Resources
People often ask me "How did you learn how to hack?" The answer: by reading. This page is a collection of the blog posts and other articles that I have accumulated over the years of my journey. Enjoy!
- Ethereum has implemented several EVMs and consensus clients, which is important for security. If there's a horrible double-spend issue, it's unlikely that it will be on two different clients. Unfortunately, this has created an entirely new bug class: consensus disagreements. If two implementations differ at all, then these two stacks will come to different conclusions on values, resulting in a chain split.
- Geth and Nethermind are two such EVM implementations. A competitor in the Pectra Audit contest noticed that there is a difference in the results of the BLS12-381 pre-compile. The specification for this smart contract had the following: "If any input is the infinity point, pairing result will be 1. Protocols may want to check and reject infinity points prior to calling the precompile."
- This has two interpretations:
- The pair may be ignored, where P or Q is infinity.
- The precompile should return 1 and the multi-pairing shouldn't be computed.
- The author intended 1. Nethermind had implemented 2, and Geth had implemented 1. So, it was decided to use the Geth-compliant implementation in this case. Consensus issues are super nasty; they quickly lead to the division of chains. Unfortunately, it's nearly impossible to be perfectly compliant with every little feature of a piece of software.
