How Bitcoin Rewired a Classic Computer Science Problem (ft. Tim Roughgarden and Ittai Abraham)

**Ittai Abraham** (0:00)
So, this was in 2007 I was at a workshop, and the goal of the workshop is to kind of see whether Byzantine fault tolerance is practical or not. But there was actually two big complaints. One is that maybe nobody needs it, and the other was that the performance was horrible.

**Tim Roughgarden** (0:11)
So, the question wasn't whether consensus protocols are practical. The question was, did you really need to be robust to potentially very unpredictable failures, as opposed to just crashing?

**Ittai Abraham** (0:22)
Satoshi Nakamoto, he kind of realized that. He said the core technical aspect of Bitcoin is solving Byzantine agreements. I would say de facto all the major chains that we know are running some version of Byzantine thought tolerance. The early proof of stake protocols, they were not very efficient. They had blocks every 10 minutes. And so really, if you're thinking about serving billions of people or systems that really manage large economies, you want to have kind of a wartime mode and a peacetime mode. So in peacetime, there's no failures. And the thing is that you do want to be able to switch to wartime. So if you are under attack, then you do have a way to kind of overcome a massive attempt to corrupt your system.

**Tim Roughgarden** (1:05)
Hi, everyone, I'm Tim Roughgarden, Head of Research at A16z Crypto and Professor of Computer Science at Columbia University. And today, we're kicking off a new series called First Principles, The Scientific Roots of Blockchain Technology, that explores one of the most exciting areas of research at the intersection of theory and practice today, blockchains and where the ideas that make them possible come from. At their core are decades of work across computer science, economics and mathematics, ideas about how distributed systems reach agreement, how trust can emerge without central authority, and how computation can be verified across networks of strangers. So we'll trace these ideas from their origins to the systems running in production today. And we'll talk with the scientists and the scholars whose breakthroughs made it all possible. To start, we're going to focus on one of the deepest threads, which is distributed consensus. How many machines can agree on a shared state even in the presence of failures and adversarial behavior. Concepts like Byzantine agreement and state machine replication, developed decades ago now, sit at the heart of modern blockchain technology.
So to begin, I'm joined by A16z crypto research partner, Ittai Abraham. Ittai is one of the world's leading researchers in Byzantine agreement and consensus protocols. He's a founding member of VMware's blockchain project. He's also the founder of Decentralized Thoughts, one of the field's most respected and long-running technical blogs. Together, we unpack the work of two pioneers, Barbara Liskov and Leslie Lamport, whom you'll hear directly from in the episodes ahead.
So Ittai, very, very cool. We get to interview both Leslie Lamport and Barbara Liskov. It's a great honor. Really, really cool we get to do this.
Maybe for the audience benefit, we should talk a little bit about how the pioneering work that they did connects to blockchain technology. So the first blockchain that came out, Bitcoin, 2008, 2009, part of what it is is a consensus protocol. And so the question is, what does that mean? A lot of the work that Lamport and Liskov both did, it's way before Bitcoin. It's from the 90s, from the 80s, even earlier. What's the connection? Bitcoin is a consensus protocol, but there's also this classic work in consensus protocols. Was Bitcoin reinventing the wheel or how should we think about that?

**Ittai Abraham** (3:29)
Bitcoin was not just a whole new disruption in distributed computing, it also has innovation in economics and cryptography. But here we're going to focus on the distributed computing part.
It actually took quite a few years for people to realize that this is kind of solving a Byzantine agreement problem. So Byzantine agreement problem is kind of this very core academic problem that has been studied for 40 years. In that sense, Bitcoin is kind of this huge revolution in how to solve Byzantine agreement. In fact, if you look at early emails from Satoshi Nakamoto, he kind of realized that. So he said, the core technical aspect of Bitcoin is solving Byzantine agreement.

**Tim Roughgarden** (4:03)
So Nakamoto apparently knew that this was a well-known problem in distributed computing. So what's the connection then between the Bitcoin protocol and the protocols we're going to hear about?

**Ittai Abraham** (4:14)
Yeah, so in a sense, both the protocols that we're going to hear about from Barbara Liskov and Leslie Lamport are Byzantine agreement protocols or agreement protocols in general. So Bitcoin solved this in a much different setting, permissionless with a much smaller setup, much more kind of a gear towards cryptocurrency and crypto economics.