Introduction to Consensus (Part I) with Andrew Lewis-Pye | a16z crypto research talks

TL;DR

The analysis covers the concept of consensus protocols in a synchronous setting with and without a public key infrastructure (PKI), discussing the issues of Byzantine agreement and broadcast. A two-step sub protocol called "Great Cast" is introduced, along with the Phase King Protocol that solves the Byzantine Agreement problem when f is less than n/3.

Transcript

all right so I think we're ready to go so today we have uh Andy Lewis five from London School of Economics going to be talking about consensus um and I'll just remind that we do have two more seminars this week tomorrow we have uh thing Wren who's visiting he's going to talk about bft protocols and uh I believe Thursday we have Andy again yeah yeah... Read More

Key Insights

• 🗂️ Consensus protocols can be divided into permissionless and permission protocols, with renewed interest in permission protocols due to potential implementations as permissionless protocols.
• #️⃣ The Phase King Protocol solves the Byzantine Agreement problem when the number of faulty processors is less than n/3.
• ⚾ The "Great Cast" sub protocol is a simple two-step process that aggregates values sent by processes and assigns grades based on the number of distinct values.
• 🈴 The Phase King Protocol ensures agreement by examining the grades assigned to each process and outputting the value with the highest grade.

Questions & Answers

Q: What is the difference between permissionless and permission protocols?

Permissionless protocols allow anyone to join and participate, while permission protocols require specific authorization to participate. Permission protocols are often used in situations where it is important to know the exact participants involved.

Q: Why is there renewed interest in permission protocols?

There is renewed interest due to the potential implementation of permission protocols as permissionless protocols. Additionally, certain methods allow the implementation of permission protocols as permissionless protocols, such as proof of stake protocols.

Q: What is the Phase King Protocol?

The Phase King Protocol is a consensus protocol that solves the Byzantine Agreement problem when the number of faulty processors is less than n/3. It involves a two-step sub protocol called "Great Cast" and assigns grades (0, 1, or 2) based on the number of distinct processes that send the same value.

Q: How does the Phase King Protocol ensure agreement in the presence of faulty processors?

The Phase King Protocol ensures agreement by using the "Great Cast" sub protocol to gather information about values sent by other processes. By examining the number of distinct processes that send the same value, the protocol assigns grades and determines the agreed-upon output value.

Summary & Key Takeaways

• The content discusses consensus protocols in a synchronous setting, focusing on the concepts of Byzantine agreement and broadcast.

• The distinction between permissionless and permission protocols is explained, with a renewed interest in permission protocols due to their potential implementation as permissionless protocols.

• The content provides a two-step sub protocol called "Great Cast" and introduces the Phase King Protocol, which can solve the Byzantine Agreement problem when the number of faulty processors is less than n/3.