Asymmetric Proof-Of-Work Based on the Generalized Birthday Problem
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Chia Proof of Space Construction
Chia Proof of Space Construction Introduction In order to create a secure blockchain consensus algorithm using disk space, a Proof of Space is scheme is necessary. This document describes a practical contruction of Proofs of Space, based on Beyond Hellman’s Time- Memory Trade-Offs with Applications to Proofs of Space [1]. We use the techniques laid out in that paper, extend it from 2 to 7 tables, and tweak it to make it efficient and secure, for use in the Chia Blockchain. The document is divided into three main sections: What (mathematical definition of a proof of space), How (how to implement proof of space), and Why (motivation and explanation of the construction) sections. The Beyond Hellman paper can be read first for more mathematical background. Chia Proof of Space Construction Introduction What is Proof of Space? Definitions Proof format Proof Quality String Definition of parameters, and M, f, A, C functions: Parameters: f functions: Matching function M: A′ function: At function: Collation function C: How do we implement Proof of Space? Plotting Plotting Tables (Concepts) Tables Table Positions Compressing Entry Data Delta Format ANS Encoding of Delta Formatted Points Stub and Small Deltas Parks Checkpoint Tables Plotting Algorithm Final Disk Format Full algorithm Phase 1: Forward Propagation Phase 2: Backpropagation Phase 3: Compression Phase 4: Checkpoints Sort on Disk Plotting Performance Space Required Proving Proof ordering vs Plot ordering Proof Retrieval Quality String Retrieval Proving Performance Verification Construction -
Virtual Currencies and Terrorist Financing : Assessing the Risks And
DIRECTORATE GENERAL FOR INTERNAL POLICIES POLICY DEPARTMENT FOR CITIZENS' RIGHTS AND CONSTITUTIONAL AFFAIRS COUNTER-TERRORISM Virtual currencies and terrorist financing: assessing the risks and evaluating responses STUDY Abstract This study, commissioned by the European Parliament’s Policy Department for Citizens’ Rights and Constitutional Affairs at the request of the TERR Committee, explores the terrorist financing (TF) risks of virtual currencies (VCs), including cryptocurrencies such as Bitcoin. It describes the features of VCs that present TF risks, and reviews the open source literature on terrorist use of virtual currencies to understand the current state and likely future manifestation of the risk. It then reviews the regulatory and law enforcement response in the EU and beyond, assessing the effectiveness of measures taken to date. Finally, it provides recommendations for EU policymakers and other relevant stakeholders for ensuring the TF risks of VCs are adequately mitigated. PE 604.970 EN ABOUT THE PUBLICATION This research paper was requested by the European Parliament's Special Committee on Terrorism and was commissioned, overseen and published by the Policy Department for Citizens’ Rights and Constitutional Affairs. Policy Departments provide independent expertise, both in-house and externally, to support European Parliament committees and other parliamentary bodies in shaping legislation and exercising democratic scrutiny over EU external and internal policies. To contact the Policy Department for Citizens’ Rights and Constitutional Affairs or to subscribe to its newsletter please write to: [email protected] RESPONSIBLE RESEARCH ADMINISTRATOR Kristiina MILT Policy Department for Citizens' Rights and Constitutional Affairs European Parliament B-1047 Brussels E-mail: [email protected] AUTHORS Tom KEATINGE, Director of the Centre for Financial Crime and Security Studies, Royal United Services Institute (coordinator) David CARLISLE, Centre for Financial Crime and Security Studies, Royal United Services Institute, etc. -
Characterizing Ethereum's Mining Power Decentralization at a Deeper
Characterizing Ethereum’s Mining Power Decentralization at a Deeper Level Liyi Zeng∗§, Yang Chen†§, Shuo Chen†, Xian Zhang†, Zhongxin Guo†, Wei Xu∗, Thomas Moscibroda‡ ∗Institute for Interdisciplinary Information Sciences, Tsinghua University †Microsoft Research ‡Microsoft Azure §Contacts: [email protected], [email protected] Abstract—For proof-of-work blockchains such as Ethereum, than 50% of the total power has grown from several the mining power decentralization is an important discussion hundred to several thousand. Overall, the power is more point in the community. Previous studies mostly focus on the decentralized at the participant level than 4 years ago. aggregated power of the mining pools, neglecting the pool participants who are the source of the pools’ power. In this paper, However, we also find that this number varied signif- we present the first large-scale study of the pool participants icantly over time, which means it requires continuous in Ethereum’s mining pools. Pool participants are not directly tracking. Additionally, as our current data and method- observable because they communicate with their pools via private ology cannot de-anonymize the participants, it’s possible channels. However, they leave “footprints” on chain as they that some participants split themselves into many smaller use Ethereum accounts to anonymously receive rewards from mining pools. For this study, we combine several data sources ones for various reasons, which could make our estima- to identify 62,358,646 pool reward transactions sent by 47 tion inaccurate if not completely off the target. Further pools to their participants over Ethereum’s entire near 5-year study to improve the estimation accuracy is important. -
Crypto Research Report ‒ April 2019 Edition
April 2019 Edition VI. “When the Tide Goes Out…” Investments: Gold and Bitcoin, Stronger Together Technical Analysis: Spring Awakening? Cryptocurrency Mining in Theory and Practice Demelza Kelso Hays Mark J. Valek We would like to express our profound gratitude to our premium partners for supporting the Crypto Research Report: www.cryptofunds.li Contents Editorial ............................................................................................................................................... 4 In Case You Were Sleeping: When the Tide Goes Out…............................................................... 5 Back to the Roots ............................................................................................................................................. 6 How Long Will This Bear Market Last .............................................................................................................. 7 A Tragic Story Traverses the World ................................................................................................................. 9 When the tide goes out… ............................................................................................................................... 10 A State Cryptocurrency? ................................................................................................................................ 12 Support is Increasing ..................................................................................................................................... 14 -
Beauty Is Not in the Eye of the Beholder
Insight Consumer and Wealth Management Digital Assets: Beauty Is Not in the Eye of the Beholder Parsing the Beauty from the Beast. Investment Strategy Group | June 2021 Sharmin Mossavar-Rahmani Chief Investment Officer Investment Strategy Group Goldman Sachs The co-authors give special thanks to: Farshid Asl Managing Director Matheus Dibo Shahz Khatri Vice President Vice President Brett Nelson Managing Director Michael Murdoch Vice President Jakub Duda Shep Moore-Berg Harm Zebregs Vice President Vice President Vice President Shivani Gupta Analyst Oussama Fatri Yousra Zerouali Vice President Analyst ISG material represents the views of ISG in Consumer and Wealth Management (“CWM”) of GS. It is not financial research or a product of GS Global Investment Research (“GIR”) and may vary significantly from those expressed by individual portfolio management teams within CWM, or other groups at Goldman Sachs. 2021 INSIGHT Dear Clients, There has been enormous change in the world of cryptocurrencies and blockchain technology since we first wrote about it in 2017. The number of cryptocurrencies has increased from about 2,000, with a market capitalization of over $200 billion in late 2017, to over 8,000, with a market capitalization of about $1.6 trillion. For context, the market capitalization of global equities is about $110 trillion, that of the S&P 500 stocks is $35 trillion and that of US Treasuries is $22 trillion. Reported trading volume in cryptocurrencies, as represented by the two largest cryptocurrencies by market capitalization, has increased sixfold, from an estimated $6.8 billion per day in late 2017 to $48.6 billion per day in May 2021.1 This data is based on what is called “clean data” from Coin Metrics; the total reported trading volume is significantly higher, but much of it is artificially inflated.2,3 For context, trading volume on US equity exchanges doubled over the same period. -
IPFS and Friends: a Qualitative Comparison of Next Generation Peer-To-Peer Data Networks Erik Daniel and Florian Tschorsch
1 IPFS and Friends: A Qualitative Comparison of Next Generation Peer-to-Peer Data Networks Erik Daniel and Florian Tschorsch Abstract—Decentralized, distributed storage offers a way to types of files [1]. Napster and Gnutella marked the beginning reduce the impact of data silos as often fostered by centralized and were followed by many other P2P networks focusing on cloud storage. While the intentions of this trend are not new, the specialized application areas or novel network structures. For topic gained traction due to technological advancements, most notably blockchain networks. As a consequence, we observe that example, Freenet [2] realizes anonymous storage and retrieval. a new generation of peer-to-peer data networks emerges. In this Chord [3], CAN [4], and Pastry [5] provide protocols to survey paper, we therefore provide a technical overview of the maintain a structured overlay network topology. In particular, next generation data networks. We use select data networks to BitTorrent [6] received a lot of attention from both users and introduce general concepts and to emphasize new developments. the research community. BitTorrent introduced an incentive Specifically, we provide a deeper outline of the Interplanetary File System and a general overview of Swarm, the Hypercore Pro- mechanism to achieve Pareto efficiency, trying to improve tocol, SAFE, Storj, and Arweave. We identify common building network utilization achieving a higher level of robustness. We blocks and provide a qualitative comparison. From the overview, consider networks such as Napster, Gnutella, Freenet, BitTor- we derive future challenges and research goals concerning data rent, and many more as first generation P2P data networks, networks. -
Evaluating Inclusion, Equality, Security, and Privacy in Pseudonym Parties and Other Proofs of Personhood
Identity and Personhood in Digital Democracy: Evaluating Inclusion, Equality, Security, and Privacy in Pseudonym Parties and Other Proofs of Personhood Bryan Ford Swiss Federal Institute of Technology in Lausanne (EPFL) November 5, 2020 Abstract of enforced physical security and privacy can address the coercion and vote-buying risks that plague today’s E- Digital identity seems at first like a prerequisite for digi- voting and postal voting systems alike. We also examine tal democracy: how can we ensure “one person, one vote” other recently-proposed approaches to proof of person- online without identifying voters? But the full gamut of hood, some of which offer conveniencessuch as all-online digital identity solutions – e.g., online ID checking, bio- participation. These alternatives currently fall short of sat- metrics, self-sovereign identity, and social/trust networks isfying all the key digital personhood goals, unfortunately, – all present severe flaws in security, privacy, and trans- but offer valuable insights into the challenges we face. parency, leaving users vulnerable to exclusion, identity loss or theft, and coercion. These flaws may be insur- mountable because digital identity is a cart pulling the Contents horse. We cannot achieve digital identity secure enough to support the weight of digital democracy, until we can 1 Introduction 2 build it on a solid foundation of digital personhood meet- ing key requirements. While identity is about distinguish- 2 Goals for Digital Personhood 4 ing one person from another through attributes or affilia- tions, personhood is about giving all real people inalien- 3 Pseudonym Parties 5 able digital participation rights independent of identity, 3.1 Thebasicidea. -
Banking on Bitcoin: BTC As Collateral
Banking on Bitcoin: BTC as Collateral Arcane Research Bitstamp Arcane Research is a part of Arcane Crypto, Bitstamp is the world’s longest-running bringing data-driven analysis and research cryptocurrency exchange, supporting to the cryptocurrency space. After launch in investors, traders and leading financial August 2019, Arcane Research has become institutions since 2011. With a proven track a trusted brand, helping clients strengthen record, cutting-edge market infrastructure their credibility and visibility through and dedication to personal service with a research reports and analysis. In addition, human touch, Bitstamp’s secure and reliable we regularly publish reports, weekly market trading venue is trusted by over four million updates and articles to educate and share customers worldwide. Whether it’s through insights. their intuitive web platform and mobile app or industry-leading APIs, Bitstamp is where crypto enters the world of finance. For more information, visit www.bitstamp.net 2 Banking on Bitcoin: BTC as Collateral Banking on bitcoin The case for bitcoin as collateral The value of the global market for collateral is estimated to be close to $20 trillion in assets. Government bonds and cash-based securities alike are currently the most important parts of a well- functioning collateral market. However, in that, there is a growing weakness as rehypothecation creates a systemic risk in the financial system as a whole. The increasing reuse of collateral makes these assets far from risk-free and shows the potential instability of the financial markets and that it is more fragile than many would like to admit. Bitcoin could become an important part of the solution and challenge the dominating collateral assets in the future. -
Zcash Protocol Speci Cation
Zcash Protocol Specication Version 2018.0-beta-14 Daira Hopwood† Sean Bowe† — Taylor Hornby† — Nathan Wilcox† March 11, 2018 Abstract. Zcash is an implementation of the Decentralized Anonymous Payment scheme Zerocash, with security xes and adjustments to terminology, functionality and performance. It bridges the exist- ing transparent payment scheme used by Bitcoin with a shielded payment scheme secured by zero- knowledge succinct non-interactive arguments of knowledge (zk-SNARKs). It attempts to address the problem of mining centralization by use of the Equihash memory-hard proof-of-work algorithm. This specication denes the Zcash consensus protocol and explains its differences from Zerocash and Bitcoin. Keywords: anonymity, applications, cryptographic protocols, electronic commerce and payment, nancial privacy, proof of work, zero knowledge. Contents 1 1 Introduction 5 1.1 Caution . .5 1.2 High-level Overview . .5 2 Notation 7 3 Concepts 8 3.1 Payment Addresses and Keys . .8 3.2 Notes...........................................................9 3.2.1 Note Plaintexts and Memo Fields . .9 3.3 The Block Chain . 10 3.4 Transactions and Treestates . 10 3.5 JoinSplit Transfers and Descriptions . 11 3.6 Note Commitment Trees . 11 3.7 Nullier Sets . 12 3.8 Block Subsidy and Founders’ Reward . 12 3.9 Coinbase Transactions . 12 † Zerocoin Electric Coin Company 1 4 Abstract Protocol 12 4.1 Abstract Cryptographic Schemes . 12 4.1.1 Hash Functions . 12 4.1.2 Pseudo Random Functions . 13 4.1.3 Authenticated One-Time Symmetric Encryption . 13 4.1.4 Key Agreement . 13 4.1.5 Key Derivation . 14 4.1.6 Signature . 15 4.1.6.1 Signature with Re-Randomizable Keys . -
Piecework: Generalized Outsourcing Control for Proofs of Work
(Short Paper): PieceWork: Generalized Outsourcing Control for Proofs of Work Philip Daian1, Ittay Eyal1, Ari Juels2, and Emin G¨unSirer1 1 Department of Computer Science, Cornell University, [email protected],[email protected],[email protected] 2 Jacobs Technion-Cornell Institute, Cornell Tech [email protected] Abstract. Most prominent cryptocurrencies utilize proof of work (PoW) to secure their operation, yet PoW suffers from two key undesirable prop- erties. First, the work done is generally wasted, not useful for anything but the gleaned security of the cryptocurrency. Second, PoW is natu- rally outsourceable, leading to inegalitarian concentration of power in the hands of few so-called pools that command large portions of the system's computation power. We introduce a general approach to constructing PoW called PieceWork that tackles both issues. In essence, PieceWork allows for a configurable fraction of PoW computation to be outsourced to workers. Its controlled outsourcing allows for reusing the work towards additional goals such as spam prevention and DoS mitigation, thereby reducing PoW waste. Meanwhile, PieceWork can be tuned to prevent excessive outsourcing. Doing so causes pool operation to be significantly more costly than today. This disincentivizes aggregation of work in mining pools. 1 Introduction Distributed cryptocurrencies such as Bitcoin [18] rely on the equivalence \com- putation = money." To generate a batch of coins, clients in a distributed cryp- tocurrency system perform an operation called mining. Mining requires solving a computationally intensive problem involving repeated cryptographic hashing. Such problem and its solution is called a Proof of Work (PoW) [11]. As currently designed, nearly all PoWs suffer from one of two drawbacks (or both, as in Bitcoin). -
Short Selling Attack: a Self-Destructive but Profitable 51% Attack on Pos Blockchains
Short Selling Attack: A Self-Destructive But Profitable 51% Attack On PoS Blockchains Suhyeon Lee and Seungjoo Kim CIST (Center for Information Security Technologies), Korea University, Korea Abstract—There have been several 51% attacks on Proof-of- With a PoS, the attacker needs to obtain 51% of the Work (PoW) blockchains recently, including Verge and Game- cryptocurrency to carry out a 51% attack. But unlike PoW, Credits, but the most noteworthy has been the attack that saw attacker in a PoS system is highly discouraged from launching hackers make off with up to $18 million after a successful double spend was executed on the Bitcoin Gold network. For this reason, 51% attack because he would have to risk of depreciation the Proof-of-Stake (PoS) algorithm, which already has advantages of his entire stake amount to do so. In comparison, bad of energy efficiency and throughput, is attracting attention as an actor in a PoW system will not lose their expensive alternative to the PoW algorithm. With a PoS, the attacker needs mining equipment if he launch a 51% attack. Moreover, to obtain 51% of the cryptocurrency to carry out a 51% attack. even if a 51% attack succeeds, the value of PoS-based But unlike PoW, attacker in a PoS system is highly discouraged from launching 51% attack because he would have to risk losing cryptocurrency will fall, and the attacker with the most stake his entire stake amount to do so. Moreover, even if a 51% attack will eventually lose the most. For these reasons, those who succeeds, the value of PoS-based cryptocurrency will fall, and attempt to attack 51% of the PoS blockchain will not be the attacker with the most stake will eventually lose the most. -
Understanding the Motivations, Challenges and Needs of Blockchain Software Developers: a Survey
Empirical Software Engineering manuscript No. (will be inserted by the editor) Understanding the Motivations, Challenges and Needs of Blockchain Software Developers: A Survey Amiangshu Bosu · Anindya Iqbal · Rifat Shahriyar · Partha Chakroborty Received: November 6, 2018 / Accepted: March 19, 2019 Abstract The blockchain technology has potential applications in various areas such as smart-contracts, Internet of Things (IoT), land registry, supply chain man- agement, storing medical data, and identity management. Although the Github currently hosts more than six thousand active Blockchain software (BCS) projects, few software engineering research has investigated these projects and its' contrib- utors. Although the number of BCS projects is growing rapidly, the motivations, challenges, and needs of BCS developers remain a puzzle. Therefore, the primary objective of this study is to understand the motivations, challenges, and needs of BCS developers and analyze the differences between BCS and non-BCS development. On this goal, we sent an online survey to 1,604 active BCS developers identified via mining the Github repositories of 145 popular BCS projects. The survey received 156 responses that met our criteria for analysis. The results suggest that the majority of the BCS developers are experienced in non-BCS development and are primarily motivated by the ideology of creating a decentralized financial system. Although most of the BCS projects are Open Source Software (OSS) projects by nature, more than 93% of our respondents found BCS development somewhat different from a non-BCS development as BCS projects have higher emphasis on security and reliability than most of the non- BCS projects. Other differences include: higher costs of defects, decentralized and hostile environment, technological complexity, and difficulty in upgrading the soft- ware after release.