How the fork will happen if a fork happens

[AliceWonderMiscreations]

As many of you know, Bitcoin Unlimited is gaining momentum with miners, roughly has 30% of the hash power presently (based on last 1000 blocks, slightly more if you only go back 144 blocks). Additionally, 8 MB block miners have a small but not negligible percentage of the hash power.

There seems to be some confusion about how the fork would take place. It actually is fairly well thought out:

https://medium.com/@ViaBTC/miner-guide-how-to-safely-hard-fork-to-bitcoin-unlimited-8ac1570dc1a8#.t7nul1uz0

There are three steps the fork.

In the first step, miners willing to mine BU blocks simply indicate their willingness to do so. Many of them that are indicating a willingness to do so are probably actually running core, they do not need to upgrade in order to send the flag and it would be expensive to update to BU only to have to revert back to core if BU fork does not happen.

It is not possible to accidentally indicate support for BU, so any miners sending the BU flag are doing so intentionally and thus indicating intent to mine bigger blocks, and that is enough right now.

If 75% of the hash power indicates support for BU consistently for an entire difficulty period (2016 blocks - typically about two weeks) then they enter step two.

For step two, users are prepared for the fork. This will take two difficulty periods (four weeks) giving ample time to get the word out letting users know they will need to run a client that accepts larger blocks. During this four week process, they must maintain 75% of the hash power or the fork does not happen.

So, from the time that 75% of the hash power indicates intent for BU to the time it actually happens is a minimum of three difficulty period, a minimum of six weeks. During that 6 week period, miners that indicate they are with the BU camp will still orphan any blocks that are larger than 1 MB unless it is part of a longer fork with 6 confirmations, and that will only happen if 51% of the total hashing power activate early, not likely to happen.

Once that phase two has passed, then miners will optionally indicate that they are willing to accept blocks larger than 1 MB and build upon them. However the actual fork will not happen until 51% of the total mining power has indicated they accept blocks larger than 1 MB.

It is possible for that to never happen. One malicious scenario is 25%+ of the current mining power indicates they are with BU but is lying. That could prevent the needed 51% of all hashing power needed for a fork to become the longest chain. I doubt that will take place, that would be a conspiracy on par with censorship of users voicing their opinions on Bitcoin related forums. Oh, wait... that's even happened to me. Well anyway I still doubt that will happen.

Once a chain with six blocks built upon a block > 1 MB exists and is the longest chain, then even BU miners who have not changed their configuration will accept it as the valid chain and the fork has taken place.

That is how it will happen. Agree with it or not, it is very well thought out and avoids activation unless there truly is miner consensus on the BU fork.

-=-=-

What does that mean for you, the end user? (and me)?

Run a BU client and whether or not it happens, we are fine. It takes 95% of miner consensus for SegWit to activate, and that clearly is incredibly unlikely to happen. Even if it does happen, we can still use Bitcoin with a BU client - just keep using traditional addresses and you don't need a SegWit capable client, but since miners getting anywhere close to 95% support of SegWit is much farther off than miners sustaining 75% support of BU - there is absolutely no benefit to running a SegWit capable client now unless you are a developer using the test network.

[1715536101]

1715536101

[AliceWonderMiscreations]

It's important to note that if the hard fork happens, core will likely have 25% or less the hash power meaning block confirmation time will likely jump to 40 minutes or more on average. It will take at least one difficulty period, possibly two, for it to get back to a difficulty level where it is at 10 minute block time and it will be susceptible to 51% attacks from the BU miners, though I hope they do not do that. It is however a very real risk and one should always be aware of possible threats.

While the block confirmation time is so long, the core fork will be particularly vulnerable to DoS attacks on its blockchain and I suspect they will happen simply because some mean people will see DoS attacks as a fun way to get rid of their core fork coins. I do not approve of such behavior but I suspect it will happen.

As such, I do not think the core fork will survive very long.

[European Central Bank]

https://bitcointalk.org/index.php?topic=779

from gavin andresen no less talking about this hypothetical scenario where a sect of miners decide to fork away to continue the 50 coin block reward.

I very much doubt that any one entity will ever have 50% of the computational power. The botnet operators will bow to the whims of the community because it's the community that ultimately gives bitcoins value. What good is a giant load of bitcoins if you don't have anyone willing to give you something in exchange for them?

Eventually the largest merchants and money exchangers will control what is "standard" bitcoin.

Take the "50-coiners" scenario, and imagine that they manage to get 75% of the CPU power on their side.

But imagine that the biggest merchants and money exchangers are more conservative, and are in the 25% minority.  I think they will be-- I don't think they'll be the ones in the business of generating coins (they'll be busy selling products or doing the exchange thing).

What happens?

Well, the block chain splits.  Transactions using coins minted before the split will get added to both block chains, and accepted by everybody.

Transactions involving "50-coins" (generated after the split) will be accepted on the 50-coin chain, rejected on the 25-coin chain.  And vice-versa.

"50-coiners" would quickly find out that they couldn't get rid of their newly minted money because who wants bitcoins that are rejected by the biggest money exchangers or merchants?

If the big merchants and money exchangers disagreed, I bet you'd see Bitcoin clients that ONLY accepted pre-split coins and did no coin generation (since those transactions would be accepted by everybody).  If it was never resolved, I think the number of Bitcoins at the time of the split would become "the number of Bitcoins, period,"  because most people will not want to use money that is accepted some places and not others.

technicalities aside, which i don't understand enough of, i have yet to see a single credible bitcoin business or exchange come out on the side of bitcoin unlimited. we've already had the coinbase view which is they'd list it as an alt.

many people may not like the core approach, but they're also practical enough to recognise that they're the ones with the skills. and most everyone else would love to get rid of the cancer that is chinese mining cartels.

[franky1]

many people may not like the core approach, but they're also practical enough to recognise that they're the ones with the skills. and most everyone else would love to get rid of the cancer that is chinese mining cartels.

you do know real consensus is about the nodes..

you do nore core actually avoided that and intentionally chose to give pools the only vote. which nodes officially cannot veto
think about that for a while.

dont jump back to defend core.

think about who gave the pools the voting power.

imagine it the other way. nodes first and pools not allowed to vote until nodes reached X% first

[RHavar]

Personally I would be very happy if such a fork happens. As soon as it does, I will transfer a couple thousands BUC (Bitcoin Unlimited Coins) to the first exchange that supports BUC:BTC  trading, and put an order in to sell my BUC for >= 1 BTC each.

For BUC to survive, it would require the price to be higher than BTC. Even if the price was equal, BUC would die (because for BUC to exist, it requires it having more mining power than BTC. But if it has more mining power and the same price, it'd be more economical to mine on BTC). And as soon as BTC regains more mining work, the BU chain would seize to exist.


It seems like an easy way for me to double my bitcoin holdings. Worst case is I'm wrong, and there's more market demand for BUC than BTC, and the price of BTC is worth very little. But without a doubt the BTC chain will still live on, and still retain some value.

[rapta]

Great read, well put together post.  What if this turns into an ETH / ETH Classic scenario?  That seems very possible at this point.  Both chains can be supported at the same time.

[European Central Bank]

Great read, well put together post.  What if this turns into an ETH / ETH Classic scenario?  That seems very possible at this point.  Both chains can be supported at the same time.

i don't see how it could work like that. eth changes its difficulty super rapidly. that's what allowed a smooth fork. bitcoin's diifficulty only changes every two weeks. that's a yawning gap for things to go wrong.

[RHavar]

i don't see how it could work like that. eth changes its difficulty super rapidly. that's what allowed a smooth fork. bitcoin's diifficulty only changes every two weeks. that's a yawning gap for things to go wrong.

The difficulty might not end up being that big of a deal. Let's say 75% of mining power did decide to fork bitcoin, there's going to be mass confusion and chaos. No matter which side of the fork you support, you're going to want to be extremely careful about sending money to avoid replay issues. (i.e. even if you support BU, you wouldn't want to lose your BTC because they'd still be worth *something*. And vice versa).

For instance, I would likely temporarily halt all withdrawals on bustabit for a day or two if the network forked (to avoid leaking BUC coins).


So with a massive drop off in day-to-day bitcoin transactions, there is probably going to be enough capacity in BTC to continue operating while the big economic players duke it out on the exchanges to see who's coin is worth more.

[rapta]

It is going to take a lot longer than 2 weeks to change the difficulty.  If the reduction of hash power is 75%, it will take at least 4 times as long to move the chain forward.  That is going to highly depend on when exactly the fork occurs (how close it is to the next natural difficult adjustment).

A lot of altcoins experienced this problem a few years ago when multipools were introduced.  Once their coin was no longer profitable to mine, huge amounts of hash power would disappear from the network.

KGW for MegaCoin was one of the first fixes for that issue.

[franky1]

ok guys.

after the 20 minutes of you playing with double your allotment of coins..

..
think passed the selfish greed of the 20 minutes of swapping the coins.

now genuinely think. which will keep bitcoin utility alive and which is just empty promises that only achieve something if you dance around for months

choose what version you prefer based on the actual long term abilities it would bring EVERYONE. not just the few

[pooya87]

Fork does NOT mean Split

please stop using the word "fork" in a context that implies it means split because it really doesn't. it is a possibility that can be a side effect of forking.

- i don't usually get involved in block size related arguments but it really makes me mad when people do this!

[AliceWonderMiscreations]

Fork does NOT mean Split

please stop using the word "fork" in a context that implies it means split because it really doesn't. it is a possibility that can be a side effect of forking.

- i don't usually get involved in block size related arguments but it really makes me mad when people do this!

There will be a split. What happens to the blockchain fork that does not accept blocks > 1 MB is anyone's guess, I do not believe it will survive, but unless close to 100% of the hashing power is on board with BU there will be a split if the hard fork takes place, make no mistake about it.

[ebliever]

Neither Core nor BU are anywhere near hitting the 50% mark much less their respective activation points, which means Bitcoin is stuck in the mud for the foreseeable future. Any edge in miner flagging by BU is negated by the total absence of support I see in both bitcoin media and statements from independent merchants and exchanges so far. Makes me glad I activated my "plan B" in case of the ETF rejection and shifted some BTC to DASH ahead of the rush. I expect that shift to continue until Bitcoin supporters figure out how to address the TX capacity limitation effectively.

Does anyone have a handle on how many of the miners flagging support for BU are actually core supporters (or simply miners disapproving of the BU fork effort) who intend to pull the rug out from under them if they activate? I've seen some evidence folks on Reddit are doing this, but whether it is negligible or significant I have no idea.

[AliceWonderMiscreations]

I can't speak for the media, but as far as exchanges and merchants - they won't have to do anything special unless both forks survive and I find that doubtful.

If this happens, I doubt the fork that sticks with 1 MB blocks will last a month.

Bitcoin support boards are literally full of people asking why their transactions are taking so long. Core's solution isn't going to help them for a long time, they will gladly download a client that provides a working solution to their problem.

Even if SegWit is activated right away on the core fork, users will first have to transfer their value to SegWit addresses before they benefit and that would put an incredible strain on the core fork of the blockchain - which will only be creating blocks every 40 minutes - and cost the users quite a bit of money just in the TX fees as they compete for space on the limited blocks to move their value to SegWit addresses.

And once their traditional addresses are moved to SegWit addresses - LN still isn't here.

If this fork happens, core will crash and burn and users will flock to clients that work with the BU chain.

[Amph]

Fork does NOT mean Split

please stop using the word "fork" in a context that implies it means split because it really doesn't. it is a possibility that can be a side effect of forking.

- i don't usually get involved in block size related arguments but it really makes me mad when people do this!

There will be a split. What happens to the blockchain fork that does not accept blocks > 1 MB is anyone's guess, I do not believe it will survive, but unless close to 100% of the hashing power is on board with BU there will be a split if the hard fork takes place, make no mistake about it.

the consensus is set at 95% for a reason, it's to prevent regression to the old fork, it mean that if an hard fork happen because we reached the proper consensus

the other chain will simply result in an altcoin, and the only remaining one will be the one that matter, i dunno why there is still someone who believe that we would end up with two active bitcoin chain...

yes the other chain might have a value but that is an altcoin story there...

[Mitcsell]

Fork does NOT mean Split

please stop using the word "fork" in a context that implies it means split because it really doesn't. it is a possibility that can be a side effect of forking.

- i don't usually get involved in block size related arguments but it really makes me mad when people do this!

There will be a split. What happens to the blockchain fork that does not accept blocks > 1 MB is anyone's guess, I do not believe it will survive, but unless close to 100% of the hashing power is on board with BU there will be a split if the hard fork takes place, make no mistake about it.

the consensus is set at 95% for a reason, it's to prevent regression to the old fork, it mean that if an hard fork happen because we reached the proper consensus

the other chain will simply result in an altcoin, and the only remaining one will be the one that matter, i dunno why there is still someone who believe that we would end up with two active bitcoin chain...

yes the other chain might have a value but that is an altcoin story there...

I do not know too much about crypto currency and try to learn as much more to know all the risks and prospects in the future. I can not understand the real threat of Bitcoin's Splitting as a result of hard fork. Why does everyone think about this will lead to serious consequences and will there be a real threat to the crypto currency?

[AliceWonderMiscreations]

Fork does NOT mean Split

please stop using the word "fork" in a context that implies it means split because it really doesn't. it is a possibility that can be a side effect of forking.

- i don't usually get involved in block size related arguments but it really makes me mad when people do this!

There will be a split. What happens to the blockchain fork that does not accept blocks > 1 MB is anyone's guess, I do not believe it will survive, but unless close to 100% of the hashing power is on board with BU there will be a split if the hard fork takes place, make no mistake about it.

the consensus is set at 95% for a reason, it's to prevent regression to the old fork, it mean that if an hard fork happen because we reached the proper consensus

the other chain will simply result in an altcoin, and the only remaining one will be the one that matter, i dunno why there is still someone who believe that we would end up with two active bitcoin chain...

yes the other chain might have a value but that is an altcoin story there...

The consensus for the BU hard fork though is at 75%, not 95%.

[rapta]

Fork does NOT mean Split

please stop using the word "fork" in a context that implies it means split because it really doesn't. it is a possibility that can be a side effect of forking.

- i don't usually get involved in block size related arguments but it really makes me mad when people do this!

There will be a split. What happens to the blockchain fork that does not accept blocks > 1 MB is anyone's guess, I do not believe it will survive, but unless close to 100% of the hashing power is on board with BU there will be a split if the hard fork takes place, make no mistake about it.

the consensus is set at 95% for a reason, it's to prevent regression to the old fork, it mean that if an hard fork happen because we reached the proper consensus

the other chain will simply result in an altcoin, and the only remaining one will be the one that matter, i dunno why there is still someone who believe that we would end up with two active bitcoin chain...

yes the other chain might have a value but that is an altcoin story there...

I do not know too much about crypto currency and try to learn as much more to know all the risks and prospects in the future. I can not understand the real threat of Bitcoin's Splitting as a result of hard fork. Why does everyone think about this will lead to serious consequences and will there be a real threat to the crypto currency?

Yeah the main issue is getting the majority to agree.  Normally that's not a difficult situation, but when dealing with software development, and "currency", it can really complicate things.

[RHavar]

The consensus for the BU hard fork though is at 75%, not 95%.

Actually no it's not. That's one of the reasons BU or "emergent consensus" is so silly. There's literally no consensus threshold or specific time or block height the hard fork happens.

[Wind_FURY]

Fork does NOT mean Split

please stop using the word "fork" in a context that implies it means split because it really doesn't. it is a possibility that can be a side effect of forking.

- i don't usually get involved in block size related arguments but it really makes me mad when people do this!

You are right but in some cases forks really do mean forking away from the network. The same was said about Ethereum. The Ethereum foundation said everything will be ok, that a split happening was impossible because of X and Y using fancy technical terms.