Resilience against Intentional Risk inBlockchain Implementationsusing Complex Networks

Abstract

The title of this doctoral thesis is "Resilience against intentional risk in blockchainimplementations using complex networks". It is based on four pillars of knowledge:First, the world economy depends on data stored, processed and analysed by in-formation systems. Keeping these systems secure is of paramount importance. Allcomputers, from servers to handheld devices, especially those that hold databases, arevaluable targets to actors with malicious intentions. They aim to obtain either someillicit benefit or to provoke disruptions. The term cybersecurity refers to computersecurity. Intentional risk management takes care of analysing attacks on informationsystems [21].Second, complex network theory is a powerful field at the crossroad of mathemat-ics, physics, computer science, statistics and sociology, among many other disciplines.It describes systems composed of a multitude of elements that interact with eachother, mostly in a non-linear way [81, 2, 9].Third, blockchain technology implements a distributed ledger. A ledger is a databasethat registers transactions between accounts. A blockchain keeps the history of ex-changes as a list of records replicated in multiple locations to guarantee its integrity[116, 110]. A public blockchain allows any participant to join and leave the systemat any time. Private blockchains require prior authorisation to join. This doctoralthesis studies public blockchain implementations. Bitcoin (BTC) is the pioneer pub-lic blockchain implementation that inaugurated an entire new way to approach thetransfer of digital value [79]. Ethereum (ETH) is a public blockchain implementationwith an advanced scripting functionality [39]. Within the realm of public distributedledger implementations focused on the "Internet of Things" [72], IOTA [63] and Io-TeX [65] are front-runners that have considerable potential to grow.Fourth, the definition of resilience in psychology refers to the capacity to confrontadversity and to get out of it reinforced. In engineering, resilience in a material re-veals the capacity to absorb energy when deformed and to recover when the deformingforce ceases. In this doctoral thesis, I use complex network theory [81, 2, 9] to modelblockchain implementations and analyse their resilience against intentional risk.