Proceedings of the 1st ACM Conference on Advances in Financial Technologies最新文献

{"title":"An Axiomatic Approach to Block Rewards","authors":"Xi Chen, C. Papadimitriou, T. Roughgarden","doi":"10.1145/3318041.3355470","DOIUrl":"https://doi.org/10.1145/3318041.3355470","url":null,"abstract":"Proof-of-work blockchains reward each miner for one completed block by an amount that is, in expectation, proportional to the number of hashes the miner contributed to the mining of the block. Is this proportional allocation rule optimal? And in what sense? And what other rules are possible? In particular, what are the desirable properties that any \"good\" allocation rule should satisfy? To answer these questions, we embark on an axiomatic theory of incentives in proof-of-work blockchains at the time scale of a single block. We consider desirable properties of allocation rules including: symmetry; budget balance (weak or strong); sybil-proofness; and various grades of collusion-proofness. We show that Bitcoin's proportional allocation rule is the unique allocation rule satisfying a certain system of properties, but this does not hold for slightly weaker sets of properties, or when the miners are not risk-neutral. We also point out that a rich class of allocation rules can be approximately implemented in a proof-of-work blockchain.","PeriodicalId":326009,"journal":{"name":"Proceedings of the 1st ACM Conference on Advances in Financial Technologies","volume":"18 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123517799","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"An Eye for an Eye: Economics of Retaliation in Mining Pools","authors":"Yujin Kwon, Hyoungshick Kim, Yung Yi, Yongdae Kim","doi":"10.1145/3318041.3355472","DOIUrl":"https://doi.org/10.1145/3318041.3355472","url":null,"abstract":"Currently, miners typically join mining pools to solve cryptographic puzzles together, and mining pools are in high competition. This has led to the development of several attack strategies such as block withholding (BWH) and fork after withholding (FAW) attacks that can weaken the health of PoW systems and but maximize mining pools' profits. In this paper, we present strategies called Adaptive Retaliation Strategies (ARS) to mitigate not only BWH attacks but also FAW attacks. In ARS, each pool cooperates with other pools in the normal situation, and adaptively executes either FAW or BWH attacks for the purpose of retaliation only when attacked. In addition, in order for rational pools to adopt ARS, ARS should strike to an adaptive balance between retaliation and selfishness because the pools consider their payoff even when they retaliate. We theoretically and numerically show that ARS would not only lead to the induction of a no-attack state among mining pools, but also achieve the adaptive balance between retaliation and selfishness.","PeriodicalId":326009,"journal":{"name":"Proceedings of the 1st ACM Conference on Advances in Financial Technologies","volume":"147 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123739108","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Quantum Algorithms for Portfolio Optimization","authors":"Iordanis Kerenidis, A. Prakash, Dániel Szilágyi","doi":"10.1145/3318041.3355465","DOIUrl":"https://doi.org/10.1145/3318041.3355465","url":null,"abstract":"We develop the first quantum algorithm for the constrained portfolio optimization problem. The algorithm has running time Õ (n√r ζk/δ2 log (1/ϵ)), where r is the number of positivity and budget constraints, n is the number of assets in the portfolio, ϵ the desired precision, and δ, κ, ζ are problem-dependent parameters related to the well-conditioning of the intermediate solutions. If only a moderately accurate solution is required, our quantum algorithm can achieve a polynomial speedup over the best classical algorithms with complexity Õ (√rnω log(1/ϵ)), where ω is the matrix multiplication exponent that has a theoretical value of around 2.373, but is closer to 3 in practice. We also provide some experiments to bound the problem-dependent factors arising in the running time of the quantum algorithm, and these experiments suggest that for most instances the quantum algorithm can potentially achieve an O(n) speedup over its classical counterpart.","PeriodicalId":326009,"journal":{"name":"Proceedings of the 1st ACM Conference on Advances in Financial Technologies","volume":"17 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116944140","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Spams meet Cryptocurrencies: Sextortion in the Bitcoin Ecosystem","authors":"Masarah Paquet-Clouston, Matteo Romiti, Bernhard Haslhofer, Thomas Charvat","doi":"10.1145/3318041.3355466","DOIUrl":"https://doi.org/10.1145/3318041.3355466","url":null,"abstract":"In the past year, a new spamming scheme has emerged: sexual extortion messages requiring payments in the cryptocurrency Bitcoin, also known as sextortion. This scheme represents a first integration of the use of cryptocurrencies by members of the spamming industry. Using a dataset of 4,340,736 sextortion spams, this research aims at understanding such new amalgamation by uncovering spammers' operations. To do so, a simple, yet effective method for projecting Bitcoin addresses mentioned in sextortion spams onto transaction graph abstractions is computed over the entire Bitcoin blockchain. This allows us to track and investigate monetary flows between involved actors and gain insights into the financial structure of sextortion campaigns. We find that sextortion spammers are somewhat sophisticated, following pricing strategies and benefiting from cost reductions as their operations cut the upper-tail of the spamming supply chain. We discover that one single entity is likely controlling the financial backbone of the majority of the sextortion campaigns and that the 11-month operation studied yielded a lower-bound revenue between $1,300,620 and $1,352,266. We conclude that sextortion spamming is a lucrative business and spammers will likely continue to send bulk emails that try to extort money through cryptocurrencies.","PeriodicalId":326009,"journal":{"name":"Proceedings of the 1st ACM Conference on Advances in Financial Technologies","volume":"21 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-08-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125080215","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Competing (Semi-)Selfish Miners in Bitcoin","authors":"Francisco Javier Marmolejo-Cossío, Eric Brigham, Benjamin Sela, Jonathan Katz","doi":"10.1145/3318041.3355471","DOIUrl":"https://doi.org/10.1145/3318041.3355471","url":null,"abstract":"The Bitcoin protocol prescribes certain behavior by the miners who are responsible for maintaining and extending the underlying blockchain; in particular, miners who successfully solve a puzzle, and hence can extend the chain by a block, are supposed to release that block immediately. Eyal and Sirer showed, however, that a selfish miner is incentivized to deviate from the protocol and withhold its blocks under certain conditions. The analysis by Eyal and Sirer, as well as in followup work, considers a single selfish miner (who may control a large fraction of the hashing power in the network) interacting with a remaining pool of honest miners. Here, we extend this analysis to the case where there are multiple (non-colluding) selfish miners. We find that in this setting there are cases in which it may be profitable for those miners to deviate even when they would not be incentivized to deviate individually.","PeriodicalId":326009,"journal":{"name":"Proceedings of the 1st ACM Conference on Advances in Financial Technologies","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121910896","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Impossibility of Full Decentralization in Permissionless Blockchains","authors":"Yujin Kwon, Jian Liu, Minjeong Kim, D. Song, Yongdae Kim","doi":"10.1145/3318041.3355463","DOIUrl":"https://doi.org/10.1145/3318041.3355463","url":null,"abstract":"Bitcoin uses the proof-of-work (PoW) mechanism where nodes earn rewards in return for the use of their computing resources. Although this incentive system has attracted many participants, power has, at the same time, been significantly biased towards a few nodes, called mining pools. In addition, poor decentralization appears not only in PoW-based coins but also in coins that adopt proof-of-stake (PoS) and delegated proof-of-stake (DPoS) mechanisms. In this paper, we address the issue of centralization in the consensus protocol. To this end, we first define (m, ε, δ)-decentralization as a state satisfying that 1) there are at least m participants running a node, and 2) the ratio between the total resource power of nodes run by the richest and the δ-th percentile participants is less than or equal to 1 + ε. Therefore, when m is sufficiently large, and ε and δ are 0, (m, ε, δ)-decentralization represents full decentralization, which is an ideal state. To ascertain if it is possible to achieve good decentralization, we introduce conditions for an incentive system that will allow a blockchain to achieve (m, ε, δ)-decentralization. When satisfying the conditions, a blockchain system can reach full decentralization with probability 1, regardless of its consensus protocol. However, to achieve this, the blockchain system should be able to assign a positive Sybil cost, where the Sybil cost is defined as the difference between the cost for one participant running multiple nodes and the total cost for multiple participants each running one node. Conversely, we prove that if there is no Sybil cost, the probability of achieving (m, ε, δ)-decentralization is bounded above by a function of fδ, where fδ is the ratio between the resource power of the δ-th percentile and the richest participants. Furthermore, the value of the upper bound is close to 0 for small values of fδ. Considering the current gap between the rich and poor, this result implies that it is almost impossible for a system without Sybil costs to achieve good decentralization. In addition, because it is yet unknown how to assign a Sybil cost without relying on a TTP in blockchains, it also represents that currently, a contradiction between achieving good decentralization in the consensus protocol and not relying on a TTP exists.","PeriodicalId":326009,"journal":{"name":"Proceedings of the 1st ACM Conference on Advances in Financial Technologies","volume":"54 1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-05-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124863002","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"SoK: Consensus in the Age of Blockchains","authors":"S. Bano, A. Sonnino, Mustafa Al-Bassam, Sarah Azouvi, Patrick McCorry, S. Meiklejohn, G. Danezis","doi":"10.1145/3318041.3355458","DOIUrl":"https://doi.org/10.1145/3318041.3355458","url":null,"abstract":"The core technical component of blockchains is consensus: how to reach agreement among a distributed network of nodes. A plethora of blockchain consensus protocols have been proposed---ranging from new designs, to novel modifications and extensions of consensus protocols from the classical distributed systems literature. The inherent complexity of consensus protocols and their rapid and dramatic evolution makes it hard to contextualize the design landscape. We address this challenge by conducting a systematization of knowledge of blockchain consensus protocols. After first discussing key themes in classical consensus protocols, we describe: (i) protocols based on proof-of-work; (ii) proof-of-X protocols that replace proof-of-work with more energy-efficient alternatives; and (iii) hybrid protocols that are compositions or variations of classical consensus protocols. This survey is guided by a systematization framework we develop, to highlight the various building blocks of blockchain consensus design, along with a discussion on their security and performance properties. We identify research gaps and insights for the community to consider in future research endeavours.","PeriodicalId":326009,"journal":{"name":"Proceedings of the 1st ACM Conference on Advances in Financial Technologies","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2017-11-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130023105","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Proceedings of the 1st ACM Conference on Advances in Financial Technologies","authors":"","doi":"10.1145/3318041","DOIUrl":"https://doi.org/10.1145/3318041","url":null,"abstract":"","PeriodicalId":326009,"journal":{"name":"Proceedings of the 1st ACM Conference on Advances in Financial Technologies","volume":"23 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122255818","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}