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The majority of the hash power is in China. If China can seize the miners all at once, they'll have control over the blockchain. At that point, other countrie

by howlin 9y ago

The majority of the hash power is in China. If China can seize the miners all at once, they'll have control over the blockchain. At that point, other countries would be foolish to compete, and may focus on alternate alt currencies.

tboyd47 9y ago
But they still can't change the blockchain. And there would still be miners outside of China.
- XR0CSWV3h3kZWg 9y ago
  If you control 50 + epsilon percent of the hash power you can censor blocks at will. You can ignore every block that anyone else makes and still have the longest chain.
  - tboyd47 9y ago
    Except for the fact that they can still get confirmation from the other 50 - epsilon percent. Having 51% of hash power doesn't mean you mine 100% of blocks. That's not how Bitcoin works. With 51% you will probably mine around 51%.
    - Dylan16807 9y ago
      You're forgetting that every miner chooses how they mine. Someone with 51% hash power can decide to always mine on top of their previous block, ignoring what everyone else does. And because the 51% chain is longer, the 49% chain get discarded by any miner following default bitcoin rules. So the effective block rate gets slowed down, and the person with 51% of the power has control of 100% of the canonical blocks.
      - tboyd47 9y ago
        This would make the 51% miners' chain grow at half the speed as the 49% miners' chain, because the 49% are building on both their blocks and the other miners' blocks, whereas the 51% are only building on their blocks. This, of course, is assuming that the 51% doesn't create blocks considered invalid on the other chain. This would cause a hard fork and it's exactly what is happening now with Bitcoin Cash, except with a much smaller fraction than 51%. So no, what you are describing cannot happen with the default rules.
        Dylan16807 9y ago
        > the 49% are building on both their blocks and the other miners' blocks, whereas the 51% are only building on their blocks. They are building on some of their blocks and some of the other miner's blocks. This doesn't make them faster. Whenever a 49%er mines a block, there is a temporary fork. The 49% and the 51% start mining on two completely separate branches, both of which progress at half speed. Eventually the 51% branch is longer, and the 49% discard their previous work and switch to it. So the 49% were using their blocks, and now they are using the 51% blocks, but never both at the same time. The canonical blockchain does not progress at full speed. Half the blocks that get mined eventually become orphans. It would be impossible for the 49% to build on everyone's blocks, because the 51%-created blocks are always mutually incompatible preexisting 49%-created blocks. > This, of course, is assuming that the 51% doesn't create blocks considered invalid on the other chain. Yes, of course.
        tboyd47 9y ago
        If this were so then Bitcoin Cash would have been dead from the start. They hard forked with much less than 49% of hashpower. There are really two separate scenarios we're talking about here. Miner activated hard forks, which are a real thing that have happened (though not exactly like you describe), and a hypothetical situation where a group of miners agree to create an exclusive chain that is also backwards compatible. I'm no expert but I don't think that would have the intended result.
        Dylan16807 9y ago
- freeloop2 9y ago
  You can effectively freeze anyone's funds by refusing any transactions that originate from their address

by howlin 9y ago

tboyd47 9y ago

But they still can't change the blockchain. And there would still be miners outside of China.

XR0CSWV3h3kZWg 9y ago
If you control 50 + epsilon percent of the hash power you can censor blocks at will. You can ignore every block that anyone else makes and still have the longest chain.
- tboyd47 9y ago
  Except for the fact that they can still get confirmation from the other 50 - epsilon percent. Having 51% of hash power doesn't mean you mine 100% of blocks. That's not how Bitcoin works. With 51% you will probably mine around 51%.
  - Dylan16807 9y ago
    You're forgetting that every miner chooses how they mine. Someone with 51% hash power can decide to always mine on top of their previous block, ignoring what everyone else does. And because the 51% chain is longer, the 49% chain get discarded by any miner following default bitcoin rules. So the effective block rate gets slowed down, and the person with 51% of the power has control of 100% of the canonical blocks.
    - tboyd47 9y ago
      This would make the 51% miners' chain grow at half the speed as the 49% miners' chain, because the 49% are building on both their blocks and the other miners' blocks, whereas the 51% are only building on their blocks. This, of course, is assuming that the 51% doesn't create blocks considered invalid on the other chain. This would cause a hard fork and it's exactly what is happening now with Bitcoin Cash, except with a much smaller fraction than 51%. So no, what you are describing cannot happen with the default rules.
      - Dylan16807 9y ago
        > the 49% are building on both their blocks and the other miners' blocks, whereas the 51% are only building on their blocks. They are building on some of their blocks and some of the other miner's blocks. This doesn't make them faster. Whenever a 49%er mines a block, there is a temporary fork. The 49% and the 51% start mining on two completely separate branches, both of which progress at half speed. Eventually the 51% branch is longer, and the 49% discard their previous work and switch to it. So the 49% were using their blocks, and now they are using the 51% blocks, but never both at the same time. The canonical blockchain does not progress at full speed. Half the blocks that get mined eventually become orphans. It would be impossible for the 49% to build on everyone's blocks, because the 51%-created blocks are always mutually incompatible preexisting 49%-created blocks. > This, of course, is assuming that the 51% doesn't create blocks considered invalid on the other chain. Yes, of course.
        tboyd47 9y ago
        If this were so then Bitcoin Cash would have been dead from the start. They hard forked with much less than 49% of hashpower. There are really two separate scenarios we're talking about here. Miner activated hard forks, which are a real thing that have happened (though not exactly like you describe), and a hypothetical situation where a group of miners agree to create an exclusive chain that is also backwards compatible. I'm no expert but I don't think that would have the intended result.
        Dylan16807 9y ago
freeloop2 9y ago
You can effectively freeze anyone's funds by refusing any transactions that originate from their address