Is 51% attack a double-spending threat to bitcoin?

[amishmanish]

Full nodes have no power to mitigate the real attacks a hypothetical 51% collided pools can carry out, no matter how many of them are present:

Apart from the 51% attack mitigation, I think you are ignoring the fact that full nodes run by normal users are essentially what make bitcoin collapse/ takeover resistant. A system comprised only of miners (if there are no non-mining full nodes) or entities with the ability to run specialized hardware (for chains with large blocks and enormous throughput requirements) can never be as takeover resistant due to centralized points of failures.

A system with millions of user maintained full nodes will just trudge along, no matter what. That is a worthy feature to ensure robustness in the face of calamity (natural or man-made).

[aliashraf]

Full nodes have no power to mitigate the real attacks a hypothetical 51% collided pools can carry out, no matter how many of them are present:

.. I think you are ignoring the fact that full nodes run by normal users are essentially what make bitcoin collapse/ takeover resistant.

It is not a fact, just a false assertion. Bitcoin is resistant to collapse/takeover because of the game theory behind the scene.

There is no party named "full nodes coalition" or something, established to keep bitcoin safe and secure. As a single user, I don't care about anything other than my own security and I won't pay a penny to keep you or "the community" secure.

[amishmanish]

Full nodes have no power to mitigate the real attacks a hypothetical 51% collided pools can carry out, no matter how many of them are present:

.. I think you are ignoring the fact that full nodes run by normal users are essentially what make bitcoin collapse/ takeover resistant.

It is not a fact, just a false assertion. Bitcoin is resistant to collapse/takeover because of the game theory behind the scene.

There is no party named "full nodes coalition" or something, established to keep bitcoin safe and secure. As a single user, I don't care about anything other than my own security and I won't pay a penny to keep you or "the community" secure.

If there are no full nodes, then won't the network stop existing in case of a takeover of centralized pools/ miners?  On the other hand, user run full nodes with a geographic diversification the world over, serviced by different ISPs etc. can keep running under even such conditions. Its a worst case scenario which needs full nodes plus home miners.

That is also the original peer-to-peer network and it can survive no matter what; but only if the block chain rules continue to allow full nodes to run.

[aliashraf]

Full nodes have no power to mitigate the real attacks a hypothetical 51% collided pools can carry out, no matter how many of them are present:

.. I think you are ignoring the fact that full nodes run by normal users are essentially what make bitcoin collapse/ takeover resistant.

It is not a fact, just a false assertion. Bitcoin is resistant to collapse/takeover because of the game theory behind the scene.

There is no party named "full nodes coalition" or something, established to keep bitcoin safe and secure. As a single user, I don't care about anything other than my own security and I won't pay a penny to keep you or "the community" secure.

If there are no full nodes, then won't the network stop existing in case of a takeover of centralized pools/ miners?  On the other hand, user run full nodes with a geographic diversification the world over, serviced by different ISPs etc. can keep running under even such conditions. Its a worst case scenario which needs full nodes plus home miners.

That is also the original peer-to-peer network and it can survive no matter what; but only if the block chain rules continue to allow full nodes to run.

Home miners plus full nodes is not a backup plan for D-day, it is the original plan which failed in 2011-2012 after pooling pressure falw showed its power and pools started to dominate the mining scene of bitcoin. Since then we are running plan B: Centralized mining, no home miner, less full nodes AND game theory.

[Wind_FURY]

even if you are right about the game theory, why give miners that opportunity?

Fair question. Before proceeding to it let's have a comparison between the role of game theory and full nodes (supposedly millions of them) in securing bitcoin:

Full nodes have no power to mitigate the real attacks a hypothetical 51% collided pools can carry out, no matter how many of them are present:

- Short-range chain rewrite attacks are not detectable by full nodes, they just bend the knee to the more difficult chain, forget about resisting against such attacks.

- Long-range attacks are the same as it is just a relative concept.

- Full nodes can't resist censorship/blacklisting attacks against peoples/institutions/nations.

- Full nodes can resist against protocol breach and most importantly double-spending/illegal-inflation attempts very well.

If the transactions, and blocks are not valid/doesn't follow the consensus rules. Those transactions/blocks won't be relayed by full nodes. The energy spent will be wasted. That's the game theory.

Full nodes have no power to mitigate the real attacks a hypothetical 51% collided pools can carry out, no matter how many of them are present:

.. I think you are ignoring the fact that full nodes run by normal users are essentially what make bitcoin collapse/ takeover resistant.

It is not a fact, just a false assertion. Bitcoin is resistant to collapse/takeover because of the game theory behind the scene.

There is no party named "full nodes coalition" or something, established to keep bitcoin safe and secure. As a single user, I don't care about anything other than my own security and I won't pay a penny to keep you or "the community" secure.

If there are no full nodes, then won't the network stop existing in case of a takeover of centralized pools/ miners?  On the other hand, user run full nodes with a geographic diversification the world over, serviced by different ISPs etc. can keep running under even such conditions. Its a worst case scenario which needs full nodes plus home miners.

That is also the original peer-to-peer network and it can survive no matter what; but only if the block chain rules continue to allow full nodes to run.

Home miners plus full nodes is not a backup plan for D-day, it is the original plan which failed in 2011-2012 after pooling pressure falw showed its power and pools started to dominate the mining scene of bitcoin. Since then we are running plan B: Centralized mining, no home miner, less full nodes AND game theory.

Then the more we are required to verify things for ourselves.

Plus if you truly believe that your one node network will be adversarially safe from a collusion by a cartel of miners, because "game-theory", and that users shouldn't run nodes, then what are we in Bitcoin for? Remove POW too, and make it cheaper.

[Railai]

I had last month a 0.25 btc double spent while having a trade. It still can be done, be aware!

[Wind_FURY]

I had last month a 0.25 btc double spent while having a trade. It still can be done, be aware!

Hahaha.

Newbies, ask him at what cost to the miner, and if it was worth double-spending the 0.25 Bitcoins, with the full nodes validating EVERYTHING in the network.

[aliashraf]

If the transactions, and blocks are not valid/doesn't follow the consensus rules. Those transactions/blocks won't be relayed by full nodes. The energy spent will be wasted. That's the game theory.

Nope.

The incentive may help encourage nodes to stay honest.  If a greedy attacker is able to assemble more CPU power than all the honest nodes, he would have to choose between using it to defraud people by stealing back his payments, or using it to generate new coins.  He ought to find it more profitable to play by the rules, such rules that favour him with more new coins than everyone else combined, than to undermine the system and the validity of his own wealth.

That's the game theory.

Plus if you truly believe that your one node network will be adversarially safe from a collusion by a cartel of miners, because "game-theory", and that users shouldn't run nodes, then what are we in Bitcoin for? Remove POW too, and make it cheaper.

Firstly, I don't say users shouldn't run nodes, on the contrary I'm thinking of and advocating for mobile full nodes: every user one full node! I'm saying it is not helping bitcoin security to have a zillion full nodes, it is just about every single user to avoid being the one whose name is supposed to go first to the news. Full nodes do not form an institution to keep bitcoin safe! I'm just wondering: How people have managed to deduct such a stupid argument?

Secondly, PoW is essential for the game theory behind bitcoin and it is why PoS is shit.

[Wind_FURY]

If the transactions, and blocks are not valid/doesn't follow the consensus rules. Those transactions/blocks won't be relayed by full nodes. The energy spent will be wasted. That's the game theory.

Nope.

The incentive may help encourage nodes to stay honest.  If a greedy attacker is able to assemble more CPU power than all the honest nodes, he would have to choose between using it to defraud people by stealing back his payments, or using it to generate new coins.  He ought to find it more profitable to play by the rules, such rules that favour him with more new coins than everyone else combined, than to undermine the system and the validity of his own wealth.

That's the game theory.

That WAS the game theory BEFORE the cartelization of mining. Satoshi did not fully know future. How could the community express themselves if their ability to run a full node was taken away?

Full nodes create demand for blocks for the miners to supply, and relay them only if valid/follows consensus rules.

Plus if you truly believe that your one node network will be adversarially safe from a collusion by a cartel of miners, because "game-theory", and that users shouldn't run nodes, then what are we in Bitcoin for? Remove POW too, and make it cheaper.

Firstly, I don't say users shouldn't run nodes, on the contrary I'm thinking of and advocating for mobile full nodes: every user one full node! I'm saying it is not helping bitcoin security to have a zillion full nodes, it is just about every single user to avoid being the one whose name is supposed to go first to the news. Full nodes do not form an institution to keep bitcoin safe! How people have managed to deduct such a stupid argument?

But full nodes do secure the network. Any block/transaction that isn't following the consensus rules, won't be relayed. Bitcoins is actually a network of validation.

Secondly, PoW is essential for the game theory behind bitcoin and it is why PoS is shit.

Not if the network is centralized towards the miners, and could collude to co-opt Bitcoin's development WITHOUT community consensus. Maybe they should remove POW, to remove costs. Haha.

[aliashraf]

The incentive may help encourage nodes to stay honest.  If a greedy attacker is able to assemble more CPU power than all the honest nodes, he would have to choose between using it to defraud people by stealing back his payments, or using it to generate new coins.  He ought to find it more profitable to play by the rules, such rules that favour him with more new coins than everyone else combined, than to undermine the system and the validity of his own wealth.

That's the game theory.

That WAS the game theory BEFORE the cartelization of mining. Satoshi did not fully know future. How could the community express themselves if their ability to run a full node was taken away?

Nope. That is Plan B: What if "a greedy attacker is able to assemble more CPU power than all the honest nodes"?
"The community" would come here, start a topic and warn about the shit, it gets viral and the attacker and his coins are doomed in a few hours. Full nodes aren't helpful in most attack scenarios anyway.

But full nodes do secure the network. Any block/transaction that isn't following the consensus rules, won't be relayed. Bitcoins is actually a network of validation.

Relaying blocks is not a big deal. Your argument is not qualified enough to be discussed here, sorry, blocks get relayed anyway, e.g by collided pools. Plus, full nodes are not able to detect mal-incentivized reorgs and censorship the most practical threats due to mining centralization.

[amishmanish]

For the purposes of the OP, I'd say it's likely you are correct in the assertion that it's mainly game theory keeping that part in check.  But that shouldn't in any way be interpreted to mean we don't still need a healthy node-count.

We are arguing on the basic premise that having a healthy full-node count is a desirable situation or not. Your argument is that full nodes are useless in terms of keeping miners in check because the game theory will keep the rational miners in check. Those of us who think that full nodes aren't completely useless say so because  of two reasons:

1. Bitcoin network is equally a network of users/ businesses running full nodes that validate and propagate well-formed transactions, which of course is the only thing they can watch out for and not double spends. (You said in reply to @Wind_Fury that block propagation is not an issue. Is it because in a hypothetical 'miner-collusion scenario' propagation will any way happen between their own full-nodes over relay networks like FIBRE ?)
2. Having this network of full nodes is the best way to remain vigilant. If we depend on, say, a few guardian nodes and then media to keep the game theory going then you are again dependent on centralized authorities as DooMad had been saying.

Keeping the ability to maintain and run full nodes should always remain a low-barrier activity not just because of fear of miner collusion/ attacks but because a lot of properties of bitcoin arise from it, namely decentralization and being your own bank, even in the D-day situations, even if media becomes dishonest, even if a concerted attack targets miners in some jurisdictions rendering the miners disconnected. If we just accept that all of this is paranoia and in reality, such attacks are not possible then of course there is no need for full nodes.
 

Home miners plus full nodes is not a backup plan for D-day, it is the original plan which failed in 2011-2012 after pooling pressure falw showed its power and pools started to dominate the mining scene of bitcoin. Since then we are running plan B: Centralized mining, no home miner, less full nodes AND game theory.

Thanks for the link to your topic on PoCW. It aims to solve the problem of pooling because i guess you do believe that centralized pools can coordinate and they reduce decentralization.(??) Yet, if miners are to be trusted and no full-nodes are needed then doesn't that create the same problem?? Huge mining farms can coordinate. Instead of debating about need of full-nodes, i will go and read about these proposed scaling solutions you think are being ignored due to the love of full-nodes..

[aliashraf]

For the purposes of the OP, I'd say it's likely you are correct in the assertion that it's mainly game theory keeping that part in check.  But that shouldn't in any way be interpreted to mean we don't still need a healthy node-count.

We are arguing on the basic premise that having a healthy full-node count is a desirable situation or not. Your argument is that full nodes are useless in terms of keeping miners in check because the game theory will keep the rational miners in check. Those of us who think that full nodes aren't completely useless say so because  of two reasons:

1. Bitcoin network is equally a network of users/ businesses running full nodes that validate and propagate well-formed transactions, which of course is the only thing they can watch out for and not double spends. (You said in reply to @Wind_Fury that block propagation is not an issue. Is it because in a hypothetical 'miner-collusion scenario' propagation will any way happen between their own full-nodes over relay networks like FIBRE ?)
2. Having this network of full nodes is the best way to remain vigilant. If we depend on, say, a few guardian nodes and then media to keep the game theory going then you are again dependent on centralized authorities as DooMad had been saying.

Keeping the ability to maintain and run full nodes should always remain a low-barrier activity not just because of fear of miner collusion/ attacks but because a lot of properties of bitcoin arise from it, namely decentralization and being your own bank, even in the D-day situations, even if media becomes dishonest, even if a concerted attack targets miners in some jurisdictions rendering the miners disconnected. If we just accept that all of this is paranoia and in reality, such attacks are not possible then of course there is no need for full nodes.
 

couples of hundreds
Home miners plus full nodes is not a backup plan for D-day, it is the original plan which failed in 2011-2012 after pooling pressure falw showed its power and pools started to dominate the mining scene of bitcoin. Since then we are running plan B: Centralized mining, no home miner, less full nodes AND game theory.

Thanks for the link to your topic on PoCW. It aims to solve the problem of pooling because i guess you do believe that centralized pools can coordinate and they reduce decentralization.(??) Yet, if miners are to be trusted and no full-nodes are needed then doesn't that create the same problem?? Huge mining farms can coordinate. Instead of debating about need of full-nodes, i will go and read about these proposed scaling solutions you think are being ignored due to the love of full-nodes..

I think there is a deep, deep, misunderstanding: Actually, I am the one who is in favor of having millions of full nodes and the guys like @DooMAD and @Wind_FURY are the ones who are against it, practically! 

How? Let's dive in:
There is a very efficient, secure way of running a bitcoin full node on commodity mobile devices very efficiently in economic mode, called UTXO commitment. According to this model miners would have to commit to the UTXO (state of the bitcoin machine) by somehow including its hash in their blocks and a light full-node could besides synchronizing headers like a usual SPV wallet continue to downloading the full state of the machine as of latest couples of hundreds of blocks and act like an ordinary pruned full node thereafter. Right?

For this to happen, you need a simple soft fork which is not getting support, why? Because people are paranoid about miners being susceptible to commit to bad UTXOs for say 500 blocks!

Are we clear? This full-node, full-node propaganda is totally fake and misleading. It is not a campaign in favor of empowering bitcoin users by giving them an opportunity to run a full node, it is just a trick to relying less and less on miners in a baseless and paranoid way: Who in the hell can imagine a scenario in which miners are colliding for 3-4 days to inject a few false UTXOS in bitcoin blockchain? A paranoid or a politician.

[Wind_FURY]

The incentive may help encourage nodes to stay honest.  If a greedy attacker is able to assemble more CPU power than all the honest nodes, he would have to choose between using it to defraud people by stealing back his payments, or using it to generate new coins.  He ought to find it more profitable to play by the rules, such rules that favour him with more new coins than everyone else combined, than to undermine the system and the validity of his own wealth.

That's the game theory.

That WAS the game theory BEFORE the cartelization of mining. Satoshi did not fully know future. How could the community express themselves if their ability to run a full node was taken away?

Nope. That is Plan B: What if "a greedy attacker is able to assemble more CPU power than all the honest nodes"?

"The community" would come here, start a topic and warn about the shit, it gets viral and the attacker and his coins are doomed in a few hours. Full nodes aren't helpful in most attack scenarios anyway.

The full nodes validates, that every transaction/block follow the consensus rules. If a miner mines an invalid block, it won't be relayed be the nodes.

But full nodes do secure the network. Any block/transaction that isn't following the consensus rules, won't be relayed. Bitcoins is actually a network of validation.

Relaying blocks is not a big deal. Your argument is not qualified enough to be discussed here, sorry, blocks get relayed anyway, e.g by collided pools.

I don't see how this part of your post is right. That is simply wrong, and I doubt you truly understand how the Bitcoin network works.

Plus, full nodes are not able to detect mal-incentivized reorgs and censorship the most practical threats due to mining centralization.

Then why haven't they tried it?

How? Let's dive in:

There is a very efficient, secure way of running a bitcoin full node on commodity mobile devices very efficiently in economic mode, called UTXO commitment. According to this model miners would have to commit to the UTXO (state of the bitcoin machine) by somehow including its hash in their blocks and a light full-node could besides synchronizing headers like a usual SPV wallet continue to downloading the full state of the machine as of latest couples of hundreds of blocks and act like an ordinary pruned full node thereafter. Right?

If "that" doesn't validate and relay transactions/blocks, then it's not doing anything for the network, and therefore not part of the network.

[aliashraf]

Relaying blocks is not a big deal. Your argument is not qualified enough to be discussed here, sorry, blocks get relayed anyway, e.g by collided pools.

I don't see how this part of your post is right. That is simply wrong, and I doubt you truly understand how the Bitcoin network works.

Blocks are relayed to any client, being a mining full node, a full node wallet, an SPV wallet, a blockchain explorer, ...) who connect to a pool/solo-miner and/or any full node that accepts inbound connections. What do you mean by accusing me of being ignorant about bitcoin relay network? It is not so complicated and I've been discussing it on many occasions in this forum.

Plus, full nodes are not able to detect mal-incentivized reorgs and censorship the most practical threats due to mining centralization.

Then why haven't they tried it?

You guess! It is not a rational move, simple game theory.

How? Let's dive in:

There is a very efficient, secure way of running a bitcoin full node on commodity mobile devices very efficiently in economic mode, called UTXO commitment. According to this model miners would have to commit to the UTXO (state of the bitcoin machine) by somehow including its hash in their blocks and a light full-node could besides synchronizing headers like a usual SPV wallet continue to downloading the full state of the machine as of latest couples of hundreds of blocks and act like an ordinary pruned full node thereafter. Right?

If "that" doesn't validate and relay transactions/blocks, then it's not doing anything for the network, and therefore not part of the network.

"That" is an ordinary bitcoin pruned full node and does everything an ordinary full node can do other than uploading the ancient history of blockchain for the current (stupid) bootstrap process.

[a.s.t.e.r.i.s.k]

aliashraf,

Your original question and discussion in your thread is a total mess. You are using very unclear terms, and you are bending Bitcoin terms in a way that shows that you do not understand Bitcoin's security model.

You don't understand what a "full node" is (as you confuse it with SPV), and you don't understand its role in the network.

It's a headache to read what you write as you appear to be ranting and make half-points all along the way.


Confusion..
Here is only one example of your confusions:

There is a very efficient, secure way of running a bitcoin full node on commodity mobile devices very efficiently in economic mode, called UTXO commitment.

Here is more confusion:

According to this model miners would have to commit to the UTXO (state of the bitcoin machine) by somehow including its hash in their blocks and a light full-node could besides synchronizing headers like a usual SPV wallet continue to downloading the full state of the machine as of latest couples of hundreds of blocks and act like an ordinary pruned full node thereafter. Right?

For this to happen, you need a simple soft fork which is not getting support, why? Because people are paranoid about miners being susceptible to commit to bad UTXOs for say 500 blocks!

Even more confusion:

Are we clear? This full-node, full-node propaganda is totally fake and misleading. It is not a campaign in favor of empowering bitcoin users by giving them an opportunity to run a full node, it is just a trick to relying less and less on miners in a baseless and paranoid way:

Even more confusion:

Who in the hell can imagine a scenario in which miners are colliding for 3-4 days to inject a few false UTXOS in bitcoin blockchain? A paranoid or a politician.

I started out reading your thread coming from a place of being willing to help and to clarify how Bitcoin works, but after reading your responses, I'm not convinced you are interested at all.


Bitcoin safe to double spend, based on fully validating nodes
Just to start somewhere, Bitcoin does solve the double spend problem. This is achieved by that participants run fully verifying nodes, and each such node enforce Bitcoin's consensus on every transaction of every block, and this will mean that in one node's view and perception, no double-spend ever occurs.

Miners are then free to mess up with blocks as much as they like, but they do so at their expense, so as long as the value of your transactions are insignificantly small compared to the Bitcoin miners' electricity expenses, you're safe - it's highly unlikely that someone will want to play appear-disappear reorg games with your 100USD transaction when it costs 10,000USD to mine a block.


UTXO commitments discussion
Regarding UTXO commitments, again you discuss these without understanding Bitcoin.

I'll share with you here that UTXO commitments are somehow similar to Ethereum 1's blocks' merkleized state snapshots.

What happened in the Ethereum community then was that, they fell for the temptation of validating blocks at all - when the Ethereum network is too busy, it will trig a feature that they call "fast forward", where a fully validating node will skipover one or more blocks, and thus simply blindly trusts the other nodes and the miners that they didn't forge anything. This is extremely risky and a viable attack vector for attacking their blockchain.

Further discussion of Bitcoin's security model, the definition of decentralization, and of that, here: https://hackernoon.com/the-ethereum-blockchain-size-has-exceeded-1tb-and-yes-its-an-issue-2b650b5f4f62


UTXO commitments infallible as you suggest is not correct
Your assertion that "UTXO commitments would always be valid because the miners are always attentive, correct and would never want to trick anyone" does not hold.

My take (which is a surprise somehow):
Unlike what is said ever and ever, one could put trust in miners as long as there is proof that:

• Miners are not inflating the supply illegally,
• The costs involved in defrauding him/her (personally) by re-org attacking the bllockchain are orders of magnitude higher than the assets he/she has put in stake.
  

Again, this reads confused, you need to be more specific and clear.


A 51% attack would not let through a double-spend
Last to respond to your question in the thread's title, "Is 51% attack a double-spending threat to Bitcoin?", I guess you have the answer already: It is not.


Asterisk

[amishmanish]

Are we clear? This full-node, full-node propaganda is totally fake and misleading. It is not a campaign in favor of empowering bitcoin users by giving them an opportunity to run a full node, it is just a trick to relying less and less on miners in a baseless and paranoid way: Who in the hell can imagine a scenario in which miners are colliding for 3-4 days to inject a few false UTXOS in bitcoin blockchain? A paranoid or a politician.

I think this is again pretty much a question of what you think bitcoin is. A lot of people out there think a lot of things about what bitcoin is and there are claims from con-marketeers about "Real Bitcoin" "True Vision" etc etc.  If you feel that we CAN trust miners, media can be believed to disseminate trustworthy information, full nodes are not needed etc etc. then there are plenty of other centralized scaling approaches out there.

If we take all these issues on privacy, trust on miners, media etc for granted then you are not in agreement with the privacy and security model of bitcoin made possible because of full nodes.

[aliashraf]

Asterisk,

Welcome back to the bitcoin discussion forum as a newbie, I was waiting for you and I hope you expect nothing less than full hiding here (just kidding  )

Meanwhile, please behave and do not make an embracement out of this brand new id too. I know who you are, and I understand it is a shame for the bitcoin community to watch an important figure being humiliated because of his own reckless manner of debating. I understand too, it is hard for you to get rid of your own malicious discourse. But come on, just give this fake id a shot and think out of the box if you may.
 
I see no confusion in what you have quoted from me. It is crystal clear: Your claim about full nodes playing such a crucial role in bitcoin is simply wrong and baseless. As I've extensively discussed up-thread, full nodes have nothing to do with the network security, they are just useful for the entities who own them as a single body to keep them somewhat more secure against some attacks that are not considered realistic anyway.

So, I skip the embracing confusion part of your post if you don't mind.

UTXO commitments discussion
Regarding UTXO commitments, again you discuss these without understanding Bitcoin.

I'll share with you here that UTXO commitments are somehow similar to Ethereum 1's blocks' merkleized state snapshots.

What happened in the Ethereum community then was that, they fell for the temptation of validating blocks at all - when the Ethereum network is too busy, it will trig a feature that they call "fast forward", where a fully validating node will skipover one or more blocks, and thus simply blindly trusts the other nodes and the miners that they didn't forge anything. This is extremely risky and a viable attack vector for attacking their blockchain.

Further discussion of Bitcoin's security model, the definition of decentralization, and of that, here: https://hackernoon.com/the-ethereum-blockchain-size-has-exceeded-1tb-and-yes-its-an-issue-2b650b5f4f62

What is called UTXO commitment is radically different from Ethereum's snapshots. The latter is vulnerable to short-range attacks UTXO commitment is not! I read the article you've linked, the day it was published, good statistics about Ethereum but nothing new for bitcoin, the same blind enthusiasm about current bitcoin. Put some real meat on the table, please.

In the scheme that I'm advocating for, nodes do not accept (and relay) a single block without full validation. Guys like you are worried about malicious UTXOs being forged by miners and committed to for hundreds up to thousands of blocks and exploited thereafter, which is really a stupid paranoia. It could also be considered a forgery of concepts to spread FUD about the mining scene of bitcoin for political reasons, again, stupid.

A 51% attack would not let through a double-spend
Last to respond to your question in the thread's title, "Is 51% attack a double-spending threat to Bitcoin?", I guess you have the answer already: It is not.

Why? According to you, it is because full nodes won't allow it but my argument is more solid: It is not gonna happen because it will be revealed anyways and destroy the attacker completely beforehand. Bitcoin inflation rules are currently parts of a social contract, rather than some lines of code, it is hard to understand but you should try.

Cheers,

[aliashraf]

Are we clear? This full-node, full-node propaganda is totally fake and misleading. It is not a campaign in favor of empowering bitcoin users by giving them an opportunity to run a full node, it is just a trick to relying less and less on miners in a baseless and paranoid way: Who in the hell can imagine a scenario in which miners are colliding for 3-4 days to inject a few false UTXOS in bitcoin blockchain? A paranoid or a politician.

I think this is again pretty much a question of what you think bitcoin is. A lot of people out there think a lot of things about what bitcoin is and there are claims from con-marketeers about "Real Bitcoin" "True Vision" etc etc.  If you feel that we CAN trust miners, media can be believed to disseminate trustworthy information, full nodes are not needed etc etc. then there are plenty of other centralized scaling approaches out there.

If we take all these issues on privacy, trust on miners, media etc for granted then you are not in agreement with the privacy and security model of bitcoin made possible because of full nodes.

I think you are now somehow agitated by the previous embracing post of the fake Asterisk id, aren't you? it is what they do, they trigger anxiety and push buttons, be careful.

Bitcoin is what it is and presented in its white paper. The "Full-node! Full-node!" screams are fake and a canonical part of a made-up discourse. Bitcoin is dependent on PoW,  ways far beyond what they are presenting and it means there are lots of opportunities for utilizing PoW to help with crucial problems like the one I suggested above, without compromising a single bit of the security or decentralized nature of bitcoin as far as we are speaking of a world that game theory is applicable the way Satoshi has put it.

Alienating scaling/mass-adoption/decentralization proposals by spreading FUD about PoW is an alien discourse and has nothing to do with bitcoin white paper.

[amishmanish]

I think this is again pretty much a question of what you think bitcoin is. A lot of people out there think a lot of things about what bitcoin is and there are claims from con-marketeers about "Real Bitcoin" "True Vision" etc etc.  If you feel that we CAN trust miners, media can be believed to disseminate trustworthy information, full nodes are not needed etc etc. then there are plenty of other centralized scaling approaches out there.

If we take all these issues on privacy, trust on miners, media etc for granted then you are not in agreement with the privacy and security model of bitcoin made possible because of full nodes.

I think you are now somehow agitated by the previous embracing post of the fake Asterisk id, aren't you? it is what they do, they trigger anxiety and push buttons, be careful.

No, I am actually trying to understand the argument you are making and seems to me that you take a lot of things on good faith for the game theory to work. In the replies above, you have repeatedly said that miners will be kept in check because "community", "media" will know as soon as anything happens. But this has to be detected right? That is what a full node does and in a decentralized system we need more of them.

You then say that SPV nodes are sufficient for this which they clearly are not. SPV nodes themselves rely on full nodes for consensus verification. The only case that possibly stands is that of the network relying on pruned nodes rather than archival full nodes. I am still reading on this pruned nodes vs archival full node comparison in how one is better than the other for the network.

When we are talking about benefits of propagation among non-mining nodes in case mining nodes become unreliable, you said that full nodes are not necessary for propagation too as SPV nodes can provide the network service. But, the important thing is they DO NOT validate. We can agree that SPV nodes aren't much use to the network per se, except for being an easy way to provide wallet services to individual users without downloading the full blockchain.

I am also convinced that in its present state, the network of full nodes is still the best D-day option we have. You took a tangent to your old proposals in denying that but well, an idea is just an idea. It cannot be used to refute the actual requirements for bitcoin network.  

Alienating scaling/mass-adoption/decentralization proposals by spreading FUD about PoW is an alien discourse and has nothing to do with bitcoin white paper.

This is a loaded political statement regarding the bitcoin developers and i personally don't agree with it, whatever my opinion counts for. IMO, there is no "True Vision" in bitcoin whitepaper that needs a zealous following. Satoshi wouldn't have shared his humongous work on a public forum to cypherpunks all over the world in an easy to modify repository if he thought that "his whitepaper" is the end-all for everything.

PS: I think it'd be good if we can continue this somewhere other than "Technical Discussion". I just don't feel qualified enough for this sub in discussing these basics..

[aliashraf]

No, I am actually trying to understand the argument you are making and seems to me that you take a lot of things on good faith for the game theory to work. In the replies above, you have repeatedly said that miners will be kept in check because "community", "media" will know as soon as anything happens. But this has to be detected right? That is what a full node does and in a decentralized system, we need more of them.

For getting rid of a false discourse, one should absolutely remain focused.

1- There is just one hypothetical threat that full nodes can ever detect: illegal inflation of bitcoins. There is no other threat to bitcoin that full-nodes are capable to detect not mentioning their inability to mitigate.

2- Illegal inflation of bitcoin is possible either by allowing multiple copies of a coin to circulate around (double-spending) or by printing bitcoin out of thin air.

3- Both threats are considered existential. A single instance of such a catastrophic event will destroy bitcoin and the whole cryptocurrency ecosystem practically. We are talking about 2 hundred billion dollars being at stake at the time of this writing.

4- In bitcoin, PoW is designed as the solution for this threat with game theory as the backup solution for the centralization possibilities and 51% problem.

5- With the centralization of mining we experienced soon after less than a couple of years from the Genesis, we are existing in the edges of a 51% attack for almost a decade now. Fortunately, game theory is doing well and we are good, for now, and probably for a long time.

6- Centralization of mining because of pools is bad and should be addressed somehow.

7- In the meantime, we have a scaling problem and some other less critical ones like privacy issues, they are to be addressed, as well.

Now here is the problem:
Core devs of bitcoin somehow have become convinced that bitcoin is what it is and there is no hope to do anything disruptive about the two BIG problems: Centralization of Mining and Scaling. They've gone that far to adopt Buterin's stupid Trilemma assertion about denouncing feasibility of solving the two at the same time (with a fake third factor, security, he has added to emulate something he has read in high school, the Combined Gas Law ).

This give-up strategy was first triggered by the embracing raw scaling proposals like th one gave birth to bcash after the scaling debate. People went all-in on the idea of every scaling idea is somehow related to a suspicious centralization agenda, just like bcash.

Well, it was obviously just a stupid and naive generalization, but it got viral and became a part of the culture and now it is time to get rid of it, ok?

One important part of this give-up strategy is the exaggerated and artificial distinction between full nodes and miners. Originally, bitcoin does not make such a distinction between the two, right now bitcoin client code has a built-in mining feature and every full-node is officially (not practically) a mining node too!

The give-up strategy is primarily a give-up on PoW. By advertising full-nodes as the superheroes of security and decentralization, other than getting off-track from bitcoin's most important innovation, Proof of Work, the most revolutionary phenomenon in the 21st century for the least, this strategy is neutralizing any opportunity to improve the situation.

I'm advocating for both: decentralization of mining and scaling bitcoin at the same time but it is very important to note: a decentralized mining scene needs full nodes, many many of them, solo miners are full nodes, remember?
So, I'm the one who truly loves full nodes. The give-up strategist? No, he is just a fake lover.

You then say that SPV nodes are sufficient for this which they clearly are not. SPV nodes themselves rely on full nodes for consensus verification.

This is another misunderstanding:
I said that in a context: A hypothetical scenario in which miners somehow could prove that they are not inflating the supply.

I needed this argument for showing the limits you can push PoW. We need to re-think the whole idea of ignoring PoW.

Alienating scaling/mass-adoption/decentralization proposals by spreading FUD about PoW is an alien discourse and has nothing to do with bitcoin white paper.

This is a loaded political statement regarding the bitcoin developers and i personally don't agree with it, whatever my opinion counts for. IMO, there is no "True Vision" in bitcoin whitepaper that needs a zealous following. Satoshi wouldn't have shared his humongous work on a public forum to cypherpunks all over the world in an easy to modify repository if he thought that "his whitepaper" is the end-all for everything.

One point: I'm not the one who started it, and I'm not the one who continues it. People, dev or not,  should take care of their attitude and behave sanely. The one who starts a war is not always the one who ends it. Politicizing bitcoin development proposals is not my option, it is how you are treated when you are discussing critical issues in bitcoin.