Bitcoin thought experiment

[Isambard789]

I was wondering how many people on here really believe in the 'longest chain wins' philosophy or whether it is only because it largely matches a 'first to publish' in the long term?

For example, if it turns out that what we currently believe to be the longest chain is suddenly and unexpectedly demoted to a side chain with the appearance of a new chain which goes back, say, 3-6 months. Would you accept this as the 'true' chain or would you push for reverting or locking to the chain that has been publicly seen?

[~Bitcoin~]

I cant get what op is trying to express can anyone get what is he trying ti say? With sidechain in post i think he is trying to compare between bitcoin and altcoin.

[unamis76]

The blockchain isn't going back 3 months out of the blue... When forks happen they're quickly discarded. If you're not on the largest chain, you're losing out.

[Snail2]

I was wondering how many people on here really believe in the 'longest chain wins' philosophy or whether it is only because it largely matches a 'first to publish' in the long term?

For example, if it turns out that what we currently believe to be the longest chain is suddenly and unexpectedly demoted to a side chain with the appearance of a new chain which goes back, say, 3-6 months. Would you accept this as the 'true' chain or would you push for reverting or locking to the chain that has been publicly seen?

New long chains not used to turn up suddenly. You would need a hard fork and the split of the network to form such alternative chains, so everybody would be aware of what happening.

[Amph]

the longest chain issue, is actually another problem that lead to the insecurity of the network byt allowing the 51% attack, so it's something that should be fixed one day, not a priority for now

so i'm a bit against it, i would be with a system that see the best and the legit chain as the one were the last valid block is submitted, based on the history of the previous blocks

so if an entity is suddenly mining all the block you know that someone is trying to do the 51%

[shorena]

I was wondering how many people on here really believe in the 'longest chain wins' philosophy or whether it is only because it largely matches a 'first to publish' in the long term?

For example, if it turns out that what we currently believe to be the longest chain is suddenly and unexpectedly demoted to a side chain with the appearance of a new chain which goes back, say, 3-6 months. Would you accept this as the 'true' chain or would you push for reverting or locking to the chain that has been publicly seen?

The bitcoin nodes would switch to that different chain. The question - as others have brough up already - is where does this new chain come from. "The longest chain" is just an abstraction of what really happens. The number of blocks is not as important as the work that had to be done to find them. Thus a longer chain would only be possible if someone could amass as much mining equipment in secret as is currently used worldwide. This is no simple nor cheap task.

[Kprawn]

I was always under the impression that the two chains will run along side each other and eventually become one chain. All transactions on the shortest chain would then be absorbed on the longest

chain, making double spends impossible. The nodes on the shortest chain, will then have to decide if they going to continue mining a Alt coin or switch to the software running on the longest chain. I

still have a lot to learn and research, when the technical aspects of a hard fork happens. 

[bitdumper]

Getting an sudden alternarive chain 3 months long will require the computing power used in those three months
If you see the current hashing power , it is practically impossible.
But theoraticaly possible.
If somehow that occurs , who will accept that chain ??
Nobody will accept and loose money.

[ATguy]

Thats good question. You should accept the longest chain even if it comes suddenly online with 3 months of blocks, because if you dont, you risk to be on invalid chain any time in future (if it continue to be longest) even if there is central decission NOW to make such longest chain selectively invalid (I cant imagine consensus for making that longest chain selectively invalid though).

[Isambard789]

I was wondering how many people on here really believe in the 'longest chain wins' philosophy or whether it is only because it largely matches a 'first to publish' in the long term?

For example, if it turns out that what we currently believe to be the longest chain is suddenly and unexpectedly demoted to a side chain with the appearance of a new chain which goes back, say, 3-6 months. Would you accept this as the 'true' chain or would you push for reverting or locking to the chain that has been publicly seen?

The bitcoin nodes would switch to that different chain. The question - as others have brough up already - is where does this new chain come from. "The longest chain" is just an abstraction of what really happens. The number of blocks is not as important as the work that had to be done to find them. Thus a longer chain would only be possible if someone could amass as much mining equipment in secret as is currently used worldwide. This is no simple nor cheap task.

It's a thought experiment, but let's say for the sake of argument, that a number of miners with >51% hashing power has been mining in parallel for 3 months, but were not connected to the 'known' network and then later join the network and have the longest chain. Would we be happy to accept this?

From their point of view, we join them and have a shorter chain.

[shorena]

I was wondering how many people on here really believe in the 'longest chain wins' philosophy or whether it is only because it largely matches a 'first to publish' in the long term?

For example, if it turns out that what we currently believe to be the longest chain is suddenly and unexpectedly demoted to a side chain with the appearance of a new chain which goes back, say, 3-6 months. Would you accept this as the 'true' chain or would you push for reverting or locking to the chain that has been publicly seen?

The bitcoin nodes would switch to that different chain. The question - as others have brough up already - is where does this new chain come from. "The longest chain" is just an abstraction of what really happens. The number of blocks is not as important as the work that had to be done to find them. Thus a longer chain would only be possible if someone could amass as much mining equipment in secret as is currently used worldwide. This is no simple nor cheap task.

It's a thought experiment, but let's say for the sake of argument, that a number of miners with >51% hashing power has been mining in parallel for 3 months, but were not connected to the 'known' network and then later join the network and have the longest chain. Would we be happy to accept this?

From their point of view, we join them and have a shorter chain.

I dont know about user happyness, but the nodes would switch the chain, yes.

[DannyHamilton]

Would we be happy to accept this?

Perhaps some would, but most would not.

It's not so much that they would be upset about their confirmed transactions suddenly becoming unconfirmed (or even invalid).  Certainly that would happen to a number of people and those people would be unhappy.  However, the more important issue here would be that the incentives built into the protocol would be proven insufficient.  This lack of sufficient incentive would destroy a lot of faith in why bitcoin works, and as such would destroy the foundation on which the use of bitcoin as a currency stands.

There is a built in incentive for miners to cooperate and mine on the currently longest block.  If you were secretly mining (and not broadcasting your blocks) you run a risk that the public network surpasses you and you lose all the revenue from all those blocks that you otherwise would have received.  There is a large expense in mining. The revenue from the published blocks is needed to offset that loss. The protocol operates under the assumption that the risk of losing the block reward from not publishing is enough of an incentive for miners to publish their blocks.  Additionally, if the secret blocks don't include the transactions, then the cabal of secret miners miss out on all the transaction fees.  If they do include the transactions, then the effect on the typical bitcoin users will be much smaller since most all of the transaction will be confirmed in both chains.

[Isambard789]

Would we be happy to accept this?

Perhaps some would, but most would not.

It's not so much that they would be upset about their confirmed transactions suddenly becoming unconfirmed (or even invalid).  Certainly that would happen to a number of people and those people would be unhappy.  However, the more important issue here would be that the incentives built into the protocol would be proven insufficient.  This lack of sufficient incentive would destroy a lot of faith in why bitcoin works, and as such would destroy the foundation on which the use of bitcoin as a currency stands.

There is a built in incentive for miners to cooperate and mine on the currently longest block.  If you were secretly mining (and not broadcasting your blocks) you run a risk that the public network surpasses you and you lose all the revenue from all those blocks that you otherwise would have received.  There is a large expense in mining. The revenue from the published blocks is needed to offset that loss. The protocol operates under the assumption that the risk of losing the block reward from not publishing is enough of an incentive for miners to publish their blocks.  Additionally, if the secret blocks don't include the transactions, then the cabal of secret miners miss out on all the transaction fees.  If they do include the transactions, then the effect on the typical bitcoin users will be much smaller since most all of the transaction will be confirmed in both chains.

I guess there are also different potential scenarios. One is the malicious version where a group hides his work. The other maybe if some miners are cut off, e.g. if the Chinese miners get temporarily cut off by the great firewall of China or some other network event. True, it is unlikely to but cut off for any length of time, but even in the malicious case, in principle, we should still take the malicious chain and build on it.

But human instinct may say no and keep the 'known' chain, in which case the underlying principle of bitcoin is compromised.

[yenxz]

I was wondering how many people on here really believe in the 'longest chain wins' philosophy or whether it is only because it largely matches a 'first to publish' in the long term?

For example, if it turns out that what we currently believe to be the longest chain is suddenly and unexpectedly demoted to a side chain with the appearance of a new chain which goes back, say, 3-6 months. Would you accept this as the 'true' chain or would you push for reverting or locking to the chain that has been publicly seen?

i dont really understand with your experiment can you tell me more clear about this?or anyone can explain to me this experiment with more simple words?

[Isambard789]

It seems that Ethereum are undergoing an analogous experiment right now...

[Isambard789]

This piece articulates precisely my thoughts on the matter (similarly for bitcoin blockchain mechanism). Ethereum fell at the first hurdle and have gone against the principle of the electronic contract being the only and final arbiter and undermining a major reason for using Ethereum at all.

I wonder how long until bitcoin will need to ask itself the question of whether it truly believes in fundamental principle of 'longest chain wins'? I suspect if it was tested, bitcoin would also not adhere to its core (the longest chain wins) principle.