As more governments consider deploying Bitcoin reserves, the chance of attacks from Nation-state level cyber actors will keep increasing

For example, if the US introduces a large Bitcoin reserve, China may want to attack Bitcoin not just for profit, but simply to make the US look weak. The cost of the attack would be far smaller than the damage caused by the attack.

Bitcoin cannot defend against such a large-scale 51% attack if China spends $15-25B over the period of 5 years redirecting its massive manufacturing force to outbuild the rest of the world in mining supply. They can also buy up mining rigs from mining companies going out of business and from other companies over the period of many years. The longer they wait, the smaller Bitcoin's security budget will be relative to the amount of damage that can be caused due to the block subsidy halvings. The longer they wait, the easier it will be to cause more damage.

The point of a nation-state attack is to undermine confidence in Bitcoin by severely disrupt block production and causing a severe price crash. By simply spending as little as $20B in manufacturing resources, they could cause 100x of damage at $2T. This would make any competing nations holding Bitcoin reserves look weak and possibly experience citizen unrest.

There are many cost-efficient methods of disrupting block production

• Continuously mine empty blocks or blocks with useless spam transactions. This is still very profitable since the block subsidy is currently ~98% of the block reward. Transactions fees are negligible. The energy cost is covered.
• Only allow for extremely high priority fees to the point where no one wants to use the network except for desperate whales looking to fire-sell. The attacker can manipulate a market crash.
• Engage in selfish mining to lock out other mining pools and make more profit. Any attacker with 60% of the total mining power could reorg the blockchain and take 100% of mining rewards. That would increase their revenue by ~70% and increase their profits by much, much more.
• Withhold blocks: An attacker doesn't have to constantly produce blocks. They could slow down their block production, using withholding attack strategies to only broadcast blocks whenever a competing miner gets a block in. This would reduce the cost of attack as more miners drop out due to unprofitability.
• Keep reorging the blockchain and cause chaos. Many exchanges would shut down deposits and withdrawals.
• Threaten to double-spend across wrapped Bitcoin bridges or restaking side chains. Exchanges would not know how to react, and they would likely shut down trading.

There isn't an easy way to prevent such an attack

• If the Bitcoin community tries to fork without changing Bitcoin's consensus protocol, the attacker would just follow them to the new chain and continue attacking.
• If Bitcoin changes to a new mining protocol, then that would piss off all existing miners, reset its security, and undermine confidence in Bitcoin
• The Bitcoin community could decide to switch to a more secure protocol like PoS that protects against such attacks, but it could take a year of development and testing. Ethereum took 5 years. Bitcoin would need to start yesterday.

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What are your thoughts on how to protect Bitcoin from nation-state level threat actors?

51% attacks can totally be profitable.

It could just be normal mining where they produce empty blocks, or censor transactions of specific entities. They can get block rewards while still causing enough chaos to persuade others to switch to their side.

If a 51% attacker produces blocks normally, but reorgs 25% of its competitor's blocks, eventually its competitors will give up and stop mining. With fewer competitors, its work becomes easier and cheaper. Even more profit for them.

If the 51% attacker uses withholding attacks and selfish mining strategies, they could increase their profit even more. It's extremely profitable for 51% attackers.

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No imagine that Bitcoin's security budget drops to the point where over 50% of miners are no longer profitable, and they threaten to fork and continually attack Bitcoin until Bitcoin adds tail emissions. If a blockchain war breaks out, those 50%+ miners are going to win every time. Other miners would be forced to join them or else their blocks would get reorged.

If a CEX doesn't play friendly with the miners, the miners would censor their transactions. If the CEXs and nodes jump to a new blockchain, the attackers can jump too just to harass them. If the CEXs switch mining algorithms while still staying on PoW, they'd be starting from scratch.

The biggest problem is that as Bitcoin grows and the halvings continue, the ratio between the security budget to total value being protected trends downward over time. It becomes more and more profitable to attack Bitcoin or to execute minor harassment attacks to lower Bitcoin efficiency that can be done at 10% of the total hash rate (like censoring exchange transactions or producing empty blocks).

If the security budget no longer enough to sustain miners because transactions fees aren't high enough, the miners may choose to fork the chain to get rid of the supply cap so that they can remain profitable.

If this happens, the split chain would have all the largest miners, who could attack the 21M supply-cap at any time.

There's really nothing the 21M supply-cap chain can do to prevent a 51% attack without making Bitcoin's security even worse. They can't change their mining protocol without cause all miners to abandon the change.

I suppose they could switch to Proof of Stake like Ethereum, but the community doesn't want to discuss that possibility. Getting rid of the supply cap is the easiest solution to fixing Bitcoin's long-term problems.

I agree with the title, but I don't agree with why no one understands the 51% attack.

Too many people think that the method of 51% attacks is detectable while it's in progress because of how it's described in the Bitcoin whitepaper.

The actual method that nearly all successful 51% attacks on PoW networks have occurred is via withholding attacks, which are undetectable until the moment they execute.

One moment the blockchain is safe; the next second, 50 blocks are reorged all at once and it takes a whole day for honest miners to fight back, assuming they can even muster the mining power to do so.

Bitcoin has almost zero utility besides Store of Value and for most basic Bitcoin investors, that's good enough. At some point, a subset of those investors will get bored of Bitcoin and start venturing into altcoins.

Most will invest in altcoins but never actually use it for utility. But for those who actually care about technology and focus on utility will realize that Bitcoin really doesn't do anything unlike many altcoins.

I suspect investors who only care about profit will mainly stick with Bitcoin because it's a Store of Value and doesn't need to have any other utility. But those who use technology will migrate to altcoins.

That does not sound "simple" at all.

Antoine Riard is a senior Lightning dev, not just some junior dev.

Higher time_lock_delta leads to longer time for locked funds. That's a tradeoff.

Rebroadcasting with higher fees: Also known as "defensive fee mitigation". I suppose that's doable to keeping spamming the mempool dozens of times until the attacker gives up. Would be a simple client update, but it introduces additional spam and client complexity.

I'm going to wait until the experienced Lightning devs test this attack and report back the costs of attacking and defending. This is beyond my level of understanding.

It sounds like they're going to look for a sustainable fix, but it'll take several months of testing and implementation. In the meantime, I would refrain from keeping high value on Lightning, like everyone should've been doing from the start.

This seems very serious, at least for those with high-value channels.

I'd like to see some cost-analysis for this kind of attack. What's the cost of running the attack, and at what point does the attack become profitable under different scenarios:

1. victim does not detect the attack
1. victim is not using automation and defends against it manually and slowly

Both Peter and Paul were flawed followers of Jesus with their own self interests, so I think this is a pretty good analogy.

Let's assume Satoshi is Bitcoin Jesus.

Michael Saylor has his self interests and goals to spread Bitcoin adoption, regardless of whether his teachings align with Satoshi's. Similarly the Apostle Paul is the founder of Christianity, but his Christianity is noticeably different than Jesus's teachings. https://doctrine.org/jesus-vs-paul has a good summary of that.

Peter was mainly a follower of Jesus, but he was often skeptical of Jesus and denied Jesus 3 times right when Jesus needed him most.

There is no central authority for Bitcoin.

That's just one front-end. You're free to build your own node and keep everything uncensored as long as you don't care about operating illegally within your legal jurisdiction. Most websites like this one will have a reporting tool for removing illegal material. It's completely impractical not to have one unless you live in one of the few countries that allow any media content.

The blockchain as a whole operates without jurisdiction, but not individual node operators.

If you want to show Ordinal inscriptions, then do it. If you want to prune the witness signatures, then do it. That's the beauty of being able to choose how to run your node.

I checked it out. Where are the "disgusting" pictures? This is completely safe to show my mom and grandma.

I went through the first 3000 pictures (website is really slow for browsing). It's just literal wholesome family photos. Half of the pictures are family photos. The other half are boring vacation photos and food photos. They're just using it like a really boring Instagram or Facebook album.

If there were "disgusting" photos as you suggested, they've been reported and cleaned up a long time ago.