Database and Distributed Computing Foundations of Blockchains by Amr El Abbadi

Bitcoin is a successful and interesting example of a global scale peer-to-peer cryptocurrency that integrates many techniques and protocols from cryptography, distributed systems, and databases. The main underlying data structure is blockchain, a scalable fully replicated structure that is shared among all participants and guarantees a consistent view of all user transactions by all participants in the cryptocurrency system. The novel aspect of Blockchain is that historical data about currency transactions is maintained in the absence of any central authority. This property of Blockchain has given rise to the possibility that future applications will transition from centralized databases to a fully decentralized storage based on blockchains. In this tutorial, we discuss the basic protocols used in blockchain, and elaborate on its main advantages and limitations. To overcome these limitations, we provide the necessary distributed systems background in managing large scale fully replicated ledgers, using Byzantine Agreement protocols to solve the consensus problem. The focus of the tutorial is on the distributed systems and database aspects of the recent innovations in blockchains.