, and the lack of a comprehensive survey on the game theoretical approaches applied in blockchain-related issues. In this survey, we review the game models proposed to address common issues in the blockchain network. The focus is placed on security issues, e.g., selfish mining, majority attack and denial of service attack, issues regarding mining management, e.g., computational power allocation, reward allocation, and pool selection, as well as issues regarding blockchain economic and energy trading. Additionally, we discuss the advantages and disadvantages of these selected game theoretical models and solutions. Finally, we highlight important challenges and future research directions of applying game theoretical approaches to incentive mechanism design and the combination of blockchain with other technologies.
One of the purported benefits of blockchain technologies is the ability to house what have been termed ‘smart’ contracts. Such contracts are potentially self-executing depending on the state of information recorded on a blockchain ledger. This paper examines the capabilities of smart contracts from an economic perspective. It is demonstrated that by improving observability and reducing the costs of verification of contract obligation performance, the space of feasible contracts can be enlarged. Moreover, by providing commitments to various monetary payments, a blockchain can potentially create a foundation to house certain mechanisms that have been shown to overcome difficulties of contractual incompleteness. This is demonstrated using a simple international trade environment. Thus, even though smart contracts must respect the incentives of decision-makers in their obligations, they have the potential to use easily verifiable elements to create incentives to reduce hold-up and other contractual difficulties.
We use historical data to estimate the potential benefit of speculative techniques for executing Ethereum smart contracts in parallel. We replay transaction traces of sampled blocks from the Ethereum blockchain over time, using a simple speculative execution engine. In this engine, miners attempt to execute all transactions in a block in parallel, rolling back those that cause data conflicts. Aborted transactions are then executed sequentially. Validators execute the same schedule as miners. \nWe find that our speculative technique yields estimated speed-ups starting at about 8-fold in 2016, declining to about 2-fold at the end of 2017, where speed-up is measured using either gas costs or instruction counts. We also observe that a small set of contracts are responsible for many data conflicts resulting from speculative concurrent execution.
In this work, we perform a comprehensive empirical study of smart contracts deployed on the ethereum blockchain. The objective of the analysis is to provide empirical results on smart contracts features, smart contract transactions within the blockchain, the role of the development community, and the source code characteristics. We collected a set of more than 10000 smart contracts source codes and a dataset of meta-data regarding their interaction with the blockchain from etherscan.io. We examined the collected data computing different statistics on naming policies, smart contract ether balance, number of smart contract transactions, functions, and other quantities characterizing the use and purpose of smart contracts. We found that the number of transactions and the balances follow power-law distributions and the software code metrics display, on average, values lower than corresponding metrics in standard software but have high variances. Focusing the attention on the 20 smart contracts with the topmost number of transactions, we found that most of them represent financial smart contracts and some of them have peculiar software development stories behind them. The results show that blockchain software is rapidly changing and evolving and it is no longer devoted only to cryptovalues applications but to general purpose computation.
In this paper, we present the most extensive evaluation of blockchain system to date. To achieve scalability across servers in more than 10 countries located on 4 different continents, we drastically revisited Byzantine fault tolerant blockchains and verification of signatures. The resulting blockchain, called the Red Belly Blockchain (RBBC), commits more than a hundred thousand transactions issued by permissionless nodes. These transactions are grouped into blocks within few seconds through a partially synchronous consensus run by permissioned nodes. It prevents double spending by guaranteeing that a unique block is decided at any given index of the chain in a deterministic way by all participants. We compared the performance of RBBC against traditional Byzantine fault tolerant alternatives and more recent randomized solutions. In the same geo-distributed environment with low-end machines, we noticed two interesting comparisons: (i) the RBBC throughput scales to hundreds of machines whereas the classic 3-step leader-based BFT state machine used by consortium blockchains cannot scale to 40 identically configured nodes; (ii) RBBC guarantees transaction finality in 3 seconds and experiences a third of the latency that randomized-based solutions like HoneyBadgerBFT can offer. This empirical evaluation demonstrates that blockchain scalability can be achieved without sacrificing security.
Cryptocurrency blockchain technology is attracting worldwide attention, and the number of initial coin offerings (ICOs) is increasing rapidly. This new economic trend, called cryptoeconomics, can program human behavior through incentive design. A cryptocurrency-based incentive system is not only transparent, but also allows businesses to substitute initial investment costs with cryptocurrency tokens until they are on a sustainable growth trajectory in terms of network effects. This study aims to propose a process for building a desirable model of a token economy, based on the case of Steemit—a blogging and social networking website that is creating high values due to its efficient token economy model. We suggest the following design process of a token economy model: (1) Determine token-business fit, (2) determine the chance of success, (3) determine the properties of token, (4) give tokens intrinsic value, (5) establish strategies to raise token value, (6) establish operational strategies of token economy system, (7) establish strategies for token liquidation, and (8) continue modifying the operational base. Considering cryptoeconomics is still at an early stage, it is expected that the guidelines on the token economy model suggested in this paper will lay a significant foundation for the development of cryptoeconomics research.
We present SOLAR, a new analysis tool for automatically detecting standard violation errors in Ethereum smart contracts.Given the Ethereum Virtual Machine (EVM) bytecode of a smart contract and a user specified constraint or invariant derived from a technical standard such as ERC-20,SOLAR symbolically executes the contract, explores all possible execution paths, and checks whether it is possible to initiate a sequence of malicious transactions to violate the specified constraint or invariant. Our experimental results highlight the effectiveness of SOLAR in finding new errors in smart con-tracts. Out of the evaluated 779 ERC-20 and 310 ERC-721smart contracts, SOLAR found 255 standard violation errors in 197 vulnerable contracts with only three false positives.237 out of the 255 errors are zero-day errors that are not re-ported before. Our results sound the alarm on the prevalence of standard violation errors in critical smart contracts that manipulate publicly traded digital assets
The fundamental problem in digital record-keeping is establishing consensus on an update to a ledger, e.g., a payment. Consensus must be achieved in the presence of faults-situations in which some computers are offline or fail to function appropriately. Traditional centralized record-keeping systems rely on trust in a single entity to achieve consensus. Blockchains decentralize record-keeping, dispensing with the need for trust in a single entity, but some instead build a consensus based on the wasteful expenditure of computational resources (proof-of-work). An ideal method of consensus would be tolerant to faults, avoid the waste of computational resources, and be capable of implementing all individually rational transfers of value among agents. We prove a Blockchain Trilemma: any method of consensus, be it centralized or decentralized, must give up (i) fault-tolerance, (ii) resource-efficiency, or (iii) full transferability.