user131245: I was reading this question:
What can an attacker with 51% of hash power do?
According to that, the 3 "powers" obtained through controlling 51% or more would be:

Reverse transactions that he sends while he's in control
Prevent some or all transactions from gaining any confirmations
Prevent some or all other generators from getting any generations

These look a lot to me like centralized currency, minus the creation part, which can probably be worked around through non-blockchain means, anyway.
I think that a state level actor could definitely achieve this, but in this question:
What are some potential scenarios that a state actor can harm bitcoin if they control more than 51% of the hashing power?
Someone replies that it's not possible:

A 51% attack on Bitcoin may be theoretically possible, but it is definitely not feasible. Andreas Antonopoulos addressed this question and answers it better than I could. Here's a video of this Q&A: https://youtu.be/yWTQgmCuiCw?t=8

To me the answer seems quite arrogant (a state level entity investing billions in a covert operations and not involving black ops à la https://xkcd.com/538/ is just silly).
So my questions would be:

assuming not a purely financial gain (this would be about control, ergo politics)
what could prevent such an attack (especially if pin-point targeted violence from the attacking state level actor is an option)
and how can Bitcoin protect itself (Andreas Antonopoulos says that the attacker would be kicked out... how would that happen in practice?), assuming there are defense mechanisms possible?


user26481: It can be argued that most aspects of bitcoin network like mining, wallets, exchanges are already controlled by centralized actors. US mining operations and big companies like Coinbase / Blockchain.com have disproportionately large influence over bitcoin.
The important distinction here is that it may not be in the best economic interest of such centralized actors to attack the network or take overt control of the network. Here are few examples:
51% Mining attack

A double spend can be done by reversing bitcoin spent on exchange for money gain. However, if this is done consistently exchanges can spot this and increase number of confirmations to 6 or more which is very difficult to attack even with 51% hash rate control. Also network could hard fork reversing the double spend
Empty blocks can be mined effectively DDOSing the network. This could lead to a price fall which could be leveraged by shorting bitcoin

In both the above cases you are mining the block of a network which you are attacking. So the price of bitcoin you mined also falls down negatively effecting you. You could just get more richer by just mining bitcoin and selling it at higher price by working in favor of the network
Social and Financial Control
Governments can exercise social and financial and regulatory measures that may lead to soft or hard destruction. Some of these can be:

Covert multi-government effort conduct several propaganda campaigns to sway public opinion that the Bitcoin is either a massive scam or somehow bad
Mandating onchain KYC / taxation of each transaction
Financial institutions dump large amount of bitcoin effectively reducing price and creating panic
Making it illegal to hold bitcoin and other legal measures

While these may work to dissuade mainstream user, other forks of bitcoin will be spawned. Users will switch to such forks / privacy coins that maybe more difficult to track. Flip side is government may get even less information of crypto economic activity than what is currently getting

So in summary, lots of activity in bitcoin maybe in control of centralized actors. However, it would be in the best economic interest of such state actors to covertly / indirectly control it instead of attacking the network

131245: <p>I was reading this question:</p>
<p><a href="https://bitcoin.stackexchange.com/questions/658/what-can-an-attacker-with-51-of-hash-power-do">What can an attacker with 51% of hash power do?</a></p>
<p>According to that, the 3 &quot;powers&quot; obtained through controlling 51% or more would be:</p>
<blockquote>
<p>Reverse transactions that he sends while he's in control</p>
<p>Prevent some or all transactions from gaining any confirmations</p>
<p>Prevent some or all other generators from getting any generations</p>
</blockquote>
<p>These look a lot to me like centralized currency, minus the creation part, which can probably be worked around through non-blockchain means, anyway.</p>
<p>I think that a state level actor could definitely achieve this, but in this question:</p>
<p><a href="https://bitcoin.stackexchange.com/questions/92324/what-are-some-potential-scenarios-that-a-state-actor-can-harm-bitcoin-if-they-co">What are some potential scenarios that a state actor can harm bitcoin if they control more than 51% of the hashing power?</a></p>
<p>Someone replies that it's not possible:</p>
<blockquote>
<p>A 51% attack on Bitcoin may be theoretically possible, but it is definitely not feasible. Andreas Antonopoulos addressed this question and answers it better than I could. Here's a video of this Q&amp;A: <a href="https://youtu.be/yWTQgmCuiCw?t=8" rel="nofollow noreferrer">https://youtu.be/yWTQgmCuiCw?t=8</a></p>
</blockquote>
<p>To me the answer seems quite arrogant (a state level entity investing billions in a covert operations and not involving black ops à la <a href="https://xkcd.com/538/" rel="nofollow noreferrer">https://xkcd.com/538/</a> is just silly).</p>
<p>So my questions would be:</p>
<ul>
<li>assuming not a purely financial gain (this would be about control, ergo politics)</li>
<li>what could prevent such an attack (especially if pin-point targeted violence from the attacking state level actor is an option)</li>
<li>and how can Bitcoin protect itself (Andreas Antonopoulos says that the attacker would be kicked out... how would that happen in practice?), assuming there are defense mechanisms possible?</li>
</ul>
 26481: <p>It can be argued that most aspects of bitcoin network like mining, wallets, exchanges are <a href="https://blog.blockonomics.co/why-bitcoin-is-becoming-centralized-41f62cc15e91" rel="nofollow noreferrer">already controlled by centralized actors</a>. <a href="https://ichef.bbci.co.uk/news/976/cpsprodpb/14F6F/production/_122617858_optimised-bitcoin_hashrate-nc.png" rel="nofollow noreferrer">US mining operations</a> and big companies like Coinbase / Blockchain.com have disproportionately large influence over bitcoin.</p>
<p>The important distinction here is that it may not be in the best economic interest of such centralized actors to attack the network or take overt control of the network. Here are few examples:</p>
<p><strong>51% Mining attack</strong></p>
<ul>
<li>A double spend can be done by reversing bitcoin spent on exchange for money gain. However, if this is done consistently exchanges can spot this and increase number of confirmations to 6 or more which is very difficult to attack even with 51% hash rate control. Also network could hard fork reversing the double spend</li>
<li>Empty blocks can be mined effectively DDOSing the network. This could lead to a price fall which could be leveraged by shorting bitcoin</li>
</ul>
<p>In both the above cases you are mining the block of a network which you are attacking. So the price of bitcoin you mined also falls down negatively effecting you. You could just get more richer by just mining bitcoin and selling it at higher price by working in favor of the network</p>
<p><strong>Social and Financial Control</strong></p>
<p>Governments can exercise social and financial and regulatory measures that may lead to <a href="https://bitcoin.stackexchange.com/questions/366/what-methods-could-a-government-use-to-shutdown-bitcoin">soft or hard destruction</a>. Some of these can be:</p>
<ul>
<li>Covert multi-government effort conduct several propaganda campaigns to sway public opinion that the Bitcoin is either a massive scam or somehow bad</li>
<li>Mandating onchain KYC / taxation of each transaction</li>
<li>Financial institutions dump large amount of bitcoin effectively reducing price and creating panic</li>
<li>Making it illegal to hold bitcoin and other legal measures</li>
</ul>
<p>While these may work to dissuade mainstream user, other forks of bitcoin will be spawned. Users will switch to such forks / privacy coins that maybe more difficult to track. Flip side is government may get even less information of crypto economic activity than what is currently getting</p>
<hr />
<p>So in summary, lots of activity in bitcoin maybe in control of centralized actors. However, it would be in the best economic interest of such state actors to covertly / indirectly control it instead of attacking the network</p>
