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!

The term proof is used for loosely in the blockchain industry. Originally with Bitcoin, proof of work was used as an anti-spam technique. It relies on the probabilistic assumption takes a certain amount of time to find the correct pre-image of a hash. Hashes are sufficiently random so this is fairly reasonable. Based on all previous data, there's no reason this won't work in the future. It makes this for deductive than inductive.

Proof of Stake was popularlized by Tendermint. "Proof" relies on a majority of cryptographic validators (two-thirds power). With proof of stake, the current block is grounded in the previous one. All though the name implies some mathematical deduction, this is NOT a regular proof. This makes all of the blocks sequential to the other blocks.

Light clients follow the same logic, except they start with a trusted block that is provided at the beginning of the light client. Additionally, they can skip blocks with "Non-adjacent block verification" assuming that 2/3 from the most recent trusted block have signed on this block. Giuseppe doesn't like this. Why?

Two large induction leaps are being made:

• Any validator holding 1/3+ of the voting power at block height H continues to behave honestly for N blocks.
• Validator from the first point is no longer trusted at H+N.

Because the validator is trusted from Height H + N blocks, if they decide to be malicious for a period of time their proof is still technically valid! It doesn't matter that they were slashed on the other chain; it's still valid from the perspective of the light client. The consequences of not having perfectly sequential block validation is not great given the argument. But, to my knowledge, no hacks surrounding this have happened yet.

According to the author Skipping verification for non-adjacent blocks might very well be named "Proof of Faith" or, better, "Proof of Nothing". Interesting post around the design of Tendermint light client verification!