Re: Wall Observer BTC/USD - Bitcoin price movement tracking & discussion
The longest proof of work chain is the consensus mechanism.
You keep spreading this falsehood. While it is not exactly wrong, it's not perfectly right either.
Not really. "the longest chain" is ambiguous. It should really be "the longest valid chain", and then you need to define which coin's concept of "validity" you're using. Every client follows the longest valid chain - that's precisely how they decide which chain to follow.
So assuming the question is "will my node follow the longest valid Bitcoin chain?", then the answer is "no" for XT once BIP101 is activated. At that point XT stops following the longest valid Bitcoin chain and starts following the longest valid XT chain, whereas the answer is "yes" for Bitcoin.
It's my understanding that neither of these assertions is true in Bitcoin XT. XT changes the consensus mechanism significantly:
Another less cited new feature of the XT client is a change to chain selection/consensus rules. XT clients don't follow the longest chain, they follow the chain with the highest XT checkpoint embedded into it.
Exactly what is a checkpoint and how is it embedded in the blockchain?
How does the XT wallet decide which chain to embed a checkpoint into, and how does it decide what height to embed a checkpoint at?
How does the XT wallet decide the frequency and time to embed checkpoints at?
There is only one thing you really need to know: checkpoint is not Bitcoin.
Checkpoint is an attempt a rewriting history. One of Hearn's favorite tool.