Blockchain Papers

Noah Vardi

Il saggio propone alcune considerazioni sulla natura giuridica delle 'criptovalute' e dei Bitcoin in particolare, in assenza di specifica legislazione che ne definisca i caratteri e che individui la disciplina loro applicabile.

Kinga Kądziołka

Artykuł porusza problem identyfikacji (w oparciu o rozkład Benforda) nietypowych transakcji w sieci Bitcoin. Dla przykładowo wybranych adresów portfeli Bitcoin porównano rozkład Benforda z rozkładem częstotliwości występowania poszczególnych cyfr na pierwszej najbardziej znaczącej pozycji w kwotach transakcji związanych z tymi adresami. Rozkłady te nie były zgodne z rozkładem Benforda. Zwrócono uwagę na konieczność zachowania dużej ostrożności przy analizowaniu transakcji za pomocą narzędzi statystycznych takich jak rozkład Benforda. Brak zgodności z rozkładem Benforda w żadnym wypadku nie jest równoznaczny z prowadzeniem działalności niezgodnej z prawem. Z drugiej strony, zgodność z rozkładem Benforda nie stanowi gwarancji tego, że nie występują nieprawidłowości.

J.A. Bergstra

It is argued that a Bitcoin-style money-like informational commodity may constitute an effective instrument for the further development of Islamic Finance. The argument involves the following elements: (i) an application of circulation theory to Bitcoin with the objective to establish the implausibility of interest payment in connection with Bitcoin, (ii) viewing a Bitcoin-like system as a money-like exclusively informational commodity with the implication that such a system need not support debt, (iii) the idea that Islamic Finance imposes different requirements compared to conventional financial policies on a money concerning its use as a tool for achieving social and economic objectives, and (iv) identification of two aspects of mining, gambling and lack of trust, that may both be considered problematic from the perspective of compliance with the rules of Islamic Finance and a corresponding proposal to modify the architecture of mining in order to improve compliance with these rules.

Torbjørn Langland, Kristian Klomsten Skordal

Recent years have seen the emergence of a new class of currencies, called\ncryptocurrencies. These currencies use cryptography to provide security\nand peer-to-peer networking to provide a decentralized system. Bitcoin is\nthe most popular of these currencies. It uses a two-pass\nSHA-256 hash at its core. Producing new bitcoins is done through a process\nreferred to as "mining", which involves a brute-force search for a hash with\na specific value. This process requires large amounts of computing power.\n\nCurrent-generation hardware for bitcoin mining includes highly-optimized\nASIC chips which provide huge amounts of performance. However, designers of\nsuch chips are having problems with delivering enough power and cooling\nto the chips. To alleviate this problem, this thesis looks at the possibilities\nof using heterogeneous computing to reduce power consumption and produce a more\nenergy-efficient mining solution.\n\nA SHA-256 accelerator and a DMA module is developed and integrated into a tile for\nthe Single-ISA Heterogeneous MAny-core Computer, SHMAC, and a system with\nmultiple cores is used to exploit the thread-level parallelism provided by\nthe platform. The system is tested using a benchmark to find out what performance\nand energy efficiency can be expected when using the system for bitcoin mining.\n\nThe results show a maximum performance of 175,7 kH/s when running the benchmark\napplication on 14 cores using the SHA-256 accelerator and the DMA module. The best\nenergy efficiency was obtained when running on 14 cores without the DMA enabled,\nat 163,2 kH/J. The results does not compare well to specialized FPGA-based\nbitcoin miners, but demonstrates the SHMAC platform's large degree of thread-level parallelism\nwhich can be better exploited in other applications.

Francesca Musiani, Cécile Méadel, Alexandre Mallard

La construction de nouvelles formes de monnaie électronique est l’un des domaines d’application de la technologie pair-à-pair qui a conduit à des développements innovants au cours des dernières années. Bitcoin est certainement parmi les exemples les plus intéressants à cet égard. Basée sur un protocole P2P publié en 2009 par un mystérieux développeur ou groupe de développeurs (Nakamoto, 2009), à ce jour toujours non identifié, et rapidement adoptée par un nombre surprenant d’utilisateurs de l...

Ilias Giechaskiel

The Bitcoin cryptocurrency relies heavily on a variety of cryptographic functions and operations, which are currently assumed to be secure, but will inevitably be broken in the future. As Bitcoin tries to compete against traditional currencies, it remains to be seen how the Bitcoin protocol will need to change in response to weakened cryptography. To this end, this study systematically evaluates the effects of broken cryptographic primitives on the operation of the Bitcoin network, and the changes to the Bitcoin protocol that will be necessary in response. We conclude that a broken hash function only requires switching over to a new hash function, without the need to re-write the blockchain, and is well serviced by the “checkpoint” mechanisms already built into Bitcoin. However, a vulnerability of the signature scheme cannot be dealt with in the same manner without side-e.ects, as it may lead to lost or stolen coins, even if the process is gradual and is conducted before the cryptographic primitive is broken. We conclude that solving this problem either requires some degree of centralization, or the use of Zero-Knowledge Proofs along or on top of Bitcoin.

Imre Szücs, Attila Kiss

The role of Bitcoin -open source virtual peer-to-peer money -in finance has become more important with the increasing acceptance by service providers. Nevertheless several financial institutes and governments explain their revulsion against Bitcoin, due to the unknown financial risks behind it which could have an impact on the global financial world. In this paper we examine the relationship between BTC/USD exchange rate and the network properties of the underlying transactional graph. The main goal of our research is to get a deeper understanding on the behavior of Bitcoin and ground further researches on exploring the financial risk. To characterize the transactional graph network analysis techniques, while to examine the relationship data mining and time series analysis techniques were used.

James Gatto, Elsa S. Broeker

Bitcoin is a virtual currency transaction protocol.It also is a type of virtual currency.One of Bitcoin's unique features is that it is decentralized; it is not created or issued by a single person or entity.Rather, it is "mined" by miners that are issued bitcoins in exchange for solving complex math problems with special software.Bitcoins may be converted to governmentissued legal tender (commonly referred to as fiat currency) or other types of virtual currency through an exchange, or they may be used to purchase goods and services from any of the tens of thousands of merchants who accept bitcoins for payment.The Bitcoin protocol enables the transfer of bitcoins and also can be used for other purposes, such as providing the infrastructure for smart contracts, escrow systems, smart property/title systems, and much more.Many other virtual currencies exist.Some are centralized virtual currencies that are created and issued by a single entity.Some of these virtual currencies may be converted to fiat currency, but others may not.Many are "closed loop" virtual currencies that may only be used to obtain goods and services of the issuer.

Michele Ciampi, Giuseppe Persiano, Luisa Siniscalchi, Ivan Visconti

The Fiat-Shamir (FS) transform is a popular technique for obtaining practical zero-knowledge argument systems. The FS transform uses a hash function to generate, without any further over-head, non-interactive zero-knowledge (NIZK) argument systems from public-coin honest-verifier zero-knowledge (public-coin HVZK) proof systems. In the proof of zero knowledge, the hash function is modeled as a programmable random oracle (PRO). In TCC 2015, Lindell embarked on the challenging task of obtaining a similar transform with improved heuristic security. Lindell showed that, for several interesting and practical languages, there exists an efficient transform in the non-programmable random oracle (NPRO) model that also uses a common reference string (CRS). A major contribution of Lindell’s transform is that zero knowledge is proved without random oracles and this is an important step towards achieving efficient NIZK arguments in the CRS model without random oracles. In this work, we analyze the efficiency and generality of Lindell’s transform and notice a significant gap when compared with the FS transform. We then propose a new transform that aims at filling this gap. Indeed our transform is almost as efficient as the FS transform and can be applied to a broad class of public-coin HVZK proof systems. Our transform requires a CRS and an NPRO in the proof of soundness, similarly to Lindell’s transform. 1

Maria Letizia Perugini, Paolo Dal Checco

Please find the English version of this paper at http://ssrn.com/abstract=2729548 . Italian Abstract: Nel 2008 il protocollo Bitcoin ha introdotto una nuovo modo di trasferire diritti: il modello di Blockchain, uno schema matematico che combina una serie di algoritmi per procedere all'incorporazione di determinati diritti in una stringa digitale trasferibile. Una delle evoluzioni di quel protocollo è rappresentata dagli smart contract, un modello ancora da definire a nei dettagli tecnici e giuridici in cui alcune clausole del contratto vengono tradotte in codice informatico per l'esecuzione automatica in una blockchain derivata dal protocollo Bitcoin. Questo paper propone una prima valutazione dell'argomento basata sulla ricognizione dello stato dell'arte. English Abstract: In 2008 the Bitcoin protocol has introduced a new way to transfer rights: the blockchain model, a method combining mathematical algorithms in order to secure rights in transferrable digital string. One of the implementations of that system is represented by smart contracts, a model that is still to be defined in technical and legal details. The scheme turns specific contractual provisions in executable digital codes, designed for self execution in a Bitcoin derived blockchain system. This paper proposes a preliminary evaluation based on the state of the art.

Dmitri Kosten

No abstract is available for this record.

Essam Ghadafi

No abstract is available for this record.

Michael B. Abramowicz

No abstract is available for this record.

Jason Paul Cruz, Yuichi Kaji

The role-based access control (RBAC) is a natural and versatile model of the access control principle. In the real world, it is common that an organization provides a service to a user who owns a certain role that was issued by a different organization. However, such a trans-organizational RBAC is not common in a computer network because it is difficult to establish both the security that prohibits malicious impersonation of roles and the flexibility that allows small organizations/individual users to fully control their own roles. This study proposes a system that makes use of Bitcoin technology to realize a trans-organizational RBAC mechanism. Bitcoin, the first decentralized digital currency, is a payment network that has become a platform for innovative ideas. Bitcoin’s technology, including its protocol, cryptography, and open-source nature, has built a good reputation and has been applied in other applications, such as trusted timestamping. The proposed system uses Bitcoin technology as a versatile infrastructure to represent the trust and endorsement relationship that are essential in RBAC and to realize a challenge-response authentication protocol that verifies a user's ownership of roles.

Joshua Elkington

Bitcoin is a decentralized peer-to-peer payment system that has the potential to disrupt the financial industry. In order for the Bitcoin network to function properly, people within the network need to follow the protocol and contribute computing power. However, selfish strategies can be used to disproportionately increase one’s payoff relative to their computational power. Three approaches are used to analyze selfish mining strategies in the Bitcoin network in order to determine when this strategy will dominate.

Divya Rana, Syed Md Faisal Ali Khan, Arvind Arahant, Jitender Kumar Chaudhary

This study investigates the concept of green cryptocurrencies as a potential solution to mitigate the ecological footprint associated with traditional cryptocurrencies. It explores their viability as a sustainable alternative to traditional currencies. The rising popularity of cryptocurrencies has brought about concerns regarding their environmental impact, particularly due to the energy-intensive nature of mining and transactions.In conclusion, the importance of exploring sustainable alternatives to traditional cryptocurrencies emphasizes the potential of green cryptocurrencies to address environmental concerns.It discusses the growing awareness within the cryptocurrency community and the general public regarding the urgent need to address these issues. Green cryptocurrencies employ alternative consensus mechanisms, such as Proof-of-Stake (PoS) or energy-efficient algorithms, and utilize renewable energy sources for mining and transactions.

Ashley Pittman

This Issue Brief looks at the rapidly growing area of cryptocurrency donations to nonprofit organizations. Given the recent IRS guidance issued on taxation of Bitcoin, specifically its decision to treat cryptocurrencies as property, questions now arise as to how charitable contributions of the coins will be valued for tax deductions. Though Bitcoin resembles most other capital gain property, its volatility, general decline in value, anonymity, and potential for abuse require specific guidance on valuation and substantiation so as to handle its unique nature and prevent larger deductions for charitable contributions than those to which taxpayers are entitled.

Michael Abramowicz

This paper proposes a self-governing cryptocurrency, dubbed Autonocoin. Cryptocurrency owners play formal tacit coordination games by making investments recorded on the blockchain. Such investments represent bets about the focal point resolution of normative issues, such as whether a proposed change to Autonocoin should occur. The game produces a result that resolves the issue. With a typical cryptocurrency, the client software establishes conventions that ultimately lead to the identification of the authoritative blockchain. Autonocoin completes a circle by making transactions on the blockchain that in turn define those conventions and the expected software behavior. The distributed consensus mechanism embodied by formal tacit coordination games, meanwhile, can make other types of decisions, including which of competing blockchains is authoritative and whether new Autonocoins should be rewarded to benefit those who have taken actions to benefit Autonocoin. This establishes a unique funding model for a cryptocurrency, and it addresses objections to cryptocurrencies issued predominantly to the initial founders, as well as to those that encourage wasteful mining activities.

Wojciech Nowakowski

No abstract is available for this record.

Paul McCullum

Bitcoin, a virtual currency created in 2009 by an individual or group using the alias Satoshi Nakamoto, is based on a decentralized peer-to-peer system. Transactions are made with no intermediary. There are no banks involved, little to no transaction fees, and transactions are almost instantaneous. Transactions are verified by network nodes, and the network uses a public ledger called the block chain to record transactions. There is no central repository or administrator. Treasury categorizes it as a decentralized virtual currency. As public acceptance increases, so too does the number of merchants willing to accept bitcoin as a form of payment. But even though the public is slowly embracing bitcoin as a form of payment (thus giving it characteristics of a currency), public officials continue to struggle with the question of whether bitcoin is a currency — and therefore subject to appropriate currency regulations — or if it is simply property, making transactions in bitcoin more akin to barter.

Ittay Eyal

An open distributed system can be secured by requiring participants to present proof of work and rewarding them for participation. The Bitcoin digital currency introduced this mechanism, which is adopted by almost all contemporary digital currencies and related services. A natural process leads participants of such systems to form pools, where members aggregate their power and share the rewards. Experience with Bitcoin shows that the largest pools are often open, allowing anyone to join. It has long been known that a member can sabotage an open pool by seemingly joining it but never sharing its proofs of work. The pool shares its revenue with the attacker, and so each of its participants earns less. We define and analyze a game where pools use some of their participants to infiltrate other pools and perform such an attack. With any number of pools, no-pool-attacks is not a Nash equilibrium. We study the special cases where either two pools or any number of identical pools play the game and the rest of the participants are uninvolved. In both of these cases there exists an equilibrium that constitutes a “tragedy of the commons” where the participating pools attack one another and earn less than they would have if none had attacked. For two pools, the decision whether or not to attack is the miner’s dilemma, an instance of the iterative prisoner’s dilemma. The game is played daily by the active Bitcoin pools, which apparently choose not to attack. If this balance breaks, the revenue of open pools might diminish, making them unattractive to participants.

Benjamin Beckdominik

No abstract is available for this record.

Kristian Đokić, Mirjana Radman Funarić, Katarina Potnik Galić

No abstract is available for this record.

Ren Zhang

Bitcoin [1] is a decentralized crytocurrency system launched by a mysterious creator Satoshi Nakamoto. Its novel and open design attracts not only a lot of users but also much attention from academia. The core of Bitcoin’s