It's a shame nobody ever thought to ask this question in the past. Then we wouldn't have to try and figure out such a complicated concept today.
Just for fun, lets see what a quick Google search turns up?
Nodes (once again ALL NODE not just miners) use the longest (most work) VALID chain.
But then, what's the legitimate branch of the chain?
That is determined by what in Bitcoin terms would be "the
most work".
- snip -- snip -
This attack does not exist because Bitcoin chooses the chain with the most work, not the most blocks.
- snip -
bitcoin uses a cryptographic proof of work with a most-work-wins approach to double-spend resolution.
- snip -
- snip -
* Longest technically means the most work not necessarily the most blocks as Bitcoin selects as the primary chain the one with the highest collective difficulty.
- snip -
The Bitcoin client will accept the "longest chain", which is the chain with the most work behind it.
- snip -
- snip -
Client trusts the longest (most work) chain,
- snip -
- snip -
The bitcoin protocol specifies that in the case of a blockchain fork the winning chain is the one with the most work in it.
- snip -
Wow. It's almost like there's an actual reason that the system is called "
proof-of-work". As if it's necessary to somehow provide cryptographic
proof that your chain involved the most
work in order to be considered to be the current consensus chain.