Bitcoin Unlimited developer Andrew Stone looks at forks: Without breaking the basic currency function of Bitcoin, we will only follow the chain with the highest computing power

BIP109 released by Bitcoin Unlimited (BU) is highly compatible because it can accept all supersets within the scope of BIP109 ^[1] . It can accept larger blocks and more signature operations. So in essence, BIP109 is a "soft fork" within the capabilities of BU. Unfortunately, a client cannot support a superset of BIP109, so multiple options must be listed. Under the premise of 1MB block capacity, BU can produce superset blocks to support BIP109. At the same time, BUIP (BU Improvement Protocol) can also strictly update and improve BIP109 when necessary.

This form can bring inspiration to the consensus function of the entire network. Bitcoin is built on the principle of zero-trust. If we only rely on developers to create perfectly compatible software, then we are actually reintroducing the word trust without realizing it. In this way, the only difference between Bitcoin and traditional financial networks will only depend on personal preference (who you trust) rather than their philosophy. This is vividly demonstrated in Ethereum. Ethereum developers have become the decision makers of the entire network, and participants must trust them to conduct transactions.

This situation will never happen to BU. Even if the roles are reversed (if BU is the party with less computing power), the result will be the same.

Ask yourself, why do you think that Classic splitting off from the network is necessarily a "bad thing"? I think that's because even though the rules were broken, it wasn't serious enough to warrant a fork. Classic supporters will still choose to follow the main chain (the one with the highest hashrate) and won't care if the rules are broken.

From the perspective of zero-trust game theory, the client must follow the chain that is sufficient to maximize the value of the currency in the hands of the user. Therefore, the client can only fork if the value of the user's currency is damaged after a certain rule change.

BU does not just come up with excessive blocks and multi-party compatible algorithms, they are the best choice for reasonable software in a trustless network. In essence, they synchronize the choices and actions of the client, and if the client's choice is rejected, it can also listen to the majority opinion.

Therefore, BU's principle is to follow the chain where the majority of people are, unless the basic currency function of Bitcoin is destroyed, such as causing inflation, or users spending each other's coins, etc. These phenomena will cause the value of Bitcoin in the hands of users to be damaged, so a fork must be executed to protect the value of Bitcoin.

Currently, Bitcoin is still protected by a single client (trusted developers). But since last year, many people have accused this client of failing to provide the development functions that Bitcoin urgently needs. Given that Bitcoin exists in a decentralized multi-client environment, client developers must ask themselves: How important are the rules? If most miners break the rules, what should my client choose?

Notes (↵ returns to text)

1. If every element in a set S2 is also in a set S1, and set S1 may contain elements that are not in S2, then set S1 is a superset of S2.