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Auditing Wallets in Cryptonote
Auditing wallets in CryptoNote sowle <[email protected]> Zano project, https://zano.org Cryptocurrency wallet auditing is the ability for a third party (the "auditor") to watch the transactions and to be able to calculate the correct balance without an ability to spend a coin. This article explores several possible implementations of expansion cryptocurrency protocol CryptoNote 2.0 [1] with such ability. In the original CryptoNote protocol auditing is only partially possible with the help of the tracking key, namely, an auditor is able to distinguish incoming transactions in the blockchain, but the full set of secret keys is required to filter out outgoing transactions. This article is intended for readers familiar with the general blockchain technology and “classic” cryptocurrencies, as well as with the basics of cryptography on elliptic curves. 1. Introduction What is CryptoNote? Surprisingly, most people interested in blockchain technology have never heard anything about CryptoNote, in spite of the fact that the technology has more than 300 forks, including Monero as the most famous. Back in 2014 in the cryptocurrency community there were mentions [2] about a project, titled Bytecoin. That project did not originate as a Bitcoin or other known project fork, having its own original codebase. It was very unusual at the time. Bytecoin general conception was to be an implementation of a privacy-technology named CryptoNote. There were two main privacy mechanisms: stealth-addresses and inputs` mixing-in with the help of ring signatures (at the time it was called "blockchain mixer"). Since Zcash existed only on paper / in theory at that time, CryptoNote became a competitive technology and has provoked much controversy in the cryptocurrency community. -
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 -
Asymmetric Proof-Of-Work Based on the Generalized Birthday Problem
Equihash: Asymmetric Proof-of-Work Based on the Generalized Birthday Problem Alex Biryukov Dmitry Khovratovich University of Luxembourg University of Luxembourg [email protected] [email protected] Abstract—The proof-of-work is a central concept in modern Long before the rise of Bitcoin it was realized [20] that cryptocurrencies and denial-of-service protection tools, but the the dedicated hardware can produce a proof-of-work much requirement for fast verification so far made it an easy prey for faster and cheaper than a regular desktop or laptop. Thus the GPU-, ASIC-, and botnet-equipped users. The attempts to rely on users equipped with such hardware have an advantage over memory-intensive computations in order to remedy the disparity others, which eventually led the Bitcoin mining to concentrate between architectures have resulted in slow or broken schemes. in a few hardware farms of enormous size and high electricity In this paper we solve this open problem and show how to consumption. An advantage of the same order of magnitude construct an asymmetric proof-of-work (PoW) based on a compu- is given to “owners” of large botnets, which nowadays often tationally hard problem, which requires a lot of memory to gen- accommodate hundreds of thousands of machines. For prac- erate a proof (called ”memory-hardness” feature) but is instant tical DoS protection, this means that the early TLS puzzle to verify. Our primary proposal Equihash is a PoW based on the schemes [8], [17] are no longer effective against the most generalized birthday problem and enhanced Wagner’s algorithm powerful adversaries. -
Vulnerability of Blockchain Technologies to Quantum Attacks
Vulnerability of Blockchain Technologies to Quantum Attacks Joseph J. Kearneya, Carlos A. Perez-Delgado a,∗ aSchool of Computing, University of Kent, Canterbury, Kent CT2 7NF United Kingdom Abstract Quantum computation represents a threat to many cryptographic protocols in operation today. It has been estimated that by 2035, there will exist a quantum computer capable of breaking the vital cryptographic scheme RSA2048. Blockchain technologies rely on cryptographic protocols for many of their essential sub- routines. Some of these protocols, but not all, are open to quantum attacks. Here we analyze the major blockchain-based cryptocurrencies deployed today—including Bitcoin, Ethereum, Litecoin and ZCash, and determine their risk exposure to quantum attacks. We finish with a comparative analysis of the studied cryptocurrencies and their underlying blockchain technologies and their relative levels of vulnerability to quantum attacks. Introduction exist to allow the legitimate owner to recover this account. Blockchain systems are unlike other cryptosys- tems in that they are not just meant to protect an By contrast, in a blockchain system, there is no information asset. A blockchain is a ledger, and as central authority to manage users’ access keys. The such it is the asset. owner of a resource is by definition the one hold- A blockchain is secured through the use of cryp- ing the private encryption keys. There are no of- tographic techniques. Notably, asymmetric encryp- fline backups. The blockchain, an always online tion schemes such as RSA or Elliptic Curve (EC) cryptographic system, is considered the resource— cryptography are used to generate private/public or at least the authoritative description of it. -
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 . -
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. -
Hybrid Public/Anonymous Transactions on Monero, Cryptonote X-Cash
Hybrid public/anonymous transactions on Monero, Cryptonote X-Cash Zach Hildreth October 7, 2019 Abstract This yellow paper details the technical concepts and implementation of hybrid transactions (also known as FlexPrivacy c ), a feature enabling public and private transactions on the X- Cash public blockchain. In the first part, the paper aims at detailing how the hybrid transactions operate from a user’s perspective with some real-world use cases. A parallel is made between the digital money system and the economic behaviors associated with the current FIAT system. Secondly, a deeper understanding of the technology is given, explaining the implication on a blockchain perspective, as well as the edge cases and their approaches. Lastly, the last part consists in an in-depth approach of the mathematical concepts and technical implementation of the hybrid transaction in the X-Cash blockchain. Contents 1 Public transactions in the ringCT 4 2 Privacy in the inputs 4 3 A brief understanding of cryptonote transactions 4 4 Creation of a public address 6 5 How stealth addresses/outputs are decoded 6 6 How public transactions are created 7 1 Summary of the public transaction feature The hybrid transaction feature allows users to send and receive public or private transactions on the X-Network Blockchain X-Cash, which is based on the CryptoNote protocol. This feature is implemented on a per transaction basis where users can directly switch the privacy type by choosing the setting before attempting to send a transaction. In a public transaction, the following additional information is made public: • Sender’s address • Receiver’s address • Amount sent • Change amount sent back to the sender’s address However, the public transaction does not compromise the sender’s or receiver’s wallet full bal- ances nor the real mixin (number of signatures in the ring signature that authorizes the transaction) that provided the X-Cash balance. -
Coinbase Explores Crypto ETF (9/6) Coinbase Spoke to Asset Manager Blackrock About Creating a Crypto ETF, Business Insider Reports
Crypto Week in Review (9/1-9/7) Goldman Sachs CFO Denies Crypto Strategy Shift (9/6) GS CFO Marty Chavez addressed claims from an unsubstantiated report earlier this week that the firm may be delaying previous plans to open a crypto trading desk, calling the report “fake news”. Coinbase Explores Crypto ETF (9/6) Coinbase spoke to asset manager BlackRock about creating a crypto ETF, Business Insider reports. While the current status of the discussions is unclear, BlackRock is said to have “no interest in being a crypto fund issuer,” and SEC approval in the near term remains uncertain. Looking ahead, the Wednesday confirmation of Trump nominee Elad Roisman has the potential to tip the scales towards a more favorable cryptoasset approach. Twitter CEO Comments on Blockchain (9/5) Twitter CEO Jack Dorsey, speaking in a congressional hearing, indicated that blockchain technology could prove useful for “distributed trust and distributed enforcement.” The platform, given its struggles with how best to address fraud, harassment, and other misuse, could be a prime testing ground for decentralized identity solutions. Ripio Facilitates Peer-to-Peer Loans (9/5) Ripio began to facilitate blockchain powered peer-to-peer loans, available to wallet users in Argentina, Mexico, and Brazil. The loans, which utilize the Ripple Credit Network (RCN) token, are funded in RCN and dispensed to users in fiat through a network of local partners. Since all details of the loan and payments are recorded on the Ethereum blockchain, the solution could contribute to wider access to credit for the unbanked. IBM’s Payment Protocol Out of Beta (9/4) Blockchain World Wire, a global blockchain based payments network by IBM, is out of beta, CoinDesk reports. -
Impossibility of Full Decentralization in Permissionless Blockchains
Impossibility of Full Decentralization in Permissionless Blockchains Yujin Kwon*, Jian Liuy, Minjeong Kim*, Dawn Songy, Yongdae Kim* *KAIST {dbwls8724,mjkim9394,yongdaek}@kaist.ac.kr yUC Berkeley [email protected],[email protected] ABSTRACT between achieving good decentralization in the consensus protocol Bitcoin uses the proof-of-work (PoW) mechanism where nodes earn and not relying on a TTP exists. rewards in return for the use of their computing resources. Although this incentive system has attracted many participants, power has, CCS CONCEPTS at the same time, been significantly biased towards a few nodes, • Security and privacy → Economics of security and privacy; called mining pools. In addition, poor decentralization appears not Distributed systems security; only in PoW-based coins but also in coins that adopt proof-of-stake (PoS) and delegated proof-of-stake (DPoS) mechanisms. KEYWORDS In this paper, we address the issue of centralization in the consen- Blockchain; Consensus Protocol; Decentralization sus protocol. To this end, we first define ¹m; ε; δº-decentralization as a state satisfying that 1) there are at least m participants running 1 INTRODUCTION a node, and 2) the ratio between the total resource power of nodes Traditional currencies have a centralized structure, and thus there run by the richest and the δ-th percentile participants is less than exist several problems such as a single point of failure and corrup- or equal to 1 + ε. Therefore, when m is sufficiently large, and ε and tion. For example, the global financial crisis in 2008 was aggravated δ are 0, ¹m; ε; δº-decentralization represents full decentralization, by the flawed policies of banks that eventually led to many bank which is an ideal state. -
Cryptonote Coin
CryptoNote Coin Michael Davis University of Miami April 2019 Proof of Work \scrypt" (used by Litecoin) has a uniform distribution of dependent lookups. Given a fast enough processor, it can be faster to only keep a small scratch-pad in memory and compute other dependencies on the fly. CryptoNight ensures that new blocks depend on all previous blocks, so CPU speed trades off with memory exponentially. Terminology I l = 2252 + 27742317777372353535851937790883648493 4 I A base point G = (x; − 5 ) I Hs a cryptographic hash function I Hp a deterministic hash function I Private keys are numbers a 2 [1; l − 1] I Public keys are points A = aG. I Private user keys are pairs (a; b) of private ec-keys I A standard address is a pair (A; B) derived from the private user key (a; b) Table of Contents Unlinkability Untraceability Alice ! Bob: Step 1 Alice reads Bob's public address (A; B). Alice ! Bob: Step 2 Alice generates r 2 [1; l − 1] and then computes P = Hs (rA)G + B. Alice ! Bob: Step 3 Alice generates the transaction. The transaction contains: I The transaction public key R = rG I The amount being transferred I The destination key P = Hs (rA)G + B Alice ! Bob: Step 4 Alice sends the transaction. Alice ! Bob: Step 5 Bob is listening on the stream of transactions. For each transaction, using R, the public key of the transaction, and a, one 0 of Bob's private ec-keys, Bob computes P = Hs (aR)G + B. If P0 = P (the destination key), then aR = arG = rA. -
Blockchain and The
NOTES ACKNOWLEDGMENTS INDEX Notes Introduction 1. The manifesto dates back to 1988. See Timothy May, “The Crypto Anarchist Manifesto” (1992), https:// www . activism . net / cypherpunk / crypto - anarchy . html. 2. Ibid. 3. Ibid. 4. Ibid. 5. Ibid. 6. Timothy May, “Crypto Anarchy and Virtual Communities” (1994), http:// groups . csail . mit . edu / mac / classes / 6 . 805 / articles / crypto / cypherpunks / may - virtual - comm . html. 7. Ibid. 8. For example, as we wi ll describe in more detail in Chapter 1, the Bitcoin blockchain is currently stored on over 6,000 computers in eighty- nine jurisdictions. See “Global Bitcoin Node Distribution,” Bitnodes, 21 . co, https:// bitnodes . 21 . co / . Another large blockchain- based network, Ethereum, has over 12,000 nodes, also scattered across the globe. See Ethernodes, https:// www . ethernodes . org / network / 1. 9. See note 8. 10. Some blockchains are not publicly accessible (for more on this, see Chapter 1). These blockchains are referred to as “private blockchains” and are not the focus of this book. 11. See Chapter 1. 12. The Eu ro pean Securities and Market Authority, “Discussion Paper: The Dis- tributed Ledger Technology Applied to Securities Markets,” ESMA / 2016 / 773, June 2, 2016: at 17, https:// www . esma . europa . eu / sites / default / files / library / 2016 - 773 _ dp _ dlt . pdf. 213 214 NOTES TO PAGES 5–13 13. The phenomena of order without law also has been described in other con- texts, most notably by Robert Ellickson in his seminal work Order without Law (Cambridge, MA: Harvard University Press, 1994). 14. Joel Reidenberg has used the term “lex informatica” to describe rules imple- mented by centralized operators online.