[bitcoin-dev] Centralizing mining by force

[Robert Taylor <roberttaylorgen@gmail.com>]

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Forgive me if this has been asked elsewhere before, but I am trying to
understand a potential failure mode of Bitcoin mining.

A majority of miners can decide which valid blocks extend the chain. But
what would happen if a majority of miners, in the form of a cartel decided
to validly orphan any blocks made by miners outside of their group? For
example, they could soft fork a new rule where the block number is signed
by set of keys known only to the cartel, and that signature placed in the
coinbase. Miners outside of the cartel would not be able to extend the
chain.

It would be immediately obvious but still valid under the consensus rules.
What are the disincentives for such behavior and what countermeasures could
be done to stop it and ensure mining remained permissionless? I think this
is a valid concern because while it may not be feasible for one actor to
gain a majority of hash alone, it is certainly possible with collusion.

Robert

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