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by Lerc 359 days ago
So the two questions that I cannot see answered there.

How much does the security budget need to be?

When is it projected to drop below that?

The closest they come to addressing that seems to be a quote saying "We might have only two halvings left before this becomes a serious issue."

So 8 years-ish?

The original intention was to fund the network entirely off fees eventually. I don't think there was a stated expectation of block size, but it was intended to be made larger at some point.

Before coming up with specific solutions to the cost of securing the network I would think that evaluating what the acceptable range of cost/security should be would be the first starting point.

I feel they also neglect a realistic evaluation of the likelihood of a 51% attack. As soon as someone interferes with the network by 51% attack, everybody knows that it has happened. What countermeasures might be deployed?

While a miner confirming a block is like a rubber stamp from an auditor, there is nothing to stop other people from checking their work. If there are shenanigans they can be spotted, if a genuine 51% attack were to happen people would be highly motivated to counter it. That may involve bringing more compute to the network, or even changing the protocol. Ultimately the network is decided by the consensus of the users. Accepting signed blocks is the consensus. Because of the scale required to do a 51% attack on BitCoin it would almost certainly be detectable who was doing it. Under an attack people would be prepared to swiftly agree to some rule to exclude the attacker, the alternative is just two severe. You could think of it as a fork or you could think of the attackers version as the fork. You could have anything from, 'Today we stop accepting blocks from that pool over there', to 'From now until this mess is resolved, Kate confirms all blocks with her private key, We trust Kate, she's nice' The mitigation could be prosaic or fantastic, it doesn't matter, the thing that people agree upon will be the new chain. A fallback proof of work algorithm that requires more generalised hardware would work well. In case of attack, switch back to GPUs and a lower hash rate on a newer algorithm. ASICs become redundant and the network redistributes to whoever is supplying the GPUs. Then to do a 51% attack the attacker must not only have enough to 51% the ASIC hash rate, but have in reserve more GPUs than the rest of the world can bring to bear at short notice to 51% the fallback method.

4 comments

>How much does the security budget need to be?

I don't know but I expect it to be proportional to market cap, not getting cut in half forever.

>The original intention was to fund the network entirely off fees eventually.

I think this was a half-baked idea from satoshi. My theory is that the bitcoin distribution was chosen to avoid having to decide on any "arbitrary" emission schedule. Bitcoin basically acts an experiment to determine what level of coinbase reward is safe, through bisection.

>if a genuine 51% attack were to happen people would be highly motivated to counter it. That may involve bringing more compute to the network, or even changing the protocol.

Who? Just bitcoin users in general? There is no group that stands to gain, it's sort of a tragedy of the commons situation.

Bitcoin's security is tied to ASIC hardware. You can't just spin up a couple desktops at home to protect the network anymore.

>A fallback proof of work algorithm that requires more generalised hardware would work well.

I think monero already does this. Look up "RandomX" it is amazing to read about. But the problem is that these CPU-mined coins are even easier to attack because you can easily rent hardware or use a botnet to do a 51% attack. Whereas with bitcoin you need to buy a bunch of ASICs which would be devalued by such an attack.

>Ultimately the network is decided by the consensus of the users. Accepting signed blocks is the consensus.

I was going to write a long response to this, but in a nutshell classical consensus and PoS sucks.

> How much does the security budget need to be?

There's the famous paper "The Economic Limits of Bitcoin and the Blockchain" [0, 1] answering this question. Bottom line: huge.

> Nakamoto’s novel form of trust faces serious economic limits. It is unusually expensive in absolute terms relative to the stakes involved, and its expense scales linearly with the stakes involved. [...] if permissionless consensus in its pure form were to become a more important part of the global economic and financial system than it has been to date, then the costs of securing the trust would become preposterous — more than all of global GDP in some scenarios.

David Rosenthal has good introductory posts on this [2] in his excellent blog.

[0] Original 2018 version: https://www.nber.org/papers/w24717

[1] Updated 2024 version [pdf]: https://socialsciences.uchicago.edu/sites/default/files/2024...

[2] https://blog.dshr.org/2025/05/who-is-mining-bitcoin.html

https://blog.dshr.org/2018/06/cryptocurrencies-have-limits.h...

https://blog.dshr.org/2019/02/the-economics-of-bitcoin-trans...

https://blog.dshr.org/2024/05/fee-only-bitcoin.html

The big issue is the fork and fixing it represents a decision about who has and hasn't gotten paid so the fork is quite sticky for those who's transactions do not appear on the post attack branch to want to stick the the attacked branch. This was relatively easy when they did it in the early days of ETH after the DAO hack but AFAIK there's no on chain mechanism for a similar hard fork to happen to BTC. Even in ETH I'd be surprised if a similar response happened to a similar level of attack, voting power on EIPs was significantly more concentrated back in 2016.

Any way you slice it there's still a centralization of power of when to activate any of these defense mechanisms.

How much really has to be measured with respect to a motivated attacker. If no one wants to attack it, it could stay low for a long time. The ideal answer would be to keep the hash rate as high as possible for as long as possible. With the appreciation of the asset, people would think the risk of an attack is growing higher but an attacker can only do so much with 51%.

They can either double spend by reversing the chain (in which case they’d have to accumulate enough bitcoin for to make it worthwhile in the first place) or they can mine empty blocks and prevent any transactions from being processed.