Since its launch in 2009 much has been written about Bitcoin, cryptocurrencies and blockchains. While the discussions initially took place mostly on blogs and other popular media, we now are witnessing the emergence of a growing body of rigorous academic research on these topics. By the nature...

Over the last few years, we have witnessed an upsurge of enthusiasm about cryptocurrencies and, more generally, the so-called blockchain technology. In this new and updated edition, the authors explore what exactly these new technologies entail and promise. They argue that to understand the...

In recent years, the designs of many new blockchain applications have been inspired by the Byzantine fault tolerance (BFT) problem. While traditional BFT protocols assume that most system nodes are honest (in that they follow the protocol), we recognize that blockchains are deployed in...

Permissionless blockchains were constructed with a view to being sustainably secure. At the heart of blockchain consensus mechanisms was an explicit cost (whether it be work or stake) for participation in the network and the opportunity to propose blocks that would be added to the blockchain. A...