Zero-confirmation transactions, i.e., transactions that have been broadcast but are still pending to be included in the blockchain, have gained attention in order to enable fast payments in Bitcoin, shortening the time for performing payments. Fast payments are desirable in certain scenarios, for instance, when buying in vending machines, fast food restaurants, or withdrawing from an ATM. Despi...

We propose Mixcoin, a protocol to facilitate anonymous payments using the Bitcoin currency system. We build on the emergent phenomenon of currency mixes, adding an accountability mechanism to expose theft. Unlike other proposals to improve anonymity in Bitcoin, our scheme can be deployed immediately with no changes to Bitcoin itself. We demonstrate that incentives of mixes and clients can be al...

Bitcoin, the latest Internet phenomenon branded as a game-changer. It is a revolution in financial system and money creation mechanics which currently holds the market of almost 13 billion USD. At the same time, its inner working is presented as hard to understand but perfectly trustworthy and safe. This trust is what gives Bitcoin value, however due to its mystical creator and recent headlines...

Heretofore the concept of “blockchain” has not been precisely defined. Accordingly the potential useful applications of this technology have been largely inflated. This work sidesteps the question of what constitutes a blockchain as such and focuses on the architectural components of the Bitcoin cryptocurrency, insofar as possible, in isolation. We consider common problems inherent in the desig...

Bitcoin has emerged as the most successful cryptographic currency in history. Within two years of its quiet launch in 2009, Bitcoin grew to comprise billions of dollars of economic value, even while the body of published research and security analysis justifying the system’s design was negligible. In the ensuing years, a growing literature has identified hidden-butimportant properties of the sy...

Bitcoin is a cryptocurrency attracting a lot of interest both from the general public and researchers. There is an ongoing debate on the question of users’ anonymity: while the Bitcoin protocol has been designed to ensure that the activity of individual users could not be tracked, some methods have been proposed to partially bypass this limitation. In this article, we show how the Bitcoin trans...

This study provides a comparative financial and statistical analysis between the largest and most traded cryptocurrencies. In particular, the exchange rates of Bitcoin, Litecoin, Ripple and Ethereum were collected from August 2010 until May 2017. The raw annualized volatility of cryptocurrencies is compared as well as to fiat currencies and major exchange rates. The results show that Bitcoin is...

Bitcoin provides only pseudo-anonymous transactions, which can be exploited to link payers and payees – defeating the goal of anonymous payments. To thwart such attacks, several Bitcoin mixers have been proposed, with the objective of providing unlinkability between payers and payees. However, existing Bitcoin mixers are not under widespread use, and can be regarded as either insecure or ineffi...

The Bitcoin digital crypto-currency has evolved from niche financial technology to major currency, with a market capitalization of $94 billion at the time of this writing. All Bitcoin activity is tracked in a blockchain ledger which maintains a complete history of every Bitcoin transaction. This complete history offers a unique opportunity to analyze the peer-to-peer interactions within the Bit...

We study a model of fairness in secure computation in which an adversarial party that aborts on receiving output is forced to pay a mutually predefined monetary penalty. We then show how the Bitcoin network can be used to achieve the above notion of fairness in the two-party as well as the multiparty setting (with a dishonest majority). In particular, we propose new ideal functionalities and pr...