| Your solution regularly leads to orphans 5 blocks deep, making the network unstable. Now consider this: - Chinese miners (the network doesn't know that) publish a normal transaction. - they don't include it for 30 blocks. Western nodes have already switched to a minority uncensored chain after 5 blocks, as they consider the transaction censored. - Chinese miners include it in 31st block. A new node joins. It follows the Chinese chain indefinitely. The core of the problem is lack of objective time (or at least ordering): there's no way to prove to the new node that a transaction was actually censored in the past. From its perspective, the minority chain might have been created after the Chinese block with the transaction was published. As long as there's no external objective time, it's always possible to invent some attack scenario that splits the network for new nodes. Last but not least, every minority chain is by definition vulnerable to 51% attacks, so even if a solution to censorship could exist in PoW, the minority chain could get intentionally killed this way, constantly generating double spends until people stop using it. |
Only if China decides to hamper the speed of their miners by pointlessly trying unsuccessfully to censor transactions.
> - Chinese miners (the network doesn't know that) publish a normal transaction.
> - they don't include it for 30 blocks. Western nodes have already switched to a minority uncensored chain after 5 blocks, as they consider the transaction censored.
> - Chinese miners include it in 31st block.
> A new node joins. It follows the Chinese chain indefinitely.
Okay, yes. And so does the entire rest of the network, because now the blocks are valid. Yes, this is very bad, because anyone who spent money in the shorter chain can now re-spend their coins.
But critically, nothing was censored here. This is a transaction reordering, not a censorship attack.
China can do the exact same thing with fewer steps. All they have to do is go back 30 blocks, and start mining blocks with the transactions in whatever order they want. Eventually their branch will be ahead and everyone will switch to it.