An Analysis of Anonymity in the Bitcoin System

Dandelion++: Lightweight Cryptocurrency Networking with Formal Anonymity Guarantees

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

Link to Paper

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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submitted by dj-gutz to myrXiv [link] [comments]

Why do I believe it was BCN destiny to be born in 2012?

Why do I believe it was BCN destiny to be born in 2012? Just look at this and see yourself:
1983 - Blind signatures were invented by David Chaum link 1997 - HashCash (proof of work system) was invented by Adam Back link
2001 - Ring signatures were invented by Ron Rivest, Adi Shamir, and Yael Tauman link
2003 - Mart n Abadi, Michael Burrows, and Ted Wobber presented "Moderately hard, memory-bound functions"link
2004 - Patrick P. Tsang and Victor K. Wei presented their paper "Short linkable ring signatures for e-voting, e-cash and attestation" link
2005 - Matthew Franklin and Haibin Zhang with "Unique Group Signatures" study link
2005 - Exponential memory-bound functions for proof of work protocols by Fabien Coelho link +2006 - "Traceable Ring Signature" by Fujisaki and Suzuki link
2008 - Bitcoin whitepaper by Satoshi Nakamoto link
2009 - Stronger key derivation via sequential memory-hard functions by Colin Percival link
2009 - First Bitcoin block was generated
2010 -2012 - Bitcoin Anonymity Problem Discussions link
2011 - An Analysis of Anonymity in the Bitcoin System, Fergal Reid and Martin Harrigwere link
5/15/2012 - Dorit Ron and Adi Shamir made Quantitative Analysis of the Full Bitcoin Transaction Graph link
6/8/2012 - Bytecoin Wiki started link
6/30/2012 - Bytecoin launch announcement link- first news
7/4/2012 - First BCN block was generated link
8/6/2012 - Destination Address Anonymization in Bitcoin (one-time addresses in BCN) link
10/19/2012 - Evaluating User Privacy in Bitcoin by Elli Androulaki, Ghassan O. Karame, Marc Roeschlin, Tobias Scherer, Srdjan Capkun. link
12/12/2012 -CryptoNote whitepaper v 1.0 link
12/13/2012 - Analysis of hashrate-based double-spending, Meni Rosenfeld link
10/17/2013 - CryptoNote whitepaper v 2.0 link
Here we see how the technology logically came to the advent of cryptocurrencies with ring signature and memory-bound function PoW implementation. Soon after Bitcoin's release the community started to raise concerns about its anonymity with multiple solutions and propositions. High concentration of theoretical papers on these topics in 2009-2011 most probably spurred the brightest minds to make attempts of practical e-cash with ring signatures realization. Therefore, BCN couldn't but appear in 2012.
Based on
submitted by joethejudge77 to BytecoinBCN [link] [comments]

Bitcoin: instável, o ‘ouro da internet’ ainda causa incerteza

RIO - “Vende-se uma BMW por 1,5 mil bitcoins”. Anúncios como esse, publicado no início de abril no Facebook, podem se tornar cada vez mais comuns, caso o ambicioso projeto da moeda virtual e descentralizada criada em 2009 se afirme no mercado. Mas nos últimos dias, o bitcoin deu sinais de como sua instabilidade pode atrapalhar os ideais de quem vê o “ouro da internet” como alternativa ao dinheiro fiduciário. Sem regulação central, a moeda supervalorizou até a marca dos US$ 266, perdeu metade do valor no dia seguinte, e retomou o curso positivo na semana seguinte. A montanha russa preocupa entusiastas, mas anima investidores de olho na onda especulativa.
Muitos especialistas apontam a crise de Chipre como um dos fatores mais importantes para a escalada do valor do bitcoin, que ganhou aspectos de bolha. Em tese, o temor de um congelamento de saques na Europa fez com que mais pessoas considerassem adquirir moedas virtuais. A cobertura na mídia também atraiu a atenção de investidores e contribuiu para a valorização.
A intensa flutuação atrapalha os planos de quem projetou o bitcoin para ser uma forma efetiva de pagamento. Amir Taaki, desenvolvedor britânico fortemente envolvido com o projeto, afirma que a integração do bitcoin à economia real já começou a acontecer em diversas partes da Europa, inclusive em Londres, mas a instabilidade é preocupante.
— A taxa de câmbio importa, porque quando o preço é volátil, é mais difícil oferecer serviços em bitcoin. Mas se o preço dobrar ou cair à metade não me preocupa muito. O que importa é um preço estável — diz o programador.
Outro efeito colateral dos holofotes sobre o bitcoin é a atração de ladrões virtuais. Como não há contas bancárias para armazenar o dinheiro eletrônico, as moedas são guardadas no próprio computador do usuário, facilitando ataques de hackers mal intencionados. Além disso, os sistemas de compra e venda ainda são vulneráveis aos chamados ataques de negação de serviço, orquestrados com o objetivo de desequilibrar o sistema.
No dia 11 de abril, um dia após a moeda virtual alcançar a marca de US$ 266, o site de negociações japonês MtGox, que concentra 80% das operações em todo o mundo, saiu do ar e informou que sofreu um ataque “mais forte do que o normal". No dia 18, o site voltou a sofrer quedas. Supostamente, os ataques seriam uma forma de forçar a chamada “panic sale”, que costumam derrubar os preços. — Provavelmente, o sistema ficará mais forte, conforme tiver mais poder computacional, análise e revisão. Mas o aumento do valor do bitcoin tem aumentado o interesse de grupos maliciosos. Eu esperaria um aumento da sofisticação dos ataques — analisa Fergal Reid, especialista em segurança da Universidade College Dublin, na Irlanda, que pesquisa o assunto desde 2011.
Mercado brasileiro é pequeno
Ainda não se sabe se a bolha da moeda realmente estourou e se a moeda caminha para a estabilidade. Para Mikko Hypponen, especialista de segurança da empresa finlandesa F-Secure e investidor em bitcoin, nada é previsível.
— Não ficaria surpreso de ver o bitcoin chegar aos US$ 1 mil — aposta.
No Brasil, poucos investidores viveram a emoção do aumento da bolha. A já rarefeita comunidade nacional está há meses órfã do maior site de negociações, o Mercado Bitcoin, alvo de invasões hackers no ano passado. De acordo com Leandro César, fundador do portal, a previsão é de que o site volte a funcionar na próxima semana. O serviço conta com cerca de 2 mil clientes. O bancário Rodrigo Batista, de 32 anos, continuou investindo em dólar durante o crescimento da bolha, mas resistiu à tentação de vender seus cerca de 100 bitcoins na alta. Segundo ele, é preciso ter cautela e compreender a novidade.
—Entrar no mercado pensando em ganho imediato é besteira, porque o bitcoin é imprevisível no curto prazo. Depende muito do comportamento das bolsas e da atuação dos hackers. Pensando nele como uma tecnologia nova, aí ele tem seu valor — conta Rodrigo, que acabou se tornando sócio do Mercado Bitcoin na última sexta-feira.
O futuro do bitcoin ainda é incerto. A engrenagem matemática por trás do projeto prevê o controle do valor da moeda por meio de alguns artifícios, como a emissão limitada. Atualmente há cerca de 11 milhões de bitcoins em circulação no mundo e a quantidade máxima é de 21 milhões, uma forma de evitar inflação. Mas o fator humano ainda é essencial para fazer com que o projeto funcione. Para Mikko Hypponen, da F-Secure, a moeda precisa lidar com muitas falhas.
— Qualquer moeda concorrente poderia tomar seu valor. Acho até provável, no longo prazo. O bitcoin tem vários problemas técnicos, alguns que foram resolvidos em outras moedas digitais De qualquer forma, acredito que alguma moeda digital vá se tornar algo comum ao longo da próxima década — prevê.
Já Amir Taaki acredita no amadurecimento da moeda e reconhece a necessidade de mais infraestrutura.
— Precisamos que serviços do dia a dia, como comida, viagens e habitação possam ser comprados com bitcoin. Precisamos criar uma economia completa com tudo que as pessoas precisam e esperam — defende Taaki
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View Fergal Reid (PhD)’s profile on LinkedIn, the world's largest professional community. Fergal has 15 jobs listed on their profile. See the complete profile on LinkedIn and discover Fergal’s connections and jobs at similar companies. Fergal Reid; Martin Harrigan; Anonymity in Bitcoin, a peer-to-peer electronic currency system, is a complicated issue. Within the system, users are identified by public-keys only. An attacker ... [email protected] Martin Harrigan Clique Research Cluster University College Dublin, Ireland [email protected] Abstract—Anonymity in Bitcoin, a peer-to-peer electronic currency system, is a complicated issue. Within the system, users are identified by public-keys only. An attacker wishing to de-anonymize its users will attempt to construct the one-to-many mapping between users and ... List of computer science publications by Fergal Reid. refinements active! zoomed in on ?? of ?? records. dismiss all constraints. view refined list in Anonymity in Bitcoin, a peer-to-peer electronic currency system, is a complicated issue. Within the system, users are identified by public-keys only. An...

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