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Comment by sgjohnson | Hacker News Reader

> - nobody owns Bitcoin network => delivered;

For a state actor it would actually be quite trivial to mount a >50% attack. If you own >50% of the hashrate, you own the network.

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While it may be trivial in implementation, its unrealistic due to the cost.

>In reality, the Bitcoin network has proven resilient enough to withstand a 51% attack over the years. In fact, due to the size of the Bitcoin network and the extent to which hash power is decentralized, along with the cost of mining equipment, it’s prohibitively expensive to attack Bitcoin. We estimate it would cost over $13 billion

https://learn.eqonex.com/news/what-51-attack-and-how-much-wo...

> We estimate it would cost over $13 billion

So basically it's less than what the U.S. Federal Government spends in one day (FY2021 spending totalled $6.83tn). Unrealistic.

That's $13 billion for the hardware, and $1 million per day in electricity assuming a cost of $0.01/kWh

$13 billion is a drop in the bucket for governments. The have been passing Trillion dollar bills for some time.

I doubt it would work in practice. If an actor repeatedly used ASICs to run a 51% attack, it wouldn’t take long for the community to switch hashing algorithm and render all that hardware useless.

How is "the community" going to switch when "the community" includes the 51%?

Everyone in the community who isn’t the 51% attacker would want to switch because a crypto that is vulnerable in this way has little value.

You have to continue executing the 51% attack forever, or else when you stop, the network goes back to normal. And about the worst thing you can do during such an attack is prevent transactions from confirming. You can't unilaterally rewrite the ledger, you can't steal money from people. So saying you "own the network" while executing such an attack is... pretty dumb.

> And about the worst thing you can do during such an attack is prevent transactions from confirming.

You can also double, triple or quadripule spend bitcoins and have those transactions confirm.

Yes, they’ll get marked as double spends, along with everything down that chain, but that’ll only happen once the network goes back to normal, and it would absolutely wreak havoc.

So no, it’s not just “all you can do is a denial of service”.

if someone "mounts" a 50% attack and is successful, do you think the rest of the world will simply accept their "attack"? bitcoin was forked into bitcoin cash once, why cant it happen again?

The bitcoin cash fork is incomparable, because it wasn't done because Bitcoin itself was under attack.

It doesn't even matter if there'd be a fork. It would be a significant disruption at the very least.

By what mechanism would they not accept? Sure you can leave and create a new network, as much as you can choose one of the many other cryptos already out there.

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