Cryptocurrency Blockchains Don’t Need to Be Energy Intensive

Re:Cryptocurrency Blockchains Don’t Need to Be Energy Intensive by skybrian on Monday July 05, 2021 @01:01PM (#27739853)

How do you know you have the longest chain without having all the blocks? You need to reach consensus on which blocks exist, and you can't get that without talking to enough other nodes to be pretty sure you have enough blocks that a longer chain is unlikely.

When there is a network split, nodes on one side of the split might think they have the longest chain and be wrong about it. Unless you know you have most of the computing power on your side of the network split, you can't really know which side has the longest chain until the network split is over.

So no, Bitcoin doesn't avoid the need to achieve consensus.

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Re:Cryptocurrency Blockchains Don’t Need to Be Energy Intensive by kerkeslager on Monday July 05, 2021 @05:49PM (#27742146)

Glad we've come to the conclusion that things I didn't say aren't true!

What I actually said is, "[I]f you're only connected to two nodes and those two nodes are showing you two different spends of the same balance, you have no way to resolve that conflict. In PoW (a real proof algorithm) you simply look at the longer chain."

You're correct that this isn't a proof of consensus.

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Re:Cryptocurrency Blockchains Don’t Need to Be Energy Intensive by skybrian on Monday July 05, 2021 @08:26PM (#27743121)

Fair enough. But looking at the longest chain you have (from the two nodes you can connect to) and assuming it's valid is not sufficient. You also need some reason to believe there isn't a longer chain out there. (In practice this is by waiting for a certain number of "confirmations.")

Maybe that's assumed in "simply look at the longer chain" but I thought I'd point it out.

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