De nombreuses monnaies parallèles circulent depuis toujours à côté de la monnaie officielle. Aujourd’hui, une nouvelle génération de monnaie est en train de naître des nouvelles technologies : les crypto-monnaies, dont l’exemple le plus connu est le bitcoin. Ces monnaies n’existent que sous forme de code informatique, sans équivalent papier ou métallique. Bien qu’elles constituent une avancée technologique remarquable, elles soulèvent de nombreux défis tant éthiques qu’économiques, que ce numéro de Regards économiques essaie d’éclairer
Nicolas T. Courtois, Guangyan Song, Ryan Castellucci
Abstract In this paper, we study and give the first detailed benchmarks on existing implementations of the secp256k1 elliptic curve used by at least hundreds of thousands of users in Bitcoin and other cryptocurrencies. Our implementation improves the state of the art by a factor of 2.5 with a focus on the cases, where side channel attacks are not a concern and a large quantity of RAM is available. As a result, we are able to scan the Bitcoin blockchain for weak keys faster than any previous implementation. We also give some examples of passwords which we have cracked, showing that brain wallets are not secure in practice even for quite complex passwords.
In recent years the distributed ledger technology (‘DLT’) has been presented as potentially disruptive for financial market applications. Since no reference implementation of such technology has emerged yet, it is not even clear how different it would be from the blockchain technology underlying bitcoin. Blockchain is a sub-optimal data structure if not associated to a virtual currency, i.e. to a native digital asset used to provide the economic incentive to reach distributed consensus on a transaction history. Since the interest for virtual currencies in the financial markets has remained marginal so far, most of the interest for DLT seems to boil down to the cryptographic enhancements of coupling secure messaging with shared databases. Such an evolutionary approach might be relevant, but hardly disruptive; instead, it is the availability for the first time ever in digital realm of a scarce asset, transferable but not replicable, to be groundbreaking. Bitcoin could prove to be digital gold as relevant as physical gold has been in the human history and the development of finance: it has already realized a permissionless transaction network and could play a crucial role in the history of money.
Bitcoin, a fascinating phenomenon of crypto-technology, has emerged in financial markets as a potential alternative to standard fiat currencies. It represents unique sociotechnical \necosystem working outside of any traditional markets, and its economy is still not well understood. Dynamics of Bitcoin price proves to be quite a controversial subject, but there is a strong indication that social factors mainly influence its economy. \n \nTechnical flaws and lack of any central authority issuing and controlling this digital currency make it vulnerable to abuse. It has been associated with controversy due to frequent incidents, namely hacks, theft, scam, and illicit use, which affected its ecosystem ever since it gained popularity. \n \nThis thesis adds to the discussion about social aspects of Bitcoin economy by analysing the changes in its price volatility in the context of incidents occurring in its \necosystem. As empirically proven, those negative events have no impact on the fluctuations of Bitcoin price.
Den Zentralbanken muss vertraut werden, die Währung nicht abzuwerten. Aber die Geschichte des Fiat‐Geldes ist in dieser Hinsicht voller Vertrauensbrüche (Satoshi Nakamoto am 11. Februar 2009 in einem Forum). Durch die immanente Offenheit des Open‐Source‐Bitcoin‐Systems werden die oben beschriebenen Limitationen des Transaktionssystems in der Bitcoin‐Szene heftig diskutiert, wobei diese Limitationen von den einen als Einschränkungen empfunden, von den anderen aber als Stärken des Systems gesehen werden. Ebenso wie die Limitationen des Systems werden die individuellen Lösungsansätze von Beginn an transparent diskutiert und analysiert.
Like how VoIP (Voice over Internet Protocol) disrupted cross‐border telephony, Bitcoin will bring huge savings and improved service in cross‐border payments and will therefore create the MoIP (Money over Internet Protocol) (Pantera Capital). Anhand einiger typischer Gradmesser der Netzwerkökonomie soll in der Folge aufgezeigt werden, welche massive Entwicklung das von Satoshi Nakamoto vorgeschlagene neue kryptografische Transaktionssystem innerhalb einer Zeitspanne von gut sechs Jahren genommen hat.
…the more it is adopted by a mass of users, the more it is secured (Counterparty). Inwieweit, ob und welche Kryptowährung schlussendlich langfristig weltweit akzeptiert wird, ist Thema zahlreicher und vielfältiger Diskussionen. Innerhalb der verschiedenen Kryptowährungen hat das Bitcoin‐System eindeutig einen massiven Vorsprung. Vorstellbar ist jedoch auch analog des Konzepts des freien Wettbewerbs unter den Währungen vom österreichischen Ökonomen Friedrich August von Hayek ein Nebeneinander verschiedenster Kryptowährungen. Jeder dieser Kryptowährungen könnte ein Wert durch eine Gruppe von Menschen, die sich dafür entscheiden, dieser Währung zu vertrauen, beigemessen werden. Diese Gruppe kann durch gemeinsame demografische, geografische oder ethische Interessen definiert werden. Damit Kryptowährungen jedoch von der breiten Öffentlichkeit genutzt werden, bedarf es noch Vor allem aber braucht es Akzeptanz und Nutzung der Kryptowährungen in der breiten Öffentlichkeit und hier liefert die Gratis‐Bitcoin‐Ökosphäre, bestehend aus Hunderten Faucet‐Webseiten, einen großen Beitrag.
Bitcoin offers a sweeping vista of opportunity to reimagine how the financial system can and should work in the Internet era (Marc Andreessen, General Partner at Andreessen Horowitz). Die Vorteile der Nutzung des Bitcoin‐Transaktionssystems als Ersatz für die momentan genutzten elektronischen Zahlungsverkehrssysteme sind offensichtlich, und doch gibt es immer noch viel Diskussion über Sinnhaftigkeit und Nutzbarkeit des Systems. Die Gründe dafür sind vielfältig und sollen das Thema der nächsten Ausführungen sein. Bei der Diskussion der Limitationen des Bitcoin‐Systems ist die relative Neuheit des Systems zu berücksichtigen, sodass es sich bei vielen der im Folgenden im Detail diskutierten Limitationen handelt es sich um Anfangsschwierigkeiten, an deren Lösung intensiv gearbeitet wird.
Darüber hinaus hat Bitcoin jedoch noch zusätzliche Vorteile: So wie im 19. Jahrhundert der Goldstandard eine Welle der Globalisierung losgelöst hat, kann der Bitcoin die Globalisierung von Handel und Dienstleistung auf eine neue Stufe heben. Der Bitcoin macht das Internet zur Währungsunion (Bitcoinblog.de). Die Bitcoin‐Architektur ermöglicht Dieses neue elektronische und weltweit verfügbare Zahlungssystem Die Bitcoin‐Technologie verteilt die Transaktionsverantwortlichkeiten über ein dezentrales Computernetzwerk, wodurch die Notwendigkeit der Involvierung teurer Finanzinstitute und Zahlungsdienstleister zur Authentifizierung und Überprüfung wegfällt und damit die Transaktionskosten und die Transaktionsdauer vermindert werden können.
Talent hits a target others cannot hit, Genius hits a target others cannot see (Arthur Schopenhauer). Bereits 2013 begannen sich neue Kryptowährungsunternehmen zu formieren, die sich von der Wild‐West‐Mentalität der Mt. Gox und der Silk Road abgrenzen wollten. Die entstehenden Kryptowährungsdienstleister – großteils finanziert von US Venture Capital-Gebern – unterwerfen sich teils freiwillig den Know Your Customer (KYC) Bestimmungen der Finanzaufsichtsbehören. Gleichzeitig entstanden Kryptowährungsstartups, deren Gründer die Meinung vertraten, dass eine Kooperation mit den Finanzinstituten bzw. den Fiatwährungen statt Konfrontation wirtschaftlich sinnvoller wäre und damit begannen, neue Kryptotransaktionssysteme mit dieser Zielrichtung zu entwickeln (beispielsweise Ripple Lab vgl. auch Abschn. 14.2.). Zeitgleich – auch hier spielten die Interessen der investierten Venture-Capital-Geber eine wichtige Rolle – begannen Startups intensiv am Einsatz des Bitcoin‐Transaktionssystems für alternative Zwecke zu arbeiten. Dabei wird unterschieden in:
Banks, as they exist now, are obsolete and will not exist as we know them in 10 years. Period. Without a doubt. We’ve seen this movie before. Is anyone using Delphi? CompuServe? AOL? What did they have in common? They tried to retrofit the Internet’s HTTP technology into their systems. They tried to force everyone into their closed loopholes. It worked, temporarily. You had a jump in revenues and profit, and then everybody found out you can deal directly with the source. You don’t need them They’re gone. The banking system is trying to do the same thing (Reggie Middleton, CEO of Veritaseum, designing P2P Smart Contracts through blockchain tech & inventor of UltraCoin). Wie schon oft in diesem Buch aufgezeigt, nutzt die Finanzwirtschaft schon jahrzehntelang Softwaresysteme wie das SWIFT-System, hat es aber bis dato geschafft, sich von der Digitalisierung des Internets abzugrenzen.
Die Möglichkeit der Programmierbarkeit des Bitcoins ist fast ein nachträglicher Einfall, auch wenn Sidechain‐Vorschläge diese Programmierbarkeit ein wenig leichter machen wollen und es bereits Altcoins mit verschiedenen spezifischen Anwendungen gibt. Im Gegensatz dazu wurde das Kryptowährungstechnologieprojekt Ethereum von Vitalik Buterin, seinem Erfinder, von Tag 1 als Software‐Entwicklungsplattform für dezentrale Applikationen konzipiert, und ihre Blockchain wurde speziell entwickelt, um die Ausführung dieser dezentralen Apps (auch Dapps genannt) zu unterstützen. Vitalik Buterin, 1994 in Russland geboren, war vor der Gründung von Ethereum auch involviert in die Entwicklungsprojekte Colored Coins und Mastercoins. Er gewann 2014 den "World Technology Award" und ein Stipendium des Risikokapitalgebers Peter Thiel. In dem Diskussionspapier zu Ethereum skizzierte Buterin vor allem die Grenzen einer Programmierbarkeit der Bitcoin‐Blockchain und schlug die Erstellung einer neuen komplett programmierbaren Blockchain mit einer turing‐vollständigen Programmiersprache vor. Anders als andere Blockchain‐Projekte soll die Ethereum Software nicht nur für einen Zweck nutzbar sein – sondern soll die Basis für die Erarbeitung aller möglichen Arten von Lösungen sein und dabei die Umsetzung intelligenter Verträge (Smart Contracts) ebenso erfassen als auch die Ethereum‐spezifische Idee von dezentralen autonomen Organisationen (DAOs).
There has recently been a flood of interest in potential new applications of blockchains, as well as proposals for more generic designs called public ledgers. Most of the novel proposals have been in the financial sector. However, the public ledger is an abstraction that solves several of the fundamental problems in the design of secure distributed systems: global time in the form of a strict linear order of past events, globally consistent and immutable view of the history, and enforcement of some application-specific safety properties. This paper investigates the applications of public ledgers to access control and, more specifically, to group management in distributed systems where entities are represented by their public keys and authorization is encoded into signed certificates. It is particularly difficult to handle negative information, such as revocation of certificates or group membership, in the distributed setting. The linear order of events and global consistency simplify these problems, but the enforcement of internal constraints in the ledger implementation often presents problems. We show that different types of revocation require slightly different properties from the ledger. We compare the requirements with Bitcoin, the best known blockchain, and describe an efficient ledger design for membership revocation that combines ideas from blockchains and from web-PKI monitoring. While we use certificate-based group-membership management as the case study, the same ideas can be applied more widely to rights revocation in distributed systems.
There has recently been a flood of interest in potential new applications of\nblockchains, as well as proposals for more generic designs called public\nledgers. Most of the novel proposals have been in the financial sector.\nHowever, the public ledger is an abstraction that solves several of the\nfundamental problems in the design of secure distributed systems: global time\nin the form of a strict linear order of past events, globally consistent and\nimmutable view of the history, and enforcement of some application-specific\nsafety properties. This paper investigates the applications of public ledgers\nto access control and, more specifically, to group management in distributed\nsystems where entities are represented by their public keys and authorization\nis encoded into signed certificates. It is particularly difficult to handle\nnegative information, such as revocation of certificates or group membership,\nin the distributed setting. The linear order of events and global consistency\nsimplify these problems, but the enforcement of internal constraints in the\nledger implementation often presents problems. We show that different types of\nrevocation require slightly different properties from the ledger. We compare\nthe requirements with Bitcoin, the best known blockchain, and describe an\nefficient ledger design for membership revocation that combines ideas from\nblockchains and from web-PKI monitoring. While we use certificate-based\ngroup-membership management as the case study, the same ideas can be applied\nmore widely to rights revocation in distributed systems.\n
Appearance of Bitcoin raise up evolution in currency. Blockchain database also raise up possibilities to share important data between untrusted peers. In this paper, we propose Arachneum, a decentralized, distributed, and model-view-controller-based web service using blockchain and new privileges model. Therefore, we can enjoy the freedom against censorship of government or organizations, keep transparency of our web services, fork our web services, and create/read/update/delete(CRUD) all model-view-controller(MVC) components dynamically.
The Internet of Things IoT is experiencing exponential growth in research and industry, but it still suffers from privacy and security vulnerabilities. Conventional security and privacy approaches tend to be inapplicable for IoT, mainly due to its decentralized topology and the resource-constraints of the majority of its devices. BlockChain BC that underpin the crypto-currency Bitcoin have been recently used to provide security and privacy in peer-to-peer networks with similar topologies to IoT. However, BCs are computationally expensive and involve high bandwidth overhead and delays, which are not suitable for IoT devices. This position paper proposes a new secure, private, and lightweight architecture for IoT, based on BC technology that eliminates the overhead of BC while maintaining most of its security and privacy benefits. The described method is investigated on a smart home application as a representative case study for broader IoT applications. The proposed architecture is hierarchical, and consists of smart homes, an overlay network and cloud storages coordinating data transactions with BC to provide privacy and security. Our design uses different types of BCs depending on where in the network hierarchy a transaction occurs, and uses distributed trust methods to ensure a decentralized topology. Qualitative evaluation of the architecture under common threat models highlights its effectiveness in providing security and privacy for IoT applications.
Swarms of robots will revolutionize many industrial applications, from targeted material delivery to precision farming. However, several of the heterogeneous characteristics that make them ideal for certain future applications --- robot autonomy, decentralized control, collective emergent behavior, etc. --- hinder the evolution of the technology from academic institutions to real-world problems. Blockchain, an emerging technology originated in the Bitcoin field, demonstrates that by combining peer-to-peer networks with cryptographic algorithms a group of agents can reach an agreement on a particular state of affairs and record that agreement without the need for a controlling authority. The combination of blockchain with other distributed systems, such as robotic swarm systems, can provide the necessary capabilities to make robotic swarm operations more secure, autonomous, flexible and even profitable. This work explains how blockchain technology can provide innovative solutions to four emergent issues in the swarm robotics research field. New security, decision making, behavior differentiation and business models for swarm robotic systems are described by providing case scenarios and examples. Finally, limitations and possible future problems that arise from the combination of these two technologies are described.
Pedro Moreno-Sánchez, Muhammad Bilal Zafar, Aniket Kate
Abstract The decentralized I owe you (IOU) transaction network Ripple is gaining prominence as a fast, low-cost and efficient method for performing same and cross-currency payments. Ripple keeps track of IOU credit its users have granted to their business partners or friends, and settles transactions between two connected Ripple wallets by appropriately changing credit values on the connecting paths. Similar to cryptocurrencies such as Bitcoin, while the ownership of the wallets is implicitly pseudonymous in Ripple, IOU credit links and transaction flows between wallets are publicly available in an online ledger. In this paper, we present the first thorough study that analyzes this globally visible log and characterizes the privacy issues with the current Ripple network. In particular, we define two novel heuristics and perform heuristic clustering to group wallets based on observations on the Ripple network graph. We then propose reidentification mechanisms to deanonymize the operators of those clusters and show how to reconstruct the financial activities of deanonymized Ripple wallets. Our analysis motivates the need for better privacy-preserving payment mechanisms for Ripple and characterizes the privacy challenges faced by the emerging credit networks.
Aggelos Kiayias, Ηλίας Κουτσουπιάς, Maria Kyropoulou, Yiannis Tselekounis
We study the strategic considerations of miners participating in the bitcoin's protocol. We formulate and study the stochastic game that underlies these strategic considerations. The miners collectively build a tree of blocks, and they are paid when they create a node (mine a block) which will end up in the path of the tree that is adopted by all. Since the miners can hide newly mined nodes, they play a game with incomplete information. Here we consider two simplified forms of this game in which the miners have complete information. In the simplest game the miners release every mined block immediately, but are strategic on which blocks to mine. In the second more complicated game, when a block is mined it is announced immediately, but it may not be released so that other miners cannot continue mining from it. A miner not only decides which blocks to mine, but also when to release blocks to other miners. In both games, we show that when the computational power of each miner is relatively small, their best response matches the expected behavior of the bitcoin designer. However, when the computational power of a miner is large, he deviates from the expected behavior, and other Nash equilibria arise.
Dimitris Chatzopoulos, Sujit Gujar, Boi Faltings, Pan Hui
The popularity of digital currencies, especially cryptocurrencies, has been continuously growing since the appearance of Bitcoin. Bitcoin is a peer-to-peer (P2P) cryptocurrency protocol enabling transactions between individuals without the need of a trusted authority. Its network is formed from resources contributed by individuals known as miners. Users of Bitcoin currency create transactions that are stored in a specialised data structure called a block chain. Bitcoin's security lies in a proof-of-work scheme, which requires high computational resources at the miners. These miners have to be synchronised with any update in the network, which produces high data traffic rates. Despite advances in mobile technology, no cryptocurrencies have been proposed for mobile devices. This is largely due to the lower processing capabilities of mobile devices when compared with conventional computers and the poorer Internet connectivity to that of the wired networking. In this work, we propose LocalCoin, an alternative cryptocurrency that requires minimal computational resources, produces low data traffic and works with off-the-shelf mobile devices. LocalCoin replaces the computational hardness that is at the root of Bitcoin's security with the social hardness of ensuring that all witnesses to a transaction are colluders. It is based on opportunistic networking rather than relying on infrastructure and incorporates characteristics of mobile networks such as users' locations and their coverage radius in order to employ an alternative proof-of-work scheme. Localcoin features (i) a lightweight proof-of-work scheme and (ii) a distributed block chain.
Saulo Ricci, Alex Borges, Helder Luiz, Daniel Sadoc Menasché · 5 authors
Apesar do crescente interesse em cripto moedas, tanto indústria quanto a academia sentem falta de análises quantitativas desses sistemas. Neste trabalho, caracterizamos o Bitcoin, um dos mais populares sistemas de cripto moedas, sob a ótica quantitativa. Visamos métricas importantes relacionadas a transações, como a probabilidade uma transação ser confirmada e o tempo decorrido para essa confirmação. Nossos resultados mostram que há um número não negligenciável de transações que não são confirmadas 24 horas após serem postadas na rede. Nesse caso, nós observamos uma alta correlação entre a taxa de uma transação, seu volume e a suspeita de que a transação não será confirmada. O trabalho mostra que transações do Bitcoin geralmente são confirmadas em períodos curtos, mas ainda assim, muito acima de tempos usuais de sistemas de cartão de crédito. Finalmente, nós provemos uma análise de nível de atividade simples, comparando um período importante na existência do sistema do Bitcoin –o fechamento do Silk Road– e um peróodo subsequente. Em resumo, concluimos que a rede Bitcoin se apresenta resiliente e não é dependente de hubs altamente centralizados.
Shayan Eskandari, Jeremy Clark, Abdelwahab Hamou-Lhadj
In this paper we discuss existing approaches for Bitcoin payments, as suitable for a small business for small-value transactions. We develop an evaluation framework utilizing security, usability, deployability criteria,, examine several existing systems, tools. Following a requirements engineering approach, we designed, implemented a new Point of Sale (PoS) system that satisfies an optimal set of criteria within our evaluation framework. Our open source system, Aunja PoS, has been deployed in a real world cafe since October 2014.
Till Neudecker, Philipp Andelfinger, Hannes Hartenstein
Flooding Peer-to-Peer (P2P) networks form the basis of services such as the electronic currency system Bitcoin. The decentralized architecture enables robustness against failure. However, knowledge of the network's topology can allow adversaries to attack specific peers in order to, e.g., isolate certain peers or even partition the network. Knowledge of the topology might be gained by observing the flooding process, which is inherently possible in such networks,, performing a timing analysis on the observations. In this paper we present a timing analysis method that targets flooding P2P networks, show its theoretical, practical feasibility. A validation in the real-world Bitcoin network proves the possibility of inferring network links of actively participating peers with substantial precision, recall (both ~ 40%), potentially enabling attacks on the network. Additionally, we analyze the countermeasure of trickling, quantify the tradeoff between the effectiveness of the countermeasure, the expected performance penalty. The analysis shows that inappropriate parametrization can actually facilitate inference attacks.
José Gladistone da Rocha, Carlo Kleber da Silva Rodrigues
O protocolo Bitcoin foi proposto há cerca de seis anos e sua adoção para a implementação de um sistema de transações financeiras tem se mostrado crescente em diferentes países no mundo. No entanto, há poucas obras na literatura voltadas ao esclarecimento de todas as etapas que envolvem o processo de negócio desse sistema. Neste contexto, este artigo tem o objetivo de apresentar a modelagem deste processo de negócio bem como detalhar como ocorre o seu processo primário Gerenciar Pagamento. Para tanto, são empregadas técnicas de Engenharia de Software e de Business Process Model and Notation. Os modelos desenvolvidos permitem mapear problemas críticos do sistema, explicitando em quais etapas do processo de negócio eles incidem. Isso viabiliza principalmente a proposição mais efetiva de soluções e otimizações com vistas à maior robustez global do sistema.