The advent of new digital currencies has challenged our notions about money, its function and purpose, and our faith in the financial and banking structures that underpin its legitimacy. Oonagh McDonald examines the challenges, opportunities and threats that cryptocurrencies pose to existing fiat currencies and their potential to change how global finance operates. From Bitcoin to Facebook's Diem, the book charts the spectacular rise of cryptocurrencies over the past decade alongside the much slower regulatory response. It assesses the potential of the technology underpinning new digital currencies - blockchain, digital tokens and smart contracts - to evade existing regulatory frameworks and considers the need for more robust protection from fraudulent initial coin offerings, scams and hacks. The book examines the motivations of central banks as they begin to explore opportunities for an alternative global digital currency, and what this might mean for the supremacy of the dollar and other fiat currencies. The future of cash is also considered. Throughout her analysis, McDonald shows that trust is fundamental to the operation of finance and that this will ultimately protect commercial bank money from the threat of new digital currencies. The book offers readers an insightful appraisal of the future of money and the challenges facing regulatory bodies.