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Comment by Expez | Hacker News Reader

Here's a quote from the conclusion of the whitepaper in which Nakamoto laid out Bitcoin:

They vote with their CPU power, expressing their acceptance of valid blocks by working on extending them and rejecting invalid blocks by refusing to work on them. Any needed rules and incentives can be enforced with this consensus mechanism.

This is Bitcoin's consensus mechanism and it's called Nakamoto consensus.

In turn, this means that 'Bitcoin' is whatever chain has the most cumulative work done to secure it.

Nothing is 'contentious' about this. It either has the most cumulative PoW, or it doesn't.

If the minority chain has some value it might survive. If it does, that's fine. You'll have coins on both chains and you can choose to care or not.

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Longest PoW being the main chain was not described in the context of contentious changes to consensus code. By that definition, a 51% attack that censors transactions would be the longest PoW and be defined as 'Bitcoin'. The great thing about Bitcoin is that the users are able to each make their own decision on what Bitcoin is. Bitcoin needs to be anti fragile and will constantly be under these attacks, because if it fails, we need something better.

This is all new territory and the appeal to authority by citing the white paper is less helpful than most people believe.

You're absolutely correct. The 51% example that you bring up would be an undesirable outcome (from our PoV), but the incentives are in place to ensure that it is extremely unlikely to ever happen.

Distributed consensus is a non-trivial problem, and for sure certain tradeoffs were made by Satoshi to make it both distributed and permission-less.

Unless you want a benevolent dictator of some sort all you can do is set up a system that's robust from a game theory perspective.

Sure, but if the winning fork turns out to be unmaintained or suffer some devastating replay attack, Bitcoin as a whole suffers. It's possible for the consensus mechanism to be used towards an objectively bad system.

And sure, that's part of how the consensus mechanic was always meant to fuction. DAO contracts were meant to be irreversible too, but that didn't stop people from being sad and seeking a change when they were robbed.

But satoshi's vision was that every computer can run the software to vote for the chain they want. Majority of hashrate today is controlled by a single company Bitmain.

Also Segwit2x are trying to kill the current bitcoin chain. I wont have a problem with them if they had a replay protection but putting users in danger is contentious.

Every single sentence you wrote contains a factual error.

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> [...] acceptance of valid blocks [...]

that is the point. B2X-blocks are not valid blocks for the regular BTC-Nodes, because some of the Blocks will have a block-weight > 4000

Non-mining nodes do not get a vote in Nakamoto's consensus model. That is by design.

They have to make a choice on what chain to follow just all other actors on the network. Doing nothing is a valid choice of course, but it might not bring you a desirable outcome.

They have an economic vote (I do not accept B2X-coins).

If there is consensus, then all these nodes add up and have a very big economic vote!

Many people seem to forget that Bitcoin is not pure software. It is a bit more!

edit: typo

Your accepting coins on one fork or the other won't have any bearing what so ever one which chain has the most cumulative PoW.

The only way you can influence which chain is the longest, without mining, is to pick a preferred chains and sell your coins on the other chain. That is your 'economic vote'.

If enough people do that, one chain will be way more profitable than the other and miners will switch over.

I agree. PoW is critical for minting a currency. I hope (and bet) that Bitoin Cash is Bitcoin.

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