Web3 Consensus Tutorial
Bill Laboon (Web3 Foundation)

Traditional proof-of-work blockchains such as Bitcoin and Ethereum are, by design, extremely inefficient in terms of energy usage, and allow for only probabilistic finality. Using other, traditional ways to come to consensus on distributed systems (such as Practical Byzantine Fault Tolerance) is more energy-efficient, but can be quite slow and even vulnerable to stalling in the event of severe network partitioning.

In Polkadot, these problems are ameliorated by using a hybrid consensus model. This divorces the mechanism of block production from block finalization, allowing blocks to be produced in all situations, but provably finalized later via a separate protocol. Block production uses the BABE (Blind Assignment for Blockchain Extension) protocol to produce blocks, which have an initial implicit probabilistic finality. Finality of blocks produced by BABE can then made permanent and provable by a separate finality gadget, GRANDPA (GHOST-Based Recursive ANcestor Deriving Prefix Agreement).

This session will go into deep details of how the BABE and GRANDPA protocols work, how they are used in Polkadot to produce and finalize blocks, and how together they can provide an extremely high-uptime, yet finalizable, production of a canonical history.

Bill Laboon is the Technical Education Lead for the Web3 Foundation in Zug, Switzerland, where he helps people understand blockchain technology. He is also a Lecturer (currently on a leave of absence) in the Computer Science Department of the University of Pittsburgh, after fifteen years in the software industry. He is a frequent speaker at conferences on a variety of topics, including blockchain technology, improving software quality, and the ethics of software development. He is the author of two books: A Friendly Introduction to Software Testing, an undergraduate textbook; and Strength in Numbers, a near-future novel set in a world in which cryptocurrency has entirely eliminated traditional money.