Bitcoin protocol upgrade (hard fork) FAQs

[BitcoinXio]

This was originally posted to /r/btc but I thought it would be good to post it here too as I think there are readers here who aren't on reddit.

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There has been a lot of forking-related questions recently. This thread serves to provide a platform to talk about forking and what it means to you as a Bitcoin user. Just like with everything, this is a work in progress and we need the community’s input on what it should contain. The below is just a primer. If you want to add to it, please leave a comment below with what you want to add. If you have general questions about forking, feel free to post that in this thread’s comments too and others will try to answer.

What is a hard fork?

A hard fork is when a block is broadcast under a new and different set of protocol rules which is accepted by nodes that have upgraded to support the new protocol. In this case, Bitcoin diverges from a single blockchain to two separate blockchains (a majority chain and a minority chain).

There will be two blockchains after a fork, is that right?

Yes, that is correct. Some argue that having two chains is problematic, but that is only the case if you believe that the minority chain will survive and have more market value than the majority chain.

Is a hard fork bad?

Hard forks are just protocol upgrades. If you want to have a better designed Bitcoin protocol, periodically you will have to upgrade (fork) to make it happen. A planned fork is nothing to panic about. In fact, just like with Bitcoin halving every four years, protocol upgrades can be celebrated too.

What will happen to my bitcoin when a fork happens?

Don’t worry, your bitcoin is safe! The most important thing as a user who wants to control their own money (bitcoin), is that you will want to store your bitcoin in a wallet where you have control over the private key. As long as you do that, post-fork you can spend your coins however you’d like. But if you leave your coins on an exchange for example where you may not have control over your private key, post-fork the exchange will have to determine which blockchain your coins belong to.

When will the fork happen?

Every fork is different, so generally speaking there isn’t one answer that can fit every scenario. Most recently the protocol upgrade that has caused the most news has been Bitcoin Unlimited (BU) and the consensus mechanism emergent consensus, which removes the temporary Bitcoin block size limit like the original client and lets the free market decide what block size is best, allowing for on-chain scaling. BU doesn’t have a set activation period. Once there is consensus among Bitcoin user nodes and mining nodes that signal an acceptable block size using BU, the blockchain will begin to diverge. For more information for miners on how to safely fork to BU, please read the ViaBTC Miner Guide.

Has a hard fork ever happened before?

Forks have successfully been implemented often in other cryptocurrencies. In fact there are very few instances of hard forks failing. On the Bitcoin blockchain there has already been one successful hard fork in the past. This hard fork was carried out in response to a serious bug found in Bitcoin that could be used to create billions of bitcoin. A hard fork was planned and carried out in a short amount of time to fix this big.

Why is a hard fork likely to happen?

A fork is likely to happen due to a fundamental disagreement between different groups of the Bitcoin community on how the Bitcoin protocol will progress in the future. A long and important debate has carried on within the community for the past several years and consensus has been unable to be found on a path forward. A hard fork is one method for finding a way forward using using *Nakamoto Consensus*; read the Bitcoin whitepaper to understand the underlying architecture of how Bitcoin was built.

I’ve heard about replay attacks when forking, what are they?

When there is a chain split, you may end up with coins on both sides of the blockchain (two coins), for example Bitcoin Core (BTC-C) and Bitcoin Unlimited (BTC-U). A replay attack is when a user broadcasts both coins on both blockchains, taking advantage of exchanges that might not have protection against these attacks. Recently exchanges have reached out to the Bitcoin community for suggestions on the best way to handle these situations.

How can I keep track of the ongoing consensus finding of the fork?

There are many sites to keep track of how people are voting within the community. For example you can see how people are economically voting, how miners are signaling (also over last 1000 blocks), and how user nodes are signaling. If you're unsure, you can always submit a post and ask your peers what they think!

Thanks to the following people for helping with the questions/answers:

/u/singularity87
/u/todu
/u/Bitcoinopoly
/u/Erik_Hedman

[patrick.miller]

A hard fork is not only a protocol upgrade. Hard forks were done in the past to fix bugs in the code that caused the network to inadvertently fork.

This is very different from a contentious hard fork. The fact that you omit information means that you are purposely misinforming new people.

You know what I am talking about, so don't bother responding with some nonsense you have made up.

BTU will never be accepted as BTC. The community will not allow it. Even if you obtain 51% of mining power, the nodes, wallets, exchanges will reject it.

We will not allow a 51% attack from a centralized ASIC manufacturer and mining cartels running broken software from closed-source "developers"

[BitcoinXio]

Hard forks were done in the past to fix bugs in the code that caused the network to inadvertently fork.

This is precicly what emergent consensus is looking to do, fix the 1MB limit (it's a bug, certainly not a feature) through a protocol upgrade.

This is very different from a contentious hard fork. The fact that you omit information means that you are purposely misinforming new people.

You mean like how Segwit is a contentious fork but yet I don't hear much about that from the Core side. Hmm...

We will not allow a 51% attack from a centralized ASIC manufacturer and mining cartels running broken software from closed-source "developers"

Who is "we"? Because Blockstream and Bitcoin Core representatives have all worked tirelessly over the years trying to persuade miners to work in their favor. Now that the tables have turned, it's no longer okay? Right, got it.

[Rmcdermott927]

The interesting thing about a BU hard fork is that it will likely trigger a segwit activation on the core chain as that will consist of supporters.

The fork won't be the end of the debate, we will likely see both chains in competition for a while.

[patrick.miller]

This is precicly what emergent consensus is looking to do, fix the 1MB limit (it's a bug, certainly not a feature) through a protocol upgrade.

The 1 mb limit is not a bug.

[patrick.miller]

The interesting thing about a BU hard fork is that it will likely trigger a segwit activation on the core chain as that will consist of supporters.

The fork won't be the end of the debate, we will likely see both chains in competition for a while.

Which is why BU could have forked long ago, because the end result is the same. But instead, BU and Bitcoin.com has chosen to FUD Bitcoin and cause the price to drop.

The majority of nodes will always be Core nodes. The community is not Roger Ver and his paid employees and centralized mining cartel.

[Dynamix]

Well this will be interesting to see if they will actually Hard Fork btc , if it does I will short that until $500 haha

[BitcoinXio]

This is precicly what emergent consensus is looking to do, fix the 1MB limit (it's a bug, certainly not a feature) through a protocol upgrade.

The 1 mb limit is not a bug. This is exactly the ridiculous response I expected from you.

Let me guess, you aren't a developer and are relying on what Core developers are telling you, right?

A software bug is an error, flaw, failure or fault in a computer program or system that causes it to produce an incorrect or unexpected result, or to behave in unintended ways. Source: https://en.wikipedia.org/wiki/Software_bug

If you think that the 1MB temporary limit is not a flaw that is causing unintended consequences, then you are severely misguided.

[BitcoinXio]

Well this will be interesting to see if they will actually Hard Fork btc , if it does I will short that until $500 haha

Hard forks should be celebrated like Bitcoin Halving events. There is no reason to make it contentious to upgrade the protocol. All software has to be upgraded from time to time. It's ludacrious to believe that we cannot upgrade the Bitcoin protocol.

[lethos3]

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