True definition of 'consensus'?

[DGulari]

If 95% signal SegWit - then it goes active.  By what definition is this 95% = 'consensus'?  Who said this?  What if the 5% don't agree with the 95% rule?  What if they only reach 87% and change the rule to 85%?  Where is it written that consensus is 95%? 

Of course the real number is 51% and some time after a fork to settle which is the dominant chain.  95% is such an artificial thing. 

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[DannyHamilton]

If 95% signal SegWit - then it goes active.  By what definition is this 95% = 'consensus'?

95% of the previous 2016 blocks.

Who said this?

• First it was said by the person that suggested it as an activation target
• Next it was said by the person that wrote the segwit activation code.
• Then it was said by the person that chooses which code gets pulled into Bitcoin Core
• Then it was said by everyone that chose to download and run that version of Bitcoin Core

That's how a decentralized open source system like this works.  Consensus means consensus of the users that choose to use the software.

What if the 5% don't agree with the 95% rule?

Then they can mine their own blocks that don't support segwit.  They can fork the blockchain and provide a non-segwit bitcoin with 5% of the hashpower.  Users can choose which fork they want to participate on, the one that 95% of the hash-power is supporting, or the one that 5% of the hashpower is supporting.

What if they only reach 87% and change the rule to 85%?

Then they will need to get the users to all agree to download and run the new software that has the 85% activation target.

Where is it written that consensus is 95%? 

Consensus is 100% of the users that choose to run that version of software.  The creators of segwit decided that they didn't want to try to operate with only 51% of the hashpower, but that they didn't want to wait for 100% of the hashpower either.  It is their opinion that if 95% of the hashpower supports segwit, then the majority will be SO OVERWHELMING that the remaining 5% will likely either switch over to segwit so they can continue to have users or will simply abandon Bitcoin.  Either way, an overwhelming majority of hashpower will be supporting and securing bitcoin with segwit after activation.

Of course the real number is 51% and some time after a fork to settle which is the dominant chain.

The real number is 100%.  100% of the users and miners of the system will be enforcing the rules of that system.  Any that don't will be pushed off onto a separate system.

95% is such an artificial thing. 

Correct.  A number had to be picked.  95% was picked.  It seems like a good number.

[AgentofCoin]

If 95% signal SegWit - then it goes active.  By what definition is this 95% = 'consensus'?  Who said this?  What if the 5% don't agree with the 95% rule?  What if they only reach 87% and change the rule to 85%?  Where is it written that consensus is 95%?  

Of course the real number is 51% and some time after a fork to settle which is the dominant chain.  95% is such an artificial thing.  

Consensus should really be understood to be "pledge to support" versus it's "damage potential"
prior to the soft/hard fork being performed.

If a proposal has a high support (95%), then it is assumed that any "damage potential" is low (5%).
With each lowering support %, it's "damage potential" grows higher.

No one should intentionally hurt the Bitcoin network or it's economies/sub-systems by having
low consensus mechanisms. There are acceptable losses and then there are non-acceptable.
95% has been determined to be the most reasonable to attain while being the safest. If 100%
was truly possible, that would be best, but clearly would be impossible to get in most circumstances.

[mainpmf]

If 95% signal SegWit - then it goes active.  By what definition is this 95% = 'consensus'?  Who said this?  What if the 5% don't agree with the 95% rule?  What if they only reach 87% and change the rule to 85%?  Where is it written that consensus is 95%? 

Of course the real number is 51% and some time after a fork to settle which is the dominant chain.  95% is such an artificial thing. 

You're confusing a very technical idea with the modern notion of democracy. It's not because nowadays most of Western countries are "democracies" based on "the majority rules" that it has to be always the case. It's not because it's done this way currently that it's some kind of absolute or even that it's a good thing.

Fact is that the developers of decided that in order to run without dividing too much the community, it would be important to have a nearly complete support of their work. So when they wrote their code they clearly stated that they wanted 95% of support before it could activate. Of course it's arbitrary, completely. But it's the creator who decided of that and if you don't agree well then you don't run it so you're part of the "5%".
95% is nothing like artificial, on the contrary it's very real because it's an actual line of code defining the limit at which SW can work! That's exactly like saying that you want a decision to be taken not at majority but at extended majority. Which is how important decisions should be made.

[franky1]

democratically 51% would be a win for one side with more votes.

but bitcoin blocks are not as strict as that.
because blocks are mined at a bit of luck.. so even at 51% 'hashrate' there is a luck swing of 10% based on actual blocks..

take the segwit miner vote

26% in red. (lets call that the ruling vote tally)
but there is a variance of +-10% in blue.


so even at 26% the votes are going from 18%-32%

so even if there was 51% scenario for something else.. one part of the day it will be 40 next 60 then 40 then 60.. so a rule has to be based over time.

next,, to make it a clear majority the rule needs to be higher than 51% to ensure the risk of orphans is not as much.
because at 51% it would chop off orphans eventually but literally every other block would get orphaned.

so a high majority =low orphan rate. ofcourse 100% is not realistic(the block luck game). and 51% is orphan hell some have said 75%.. but in the end 95% seemed a clear number that allowed some variance of luck while understanding it would be majority compliance to not cause much if any orphan issues

[mainpmf]

As I see lots of people with deep knowledge of btc functions I'll go a bit further with another question:
What would happen in case of separation?

What will happen if we got 5% of miners that don't want Segwit?
Will we have 2 different bitcoins? Or will it mean that transactions will have to chose between old network and new network and will go through only if they manage to mine a block?
So we would have a fight between the two networks and the hashpower of each will lead to a number of transactions able to go through?

Maybe what I'm saying is a complete nonsense though xD

[Carlton Banks]

As I see lots of people with deep knowledge of btc functions I'll go a bit further with another question:
What would happen in case of separation?

What will happen if we got 5% of miners that don't want Segwit?
Will we have 2 different bitcoins?

Yes. If the 5% carry on with the old block version and rules after the fork, the 95% will reject (aka orphan) their blocks.

Or will it mean that transactions will have to chose between old network and new network and will go through only if they manage to mine a block?
So we would have a fight between the two networks and the hashpower of each will lead to a number of transactions able to go through?

Well, sort of. The choice of network is not made at the time one sends a transaction, it's made when choosing which version of Bitcoin you use. People using pre-fork Bitcoin versions will be on the 5% fork, while those who use the post-fork version of bitcoin will be on the network with 95%.

[Xester]

To get the consensus we must first define what consensus means. Does it refers to all bitcoin users or to all miners. If it refers to all users it is impossible to get a consensus since it is impossible to count the actual numbers of users this day. If it refers to all miners it will be the same problem. Lastly bitcoin is decentralized and there is no central agency that will determine what is the choice being made by the community. For me getting consensus is difficult and saying 95% is vague as how it is derived.

[franky1]

to correct the person 2 posts ago

on a consensus activation. any bitcoin client is still on the same network. just more or less involved in seeing orphans as often.
its the same network but the data each side has, temporarily may differ for a certain time.

its an intentional split (actually blacklisting opposing nodes and not using consensus) that would be on different 'forks/networks'(altcoins)

on a consensus activation
orphaning kills off and drops the minority block that doesnt meet the majority rule. meaning one minute a block shows up with a list of transactions. next minute that block of transactions is gone and another block is in its place that meets the majority rules, picking up those lost transactions (as they are reclassified as unconfirmed until added to a block) either in that new block or another block soon after

hense why in the beginning of an activation of any fork, soft or hard there is an orphan risk so most merchants will wait a few extra confirms to wait and see if a block gets dropped off the chain or not.

most pools drop 1-2 blocks a day-week. and although 1confirm (under 1.44% chance of orphan) is enough for todays rational trust.
in a 95% risk waiting 6-15 confirms(5%-10%) could become the extreme waiting times for confirms.

worse case scenario (doesnt really happen but should be wary of)
during the risky time there are chances of double spending IF a merchant accepts a payment but then its dropped, and that transaction is not then re-confirmed on the replacement blocks (super low chance of happening. as usually pools would re-add the now unconfirmed tx to a new block, reconfirming it, thus giving the merchant the funds eventually)

and (although no one is proposing this) a 51% activation. merchants would wait 12-24 hours(72-144 confirms) due to the mass orphan drama such a low threshold would cause

as for making an altcoin, (different forks) this requires something extra.. actually blacklisting and not connecting opposing nodes.

[DannyHamilton]

. . . For me . . . saying 95% is vague as how it is derived.

Then I suggest you post less and read more. The answer is already in this thread that you are posting in.

. . . By what definition is this 95% = 'consensus'?

95% of the previous 2016 blocks.

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95% is such an artificial thing. 

Correct.  A number had to be picked.  95% was picked.  It seems like a good number.

(Of course you're probably just here to increase your post count, so I doubt you'll ever even see this response)

[mainpmf]

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Ok...
Well thank you both for you answers (especially your detailed one frank1 )
But as a non technician I'm not sure I understood EVERYTHING xD
From what I get the idea is not to separate the network in two, it's not a conflictual change but more an agreement on which type of data each side would consider. So it means that if 95% of miners switch to SG the last 5% wouldn't really have a choice but to switch too no? Otherwise they would have nothing but orphans blocks!
There is just one thing I'm really not sure of, Carlton Banks you say that the choice "is made when choosing the version of bitcoin you use". But... I never made this choice, I got bitcoin but no idea of which "version" they are! Is it my electrum wallet which chose for me (i.e. by using electrum I'm using a certain version of bitcoin without even knowing)?

[franky1]

Ok...
Well thank you both for you answers (especially your detailed one frank1 )
But as a non technician I'm not sure I understood EVERYTHING xD
From what I get the idea is not to separate the network in two, it's not a conflictual change but more an agreement on which type of data each side would consider. So it means that if 95% of miners switch to SG the last 5% wouldn't really have a choice but to switch too no? Otherwise they would have nothing but orphans blocks!
There is just one thing I'm really not sure of, Carlton Banks you say that the choice "is made when choosing the version of bitcoin you use". But... I never made this choice, I got bitcoin but no idea of which "version" they are! Is it my electrum wallet which chose for me (i.e. by using electrum I'm using a certain version of bitcoin without even knowing)?

just holding bitcoin doesnt make you a (in layman's) voter. you need to run a full node to be part of the network.
litenodes and webwallets are just convenient side services. and not part of the real network

electrum(the company/devs) themselves can choose which code version they prefer, and set their main full node(their server) as such, but your use of electrum has no impact on their choice. or on what the consensus becomes.

same with things like coinbase, blockchain.info. you can use any of these lite/web wallets. but the main fullnode that your lite/webwallets connect  to, do not give individual users a vote.

there are estimate 2million+ people with bitcoin. (most mainly hoard coins in webwallet/exchanges)

but there are under 6000 full nodes securing the bitcoin network rules and under 30 mining pools creating blocks that fit the rules.

soft forks only form consensus using the mining pools 'vote'
hardforks form consensus using the full node 'vote' and then if node consensus is reached. the mining pool 'vote'. (double elections to secure real safe victory or defeat)

[Carlton Banks]

There is just one thing I'm really not sure of, Carlton Banks you say that the choice "is made when choosing the version of bitcoin you use". But... I never made this choice, I got bitcoin but no idea of which "version" they are! Is it my electrum wallet which chose for me (i.e. by using electrum I'm using a certain version of bitcoin without even knowing)?

There is only one version (in this specific soft fork scenario), until the fork happens, which it hasn't yet.

As for the choice, it's only relevant if you use dedicated Bitcoin software that at least downloads some part of the blockchain to your computer, as only that type of Bitcoin software typically gives you the choice to run older versions of the overall Bitcoin network protocol. If you had the source code for whatever software you liked best, you could patch in any new fixes and stay away from Segwit features on even a lite wallet for as long as you wanted.

[DooMAD]

But... I never made this choice, I got bitcoin but no idea of which "version" they are! Is it my electrum wallet which chose for me (i.e. by using electrum I'm using a certain version of bitcoin without even knowing)?

If you use Simplified Payment Verification, more commonly referred to as "SPV" or "lightweight" clients, you're relying on other (full) nodes to ensure the blocks they relay to you are correct.  Full nodes verify transactions to ensure they conform to the rules of the network as defined in that version of the full node software.  SPV just keeps the block headers, so in effect receives a pre-approved list of valid transactions, rather than checking the validity itself.  So yes, by using Electrum, you're going with the flow and allowing others to choose for you what rules should govern the network.  

SPV clients will simply follow the longest chain without question and have no say in what the rules are.  Full nodes enforce a ruleset and will ultimately determine which chain is the longest.  Rules only come into force if the rest of the network agrees.  As for the wider matter of "True" definition of consensus, some people still mistake consensus as the developers of full node software agreeing on a ruleset and users running it without question, but this is incorrect and should be challenged at every opportunity.  The definition of consensus is that the users freely choose the code that governs the network.  The ruleset that results in the longest chain at any given time is Bitcoin.

It's peculiar in a way that the Bitcoin whitepaper only uses the word "consensus" once, so it may as well be quoted in the thread:

We have proposed a system for electronic transactions without relying on trust. We started with
the usual framework of coins made from digital signatures, which provides strong control of
ownership, but is incomplete without a way to prevent double-spending.  To solve this, we
proposed a peer-to-peer network using proof-of-work to record a public history of transactions
that quickly becomes computationally impractical for an attacker to change if honest nodes
control a majority of CPU power. The network is robust in its unstructured simplicity. Nodes
work all at once with little coordination. They do not need to be identified, since messages are
not routed to any particular place and only need to be delivered on a best effort basis. Nodes can
leave  and  rejoin  the  network  at  will,  accepting  the  proof-of-work  chain  as  proof  of  what
happened while they were gone. They vote with their CPU power, expressing their acceptance of
valid blocks by working on extending them and rejecting invalid blocks by refusing to work on
them. Any needed rules and incentives can be enforced with this consensus mechanism.

Although the way it's worded seems to vastly understate the role that non-mining full nodes play in determining consensus.  Obviously it's the miners that build the longest chain (again conforming to the rules as defined in their chosen software), but if the rest of the nodes choose not to relay that chain, the miners are wasting their time and hashpower.  Bare this in mind when you see the dozens of threads about mining centralisation and certain countries supposedly "controlling" Bitcoin.  Miners have an important role to play, but other full nodes are equally vital.

[manselr]

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Ok...
Well thank you both for you answers (especially your detailed one frank1 )
But as a non technician I'm not sure I understood EVERYTHING xD
From what I get the idea is not to separate the network in two, it's not a conflictual change but more an agreement on which type of data each side would consider. So it means that if 95% of miners switch to SG the last 5% wouldn't really have a choice but to switch too no? Otherwise they would have nothing but orphans blocks!
There is just one thing I'm really not sure of, Carlton Banks you say that the choice "is made when choosing the version of bitcoin you use". But... I never made this choice, I got bitcoin but no idea of which "version" they are! Is it my electrum wallet which chose for me (i.e. by using electrum I'm using a certain version of bitcoin without even knowing)?

The remaining 5% can do whatever they want... they can join and signal for activating segwit or not. If they don't, it's just a matter of ego. "I'll die with my firm ideas unchanged" sort of mentality. Pretty stupid since by the time segwit hits like 80% the remaining 20% should start considering that they are wrong. Unfortunately it seems we are stuck at 25%, even tho it seems there is a bit of growth but very slowly. Maybe across the year we can get a higher %. Big segwit denniers like Brian Armstrong have recently changed their position and now they support segwit. We will keep seeing this across the year since without segwit nothing will ever change.