Comment by nullc | Hacker News Reader

Comment by nullc | Hacker News Reader

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My (Greg Maxwell, a developer of the Bitcoin reference client) preliminary look at it is here: https://bitcointalk.org/index.php?topic=324413.msg3476697#ms...

In short, the new thing here is the assumption that the attacker uses a network positional advantage to eliminate the loss associated with delaying blocks.

I am not fond of their proposed solution, since it creates a size advantage for large miners (of sizes which have already existed) in all cases, even without the network attack.

I'd rather initially focus on strengthening the network against the formation of the positional advantage in the short term. (There is already some belief that there is extensive peering between miners making the attack ineffective, but its impossible to know if its adequate, so there is no harm in in strengthening that some.)

This is not right. We show that, even with no positional advantage in the network (i.e. gamma=0), the attacker can make more than its fair share.

If you're still reading: wouldn't having a gamma value significantly larger than 0 mean that for each miner, it has more malicious peers than honest ones?

For example, let's assume a "levels" topology, where mined blocks propagate in discrete turns from the miner to its peers, then to their peers, etc. If there are more honest peers on the first level, wouldn't the "honest" block (X in the paper) propagate faster than the pool block, P?

BTW, I found the paper absolutely fascinating regardless of this relatively minor issue. As you said, even with gamma=0, an attack is feasible.

Are near-block-headers a likely improvement or would they make this vulnerability worse?

Nope, I was wrong and misunderstood the attack. (like most people) They would likely make the attack easier to accomplish, rather than less.

Unfortunately there's very little we can do to defeat this attack, other than have miners use strategies that aren't strictly economically rational in the short term for them. In practice a sufficient amount of miners may be willing to do this, but if they aren't we're going to need better countermeasures than that.

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