That is my limited understanding of BU. In fact I believe I was the one (as part of an interaction with Peter R) on the GcBU thread who pointed out that the satoshi whitepaper can be read as effectively miners making all the rules on what constitutes a valid block. End user nodes would also implement verification for protection against short term chain forks, but they would validate based on rules set entirely by miners. So as an end user, if miners change the rules, you would simply need to implement those changes in your node, or you would be unable to process the longest chain, and therefore no longer a participant.

This is certainly a different security model than what many in the Bitcoin community have come to understand over the past several years, where forks are accepted by an "economic majority" and "longest chain" is replaced with "longest valid chain". But it seems that (maybe) BU proponents want to adopt a stricter "longest chain" rule that vests all of the rule-making power with miners. I'm neither agreeing nor disagreeing here; I'm trying to state the position to see if I understand it.

Now in the case of BU specifically, I'm not sure I understand how this works when the user has configured a smaller block limit than is present on the longest chain? Does their node switch into an "offline" state based on block headers? The user then has a choice to adjust their setting (and network bandwidth, etc.) or stay off the network?


As I understand it, the rule is solely set by proof-of-work (i.e. large sum off difficulty). Any node that is off the chain with the most work is considered off the network. In that case it would be sybil proof, because proof-of-work can't be replicated. Let's see if I'm right.