We were first introduced to Bitcoin in October 2011. At that time, both Elli and I were conducting our post-doctoral research at ETH Zurich. We were reading several media articles mentioning Bitcoin, and were rather curious about the underlying system. A specific article caught our attention at that time: Bitcoins were accepted as a form of payment in a fast-food restaurant in New York. We were not surprised by the fact that people were using Bitcoin for real payments; it is true that we did not really believe in Bitcoin at that time. We believed that Bitcoin was an interesting protocol allowing computer geeks to make money by running a program on their PC. Our surprise was mainly that Bitcoin—in which a transaction takes almost an hour to be confirmed—was used to handle fast payments! We decided to immediately write a paper to warn the community from such usage of Bitcoin; in our paper, we showed analytically and experimentally that double-spending in Bitcoin can be easily realized in the network on unconfirmed transactions. At that time, we bought 10 Bitcoins with 5 Swiss Francs and I remember thinking: “These Bitcoins are really expensive” (I wish I knew better.) Our paper was published at ACM CCS 2012, which is one of the most prestigious computer security conferences in the world. We additionally proposed some countermeasure to allow fast payments with minimal risk of double-spending; our countermeasure was eventually integrated in Bitcoin XT.
From that point on, we delved into researching Bitcoin. This resulted in a number of papers that appeared at top security and privacy conferences; the first few lines in our introductions would evolve from “Bitcoin is receiving considerable attention in the community” to something that turned out to be a big surprise to us as well: “Bitcoin has received more adoption than any other digital currency proposed to date.”
Five years after our first research paper on Bitcoin (during which we published eight research papers on Bitcoin at top security venues), we decided that it was time to share our Bitcoin experience, and the various lessons that we learned with a broader audience.
This book is mostly intended for computer scientist/engineers and security experts. If you are interested in Bitcoin, and you do have general computer science knowledge, this book will teach you all that you need to know about the security and privacy provisions of Bitcoin.
Dr. Ghassan Karame