alt Hacker NewsPart of this post addresses the economics of creating a 6 block re-org. This makes sense as 6-confimations is the standard for Bitcoin finality today.
However, as Bitcoin's security inevitably weakens over the coming years due to diminishing miner rewards (denominated in BTC), I believe this "6-confimation" acceptance policy will change to include not only the number of confirmations, but the timing of those confirmations as well. Consider a scenario where an exchange deciding whether a tx with 6-confirmations that took 4 hours to arrive (this happens occasionally) is safe to consider finalized/settled. Even though 6-confimations may be considered safe by today's acceptance policies, this tx would still have a high probability of double spend due to the assumed 4-hour long wait for the 6 confirmations (as the attacker would have 4 hours to produce 7 blocks instead of the normal/expected 1 hour). Instead of ignoring block interarrival timing, it may make sense to include block timing as part of an acceptance policy.
So, going forward Bitcoin acceptance policies may change from today's 6-confirmation standard to something more complicated that involves the amount of time those blocks took to arrive. This would significantly enhance Bitcoin's double spending resistance without adding/altering any code and may give the network a much needed security boost in the coming years to prevent the attack discussed in the post.
Replies
"Bitcoin's security inevitably weakens over the coming years due to diminishing miner rewards (denominated in BTC)"
That's incorrect. Security scales with USD-denominated rewards, not BTC-denominated. And there are 16 years of real-world data showing they have been generally increasing, so a healthy sign that the Bitcoin experiment is working:
https://newhedge.io/bitcoin/block-reward-per-block
And not only that, but rewards are still expected to stabilize even when measured in BTC (thereby not relying on an increase of BTC's price) as they are progressively composed more and more of tx fees instead of newly mined BTC.
It's puzzling to me why some still don't understand the systemic incentives that make all this work as it has for 16 years and counting...
> This would significantly enhance Bitcoin's double spending resistance without adding/altering any code
I would have expected such security rules are part of the miner code, no? Don't they need to consider rules related to the comparative security level of a chain when decided which chain to follow when multiple exist?
> However, as Bitcoin's security inevitably weakens over the coming years due to diminishing miner rewards (denominated in BTC),
Says you, without a hint of a rationale backing your argument.
It seems to me that the historical hashing rate curve tells a different story.
And block rewards have been diminishing regularly (and very predictably) pretty much since day one.
you can accept bitcoin at any confirmation you want, it isn't a policy
If the attacker is waiting for a lucky event to occur (finding more blocks than others while having less than 51% of the mining power) it means that they are constantly wasting mining time. That in itself is a huge cost (operational cost and block rewards thrown away), but it also means that they can't predict when it will happen. A double spend attack must be planned in advance because the first transaction must occur at the beginning of the attack. I'm not sure how they could constantly try double spends without risking losing the money each time the attack doesn't happen.
I don't see how it could be profitable. If it can't be profitable, then the risk of someone doing it is pretty low. If they already have the necessary hardware, they'd be much better off mining.