The Bitcoin ecosystem has suffered frequent thefts and losses affecting both businesses and individuals. Due to the irreversibility, automation, and pseudonymity of transactions, Bitcoin currently lacks support for the sophisticated internal control systems deployed by modern businesses to deter fraud. To address this problem, we present the first threshold signature scheme compatible with Bitc...

While threshold signature schemes have been presented before, there has never been an optimal threshold signature algorithm for DSA. Due to the properties of DSA, it is far more difficult to create a threshold scheme for it than for other signature algorithms. In this paper, we present a breakthrough scheme that provides a threshold DSA algorithm that is efficient and optimal. We also present a...

Im vorliegenden Paper wird die erste großangelegte NutzerInnenstudie zu Bitcoin vorgestellt. Dabei wird untersucht, wie die NutzerInnen das Bitcoin-Ökosystem im Hinblick auf Sicherheit, Datenschutz und Anonymität bewerten. 990 Bitcoin-NutzerInnen wurden mittels Online-Fragebogen befragt, um Strategien der Bitcoin-Verwaltung zu identifizieren und festzustellen, welche Sicherheitsmaßnahmen Nutzer...

We present Catena, an efficiently-verifiable Bitcoin witnessing scheme. Catena enables any number of thin clients, such as mobile phones, to efficiently agree on a log of applicationspecific statements managed by an adversarial server. Catena implements a log as an OP_RETURN transaction chain and prevents forks in the log by leveraging Bitcoin’s security against double spends. Specifically, if ...

This paper presents an extension to Bitcoin’s script language enabling covenants, a primitive that allows transactions to restrict how the value they transfer is used in the future. Covenants expand the set of financial instruments expressible in Bitcoin, and enable new powerful and novel use cases. We illustrate two novel security constructs built using covenants. The first, vaults, focuses on...

The Bitcoin virtual currency is built on the top of a decentralized peer-to-peer (P2P) network used to propagate system information such as transactions or blockchain updates. In this paper, we have performed a data collection process identifying more than 872000 different Bitcoin nodes. This data allows us to present information on the size of the Bitcoin P2P network, the node geographic distr...

The Bitcoin cryptocurrency system relies on a novel distributed consensus mechanism relying on economic incentives. It is often argued that Bitcoin is “incentive-compatible” in simplified models; that is, that the scenario in which all miners follow the Bitcoin protocol is a stable Nash Equilibrium in which no miner has any incentive to defect. We introduce the notion of a bribery attack in whi...

The Bitcoin system is an anonymous, decentralized crypto-currency. There are some deanonymizating techniques to cluster Bitcoin addresses and to map them to users’ identifications in the two research directions of Analysis of Transaction Chain (ATC) and Analysis of Bitcoin Protocol and Network (ABPN). Nowadays, there are also some anonymization methods such as coin-mixing and transaction remote...

We describe a new methodology that enables the direct execution of multi-threaded applications inside of Shadow, an existing parallel discrete-event network simulation framework. Our methodology utilizes function interposition and an application-layer thread library to emulate the ordinary thread interface to the application. Using this methodology, we implement a new Shadow plug-in that direct...

We present atomic trade protocols for Bitcoin and Ethereum that can bind two parties to swap coins in the event that two blockchains emerge from a single “pre-fork” blockchain. This work is motivated by a bet between two members of the Bitcoin community, Loaded and Roger Ver, to trade 60,000 bitcoins in the event that Bitcoin Unlimited’s planned hardfork occurs and the blockchain splits into tw...