An active research trend is to exploit the consensus mechanism of cryptocurrencies to secure the execution of distributed applications. In particular, some recent works have proposed fair lotteries which work on Bitcoin. These protocols, however, require a deposit from each player which grows quadratically with the number of players. We propose a fair lottery on Bitcoin which only requires a co...

Protecting software copyright has been an issue since the late 1970’s, and software license validation has been a primary method employed in an attempt to minimise software piracy and protect software copyright. This paper presents a novel method for decentralised peer-topeer software license validation using cryptocurrency blockchain technology to ameliorate software piracy, and to provide a m...

Since its 2008 appearance as a cornerstone of the cryptocurrency bitcoin, the blockchain technology gained widespread attention as a modality to securily validate and store information without a trusted third party. Indeed trust is replaced by cryptographic security, epitomised by hash functions, a unique fingerprint of any information file. The paper is a quick overview of the main concepts an...

We study cryptocurrency protocols that do not make use of Proof of Work. Such protocols commonly rely on Proof of Stake, i.e. on mechanisms that extend voting power to the stakeholders of the system. We offer analysis of existing protocols that have a substantial amount of popularity. We then present our novel pure Proof of Stake protocols, and argue that the they help in mitigating problems th...

Bitcoin exchanges are a vital component of the Bitcoin ecosystem. They are a gateway from the classical economy to the cryptocurrency economy, facilitating the exchange between fiat currency and bitcoins. However, exchanges are also single points of failure, operating outside the Bitcoin blockchain, requiring users to entrust them with their funds in order to operate. In this work we present a ...

We propose Mixcoin, a protocol to facilitate anonymous payments in Bitcoin and similar cryptocurrencies. We build on the emergent phenomenon of currency mixes, adding an accountability mechanism to expose theft. We demonstrate that incentives of mixes and clients can be aligned to ensure that rational mixes will not steal. Our scheme is efficient and fully compatible with Bitcoin. Against a pas...

In many real-world applications, sensitive information must be kept in log files on an untrusted machine. In the event that an attacker captures this machine, we would like to guarantee that he will gain little or no information from the log files and to limit his ability to corrupt the log files. We describe a computationally cheap method for making all log entries generated prior to the loggi...

We show how third-party web trackers can deanonymize users of cryptocurrencies. We present two distinct but complementary attacks. On most shopping websites, third party trackers receive information about user purchases for purposes of advertising and analytics. We show that, if the user pays using a cryptocurrency, trackers typically possess enough information about the purchase to uniquely id...

Bitcoin, a decentralized cryptocurrency, has attracted a lot of attention from academia, financial service industry and enthusiasts. The trade-off between transaction confirmation throughput and centralization of hash power do not allow Bitcoin to perform at the same level as modern payment systems. Block Advertisement Protocol is proposed as a step to resolve this issue. The protocol allows bl...