A Fistful of Bitcoins: Characterizing Payments Among Men ...

147 – Sarah Meiklejohn: Anonymity, Central Bank Cryptocurrencies And The Academic View On Bitcoin

147 – Sarah Meiklejohn: Anonymity, Central Bank Cryptocurrencies And The Academic View On Bitcoin submitted by MRDAT21 to Monero [link] [comments]

Post-Bitcoin Cryptocurrencies Symposium: Traceability in the Monero Blockchain

RIAT will be live tweeting today from the Symposium on Post-Bitcoin Cryptocurrencies in Vienna, Austria. The symposium is organised by the AIT (Austrian Institute of Technology) and features a lot of topics which are of interest to Monero, such as De-Anonymization in Bitcoin and Beyond (Sarah Meiklejohn) and Towards Better Privacy with Monero (Malte Moeser). Moeser co-wrote the paper An Empirical Analysis of Linkability in the Monero Blockchain and An Empirical Analysis of Traceability in the Monero Blockchain.

submitted by parasew to Monero [link] [comments]

Agreement with Satoshi – On the Formalization of Nakamoto Consensus

Cryptology ePrint Archive: Report 2018/400
Date: 2018-05-01
Author(s): Nicholas Stifter, Aljosha Judmayer, Philipp Schindler, Alexei Zamyatin, Edgar Weippl

Link to Paper


Abstract
The term Nakamoto consensus is generally used to refer to Bitcoin's novel consensus mechanism, by which agreement on its underlying transaction ledger is reached. It is argued that this agreement protocol represents the core innovation behind Bitcoin, because it promises to facilitate the decentralization of trusted third parties. Specifically, Nakamoto consensus seeks to enable mutually distrusting entities with weak pseudonymous identities to reach eventual agreement while the set of participants may change over time. When the Bitcoin white paper was published in late 2008, it lacked a formal analysis of the protocol and the guarantees it claimed to provide. It would take the scientific community several years before first steps towards such a formalization of the Bitcoin protocol and Nakamoto consensus were presented. However, since then the number of works addressing this topic has grown substantially, providing many new and valuable insights. Herein, we present a coherent picture of advancements towards the formalization of Nakamoto consensus, as well as a contextualization in respect to previous research on the agreement problem and fault tolerant distributed computing. Thereby, we outline how Bitcoin's consensus mechanism sets itself apart from previous approaches and where it can provide new impulses and directions to the scientific community. Understanding the core properties and characteristics of Nakamoto consensus is of key importance, not only for assessing the security and reliability of various blockchain systems that are based on the fundamentals of this scheme, but also for designing future systems that aim to fulfill comparable goals.

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Dandelion++: Lightweight Cryptocurrency Networking with Formal Anonymity Guarantees

arXiv:1805.11060
Date: 2018-05-28
Author(s): Giulia Fanti, Shaileshh Bojja Venkatakrishnan, Surya Bakshi, Bradley Denby, Shruti Bhargava, Andrew Miller, Pramod Viswanath

Link to Paper


Abstract
Recent work has demonstrated significant anonymity vulnerabilities in Bitcoin's networking stack. In particular, the current mechanism for broadcasting Bitcoin transactions allows third-party observers to link transactions to the IP addresses that originated them. This lays the groundwork for low-cost, large-scale deanonymization attacks. In this work, we present Dandelion++, a first-principles defense against large-scale deanonymization attacks with near-optimal information-theoretic guarantees. Dandelion++ builds upon a recent proposal called Dandelion that exhibited similar goals. However, in this paper, we highlight simplifying assumptions made in Dandelion, and show how they can lead to serious deanonymization attacks when violated. In contrast, Dandelion++ defends against stronger adversaries that are allowed to disobey protocol. Dandelion++ is lightweight, scalable, and completely interoperable with the existing Bitcoin network. We evaluate it through experiments on Bitcoin's mainnet (i.e., the live Bitcoin network) to demonstrate its interoperability and low broadcast latency overhead.

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A Bitcoin-Style Currency for Central Banks: The Bank of England asked researchers to invent a digital currency with a more centralized design.

This is an automatic summary, original reduced by 70%.
Now researchers have invented a Bitcoin-like system that could make digital cash more practical by allowing a central bank such as the Federal Reserve to control it.
The system, RSCoin, was designed by researchers Sarah Meiklejohn and George Danezis at University College London, at the suggestion of the U.K.'s central bank, the Bank of England.
RSCoin's ledger is solely in the hands of the central bank, which would also retain a special encryption key that could be used to control the money supply-for example, to take actions like the quantitative easing programs the Federal Reserve and other central banks put in place after the 2008 financial crisis.
A small collection of third-party organizations would be chosen by the central bank to process new transactions and submit them for inclusion in the central ledger.
Bhagwan Chowdhry, a professor of finance at UCLA, says that by adopting a system like RSCoin, central banks could enable the financial system to serve people much better.
One reason a central bank might like a digital currency is that its ledger provides a very detailed record of financial activity.
Summary Source | FAQ | Theory | Feedback | Top five keywords: Bank#1 digital#2 central#3 system#4 more#5
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O Preço do Bitcoin pode chegar a 98500 dólares segundo analistas de Wall Street

O preço do bitcoin pode subir para até $ 98.500, de acordo com analistas da empresa de serviços financeiros e de investimentos Wedbush Securities.
Um relatório dos analistas Gil Luria e Aron Turner, que tem sido referenciado em StreetInsider.com, tem uma visão extremamente positiva do bitcoin, sugerindo que a moeda digital tem o potencial de sacudir o espaço de pagamentos atual.
Intitulado Bitcoin: O Valor Intrínseco Como Um Canal Para Rede de Tecnologia Disruptiva De Pagamento, o relatório afirma:
"Entre outras facetas, acreditamos que o bitcoin e a tecnologia associada à ele representam uma potencial ruptura que mudará o jogo para as nossas empresas de pagamento."
Os autores argumentam ainda cryptomoeda oferece uma "alternativa poderosa para redes de marca", devido ao seu processamento descentralizado, novas funcionalidades e utilização de taxas baseadas no mercado.
O preço do bitcoin tem sido um Hot Topic desde a semana passada, com a moeda digital aumentando para os vertiginosos US$ 1165 no sábado, de acordo com theCoinDesk BPI. Em Mt. Gox, o preço superou US$ 1242, ultrapassando o preço do ouro pela primeira vez (o ouro estava em 1241 dólares por onça).
Erik Voorhees, que vendeu o site de apostas SatoshiDice por 126.315 BTC este ano, disse que isto mostrou em que "trunfo respeitável" o bitcoin está se tornando.
"Claramente, o Bitcoin não é mais só uma moeda insignificante. Ele está jogando na grande liga - valendo mais do que uma parte do Google ou da Apple, e até mesmo mais do que uma onça de ouro", disse ele na época.
O valor tem flutuado nestes últimos dias, com o preço, no momento da escrita deste artigo, pairando em torno de US$ 1071.
Sobe ou desce?
Muitas pessoas têm afirmado que o valor alto atual é meramente um aumento temporário e que em breve cairá para o mesmo nível observado em setembro e outubro (cerca de US $ 120 - $ 150), ou talvez ainda mais baixos.
Luria e Turner discordam, acreditando que o valor vai continuar a aumentar nos próximos anos. Eles disseram:
"Acreditamos que a subida dos preços do bitcoin ajudou a construir a rede, e assim, consolidando o seu valor, especialmente vis-à-vis outras moedas alternativas. Com base neste quadro, nós postulamos que os preços atuais refletem um auge de 1% do total da demanda potencial do Bitcoin em 10 anos".
No mês passado, os gêmeos Winklevoss comentaram que eles previam um aumento de 100 vezes no preço do Bitcoin. Na época de seus comentários, o preço do bitcoin foi de US $ 343 de modo que o valor já aumentou mais de 211%.
Falando à CNBC na conferência Dealbook em Nova York, Tyler Winklevoss, que estava envolvido na criação do Facebook, disse: "Algumas pessoas definitivamente o veem [bitcoin] como um Ouro 2.0".
Os Milhões de Clamath
Ex-executivo do Facebook, Chamath Palihapitiya, também é muito otimista a respeito do bitcoin.
No final de outubro, ele revelou que possuía US$ 5 milhões no valor da moeda digital, mas disse que estava esperando para alcançar cerca de 10-15 milhões de dólares com ela. Em 29 de outubro, o preço do bitcoin foi ligeiramente inferior a US $ 200, por isso é provável que ele tinha cerca de 25.000 BTC. Essa quantidade de bitcoins agora vale mais de US $ 26 milhões, por isso parece que Palihapitiya conseguiu o que desejava e um pouco mais.
Em maio, ele escreveu um artigo para a Bloomberg afirmando que o Bitcoin pode se tornar uma "versão melhorada" do ouro, ou mesmo um substituto para o metal precioso. Com todo o ouro do mundo totalizando aproximadamente US $ 8 trilhões, Palihapitiya disse que se o bitcoin substituisse o ouro como reserva de valor cada bitcoin custaria quase $ 400.000, uma vez que todos os 21 milhões de bitcoins fossem minados (US $ 8 trilhões/21milhões BTC).
"Se o Bitcoin se tornar algo maior - uma moeda de reserva útil, então cuidado: Seu valor será muito superior $ 400.000", escreveu ele, acrescentando:
"Eu pessoalmente acho que o Bitcoin já é superior ao ouro. O seu papel como moeda ainda está para ser determinado, mas ao longo da próxima década, ser o Ouro 2.0 será suficiente, considerando que isso representaria um retorno de mais de 3.000 vezes".
O problema com a volatilidade
Enquanto muitas pessoas acreditam que, a longo prazo, o preço do bitcoin será consideravelmente maior do que é agora, a visão comum é que a sua volatilidade continuará no curto prazo.
Luria e Turner explicaram em seu relatório que esta volatilidade é o resultado de um "processo de descoberta de preço estendida". Acredita-se quanto maiores forem os ganhos líquidos do bitcoin e quanto mais ele for amplamente aprovado, maior a probabilidade de se estabilizar o seu preço.
Atualmente, a volatilidade da moeda é o fator que está fazendo com que um alto percentual de pessoas leve o bitcoin a sério.
Na Universidade da Califórnia em San Diego, a pesquisadora Sarah Meiklejohn, que escreveu um artigo chamado Um Punhado DE Bitcoins: Caracterizando Pagamentos Entre Homens Sem Nome, disse ao CoinDesk que a coisa que a deixa "mais nervosa" a respeito do bitcoin é a sua volatilidade .
"É um problema do tipo galinha ou ovo. Você precisa de mais pessoas adotando o bitcoin a fim de estabilizar isso, mas as pessoas estão se afastando porque elas o veem como volátil e como um investimento de risco", disse ela.
A solução para este problema ainda não está claro, mas a comunidade bitcoin e os negócios dentro dele continuam a trabalhar arduamente para tornar mais fácil para os comerciantes aceitar bitcoins e para os consumidores obtê-los e em seguida gastá-los.
Qual você acha que é a chave para a estabilidade do bitcoin?
Traduzido por Sarah Alexandre Original em: http://www.coindesk.com/bitcoin-price-reach-98500-say-wall-street-analysts/
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ESTADÃO | Bitcoin prospera em meio a dúvidas

SÃO PAULO – A cotação da moeda virtual Bitcoin atingiu, na semana passada, o seu ponto mais alto no Mt.Gox – serviço de câmbio mais popular da rede – desde que começou a circular, em 2009. A moeda chegou ao valor de US$ 458. Há pouco mais de um mês, a cotação não passava dos US$ 150. A volatilidade impressiona, mas parece não assustar. A chamada “moeda da internet” não para de ganhar adeptos no mundo todo e preocupa bancos e governos que não participam do jogo.
O desafio para esse sistema monetário tão rebelde quanto a própria internet, agora que ganhou os holofotes, é se provar maduro e confiável, embora não faltem críticos dizendo que a moeda virtual é brincadeira de criança.
Em outubro, o professor de negócios do Massachusetts Institute of Technology (MIT), Simon Johnson, previu que o Bitcoin sofreria “grande retaliação política” e questionou se “as pessoas por trás da moeda” estariam prontas para isso. Na ocasião, o diretor de tecnologia do BitPay (que faz a intermediação de compra e venda de itens por meio do Bitcoin) contou estar sendo procurado por autoridades interessadas em saber das atividades da startup.
Desde a derrubada do Silk Road, site onde usuários protegidos pelo anonimato compravam drogas e armas usando bitcoins, o interesse dos Estados só tem aumentado. Prova disso, é a sessão marcada para hoje no Senado americano para discutir moedas virtuais.
Debate
O economista e professor da USP, Gilson Schwartz, vê nas moedas virtuais potencial para afetar a economia do “mundo real”. “É certo que exageros tornam-se autodestrutivos. A moeda sem Estado é um instrumento pré-capitalista, o Estado sem moeda existiria apenas numa distopia comunista com planejamento centralizado”, avalia. “Entre esses extremos, os meios de pagamento digitais ainda podem crescer muito e, sim, afetar o valor de moedas emitidas por governos.”
A moeda virtual, no entanto, é cercada de críticos, como o economista Paul Krugman, que classificou o Bitcoin como um “sonho impossível”, e questionou a integridade do seu sistema. Pesquisadores da Universidade de Cornell, nos EUA, apontaram recentemente uma “brecha” no sistema de gestão e emissão da moeda que permitiria a um grupo de pessoas ganhar mais do que mereciam e, assim, corromper o caráter descentralizado da rede.
A estudante de graduação Sarah Meiklejohn, da Universidade da Califórnia (UCLA), diz que é possível rastrear as transações da moeda caso seja necessário. Para isso, o governo ou as autoridades policiais precisariam ter controle das agências de câmbio virtuais, o que acabaria com a garantia da privacidade das operações.
Para Rodrigo Batista, CEO do Mercado Bitcoin, maior site de câmbio da moeda do Brasil, a aprovação do Estado – como fez a Alemanha, ao considerar o Bitcoin uma moeda aceitável – é fundamental para que o seu uso ganhe escala. Enquanto isso não acontece, ele continua a incentivar o uso de Bitcoin no Brasil. O primeiro a ser convencido foi o taxista paulistano Fernando Moreira. “Não tenho medo do novo. Por enquanto, me dei bem. O Rodrigo pagou a corrida com 0,4 centavos de Bitcoin. Na época, isso valia R$ 70, mas, com a cotação de hoje, já dá R$ 500”, comemora. “Ele foi meu único cliente, mas na Copa isso vai bombar”, prevê.
Embora os maiores envolvidos com a moeda no Brasil sejam especuladores, que lucram com o sobe e desce da cotação, a tendência é o uso do Bitcoin por serviços aumentar. A responsável pelo Bar Las Magrelas, Talita Noguchi, está confiante. “Pelo que vi desde que implementei, a coisa funciona. E o negócio vai ficar maior, você vai ver.”
ESTADÃO
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Blockchain Workshops - YouTube 147 – Sarah Meiklejohn: Anonymity, Central Bank Cryptocurrencies And The Academic View On Bitcoin Sarah Meiklejohn: Blockchains and Transparency TDC16 CACM Apr. 2016 - A Fistful of Bitcoins Panel: Technical Challenges: Blockchain Scalability and Others - Blockchain Workshops - Sydney 2015

Bitcoin is a purely online virtual currency, unbacked by either physical commodities or sovereign obligation; instead, it relies on a combination of cryptographic protection and a peer-to-peer protocol for witnessing settlements. Consequently, Bitcoin has the unintuitive property that while the ownership of money is implicitly anonymous, its flow is globally visible. In this paper we explore ... With academic research on Bitcoin and cryptocurrencies still in its infancy, Sarah Meiklejohn's track record of publications in the area stands out. The UCL computer science professor has explored topics ranging from anonymity in Bitcoin to how a central bank could go about issuing a cryptocurrency. Topics covered included: What techniques can be used to deanonymize Bitcoin users How Bitcoin's ... Sarah Meiklejohn Marjori Pomarole Grant Jordan Kirill Levchenko Damon McCoyy Geoffrey M. Voelker Stefan Savage University of California, San Diego George Mason University y ABSTRACT Bitcoin is a purely online virtual currency, unbacked by either phys- ical commodities or sovereign obligation; instead, it relies on a combination of cryptographic protection and a peer-to-peer proto-col for ... Sarah Meiklejohn About Me Bio I am a Professor in Cryptography and Security at UCL, in the Computer Science department. I am affiliated with the Information Security Group, and am also a member of the Open Music Initiative, a fellow of the Alan Turing Institute, and an Associate Director of the Initiative for Cryptocurrencies and Contracts (IC3). Sarah Meiklejohn In order to guarantee a fair and transparent voting process, electronic voting schemes must be verifiable. Most of the time, however, it is important that elections also be anonymous.

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Blockchain Workshops - YouTube

147 – Sarah Meiklejohn: Anonymity, Central Bank Cryptocurrencies And The Academic View On Bitcoin - Duration: 1:07:31. Epicenter Podcast 1,753 views. 1:07:31. Billy Graham's Last Message to ... Panelists: Sarah Meiklejohn (UCL), Gregory Meredith (Synereo), Peter Todd (Bitcoin Core Dev), Vlad Zamfir (Ethereum) Moderated by Constance Choi (Seven Advisory/CNRS) What are the current ... Sarah Meiklejohn discusses "A Fistful of Bitcoins" (cacm.acm.org/magazines/2016/4/200174), a Research Highlights article in the April 2016 Communications of the ACM. Panelists: Sarah Meiklejohn (UCL), Peter Todd (Bitcoin Core Developer), Dominic Williams (String), Vlad Zamfir (Ethereum) Moderated by Henning Diedrich (IBM) A brief introduction of the various ... With academic research on Bitcoin and cryptocurrencies still in its infancy, Sarah Meiklejohn's track record of publications in the area stands out. The UCL computer science professor has explored ...

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