Comment by dsr_ | Hacker News Reader

Comment by dsr_ | Hacker News Reader

" Any distributed consensus system on the Internet must sacrifice one of these features."

is incomplete: a distributed consensus system (which is, at heart, a distributed database) can not have all three features... but there is no guarantee that a distributed database has any of those features.

As with everything else, execution matters.

If you're going to be recording history for financial transactions, you need to put immutability as your first goal. This is not compatible with unlimited space-time separation of trusted inputs, so the second thing you need is to decide how you're going to resolve inconsistent histories. Doing so always involves a centralized trusted system, even if it is fed from a distributed system: someone needs to decide what transactions really happened. You can claim that you have a distributed algorithm to do so (consensus) but that itself will always fall into the same distribution problem.

And that's what seems to have happened here.

> ...how you're going to resolve inconsistent histories. Doing so always involves a centralized trusted system

False, the Bitcoin system resolves inconsistent histories in a completely decentralized manner.

One could argue that a block chain fork could invalidate an arbitrary number of blocks at any time, and therefore the Bitcoin protocol does not by itself have this property of being able to tell which transactions really happened.

To limit the number of blocks that could be invalidated in this way, the bitcoin reference implementation contains checkpoint hashes. These are indeed decided centrally.

If you accept the core assumption in bitcoin that an attacker will never control a majority of the hashing power, then there probably isn't a problem and the checkpoint s aren't needed.

Each block chain fork is in essence a difference currency, and so you can tell which transactions happened for a given currency. Which currency is the favored one depends on the client hence the user. The users then just need to make sure that they are selecting the currency that they want to select.

The checkpoint hashes are not imposed on the users, but rather the users must choose to upgrade to the new checkpoint hashes. As such, you can argue that it is decentralized.

"One could argue that a block chain fork could invalidate an arbitrary number of blocks at any time, and therefore the Bitcoin protocol does not by itself have this property of being able to tell which transactions really happened."

No, one could not argue that. The economic majority will decide which fork is valid. That's the opposite of centralization.

"To limit the number of blocks that could be invalidated in this way, the bitcoin reference implementation contains checkpoint hashes. These are indeed decided centrally.

If you accept the core assumption in bitcoin that an attacker will never control a majority of the hashing power, then there probably isn't a problem and the checkpoint s aren't needed."

You fail to realize you are not forced to download anything you don't want to. And the checkpoints are hundreds of blocks deep. They don't decide anything the network hasn't already decided (6 blocks deep transactions are considered practically irreversible). The checkpoints ARE needed as an anti-DOS measure (they protect the storage of full nodes from being flooded by forks that could suddenly start to appear at low block numbers). I don't know why people are so eager to spit opinions on things they don't know anything about.

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