This piece is the second in our series on the Ethereum supply chain. In Part 1, we covered the evolution of the supply chain to date and the justifications for proposer-builder separation (PBS). We also explored some issues that the current reliance on out-of-protocol relays has led to, and how various design decisions have led to centralizing tendencies up and down the stack.
In this part, we explore Enshrined Proposer-Builder Separation (ePBS), a high-level proposal to protocolize PBS and avoid the negative effects of out-of-protocol relays. First, we recap the reasons to enshrine PBS. Then, we define the design goals for ePBS, analyze the proposals themselves, and examine dependencies that may affect potential implementations of ePBS.