Since the advent of the internet, programmers have been trying to figure out how to create a [digital] world in which people anywhere - even complete strangers - can transact directly with one another safely and efficiently. In essence, they have been trying to recreate the bedrock of civilization: an orderly system of bookkeeping that allows people to trust each other's claims about what they own, what they owe, and what they are owed. For most of the digital age, this “trust” has been facilitated by third parties such as banks, governments, or credible companies that are willing to guarantee that a transaction is valid and secure. But transactions via third parties are slow and expensive, and they cannot be verified by just anyone, which opens the door to fraud and theft.

Today, the notion of a secure and trusted third party in a digital world isn't purely mythical. And in fact, it's exactly what blockchain technology embodies in a kind of magical way. In this course, you will explore the mechanics of blockchain technology and how the blockchain acts like a trusted third party. To do this, Professor Ari Juels will design a theoretical cryptocurrency from scratch to illustrate how Bitcoin and other cryptocurrencies make use of the blockchain to transfer value from person to person. Then, once you understand how the blockchain acts as a trusted ledger, you will practice articulating other transformative ways in which blockchains can change how commercial and interpersonal connections happen online.