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64 votes
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What is a soft fork? What is a hard fork? What are their differences?

What is a Project Fork? A fork in software development refers to the event of an independent project spinning off from a software project. Such forks sometimes occur in the opensource sphere, when ...
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44 votes
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How does Bitcoin Cash implement replay protection?

Bitcoin Cash (aka Bitcoin ABC aka UAHF) provides two methods of replay protection, both of which are opt in. If you do not create transactions which use these features, then your transactions are ...
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  • 60.6k
32 votes

What is a soft fork? What is a hard fork? What are their differences?

Softforks are forwards-compatible Old nodes will accept blocks created by new nodes. With a softfork, only miners will have to upgrade, or else they will end up on the losing fork. Users and ...
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18 votes

What is a soft fork? What is a hard fork? What are their differences?

I found the best exact definition in the First three paragraphs here: gavinandresen / BitcoinVersioning We recently rolled out two changes to the Bitcoin block acceptance rules (BIP16 and BIP30); ...
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  • 281
15 votes

What happens if two miners mine the next block at the same time?

What Nicolai said is not completely right. The network would decide which one is the main chain according to the following block mined. Let's assume that block A and B are mined at almost the same ...
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  • 151
15 votes

When bitcoin forks, how do they decide which fork gets the original name?

One might think that the network maintaining the same consensus rules would be considered the original, and the project introducing a consensus rule change and thus creating a new network would be ...
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13 votes
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Can the blockchain be outpaced by a chain of low-difficulty blocks?

There are two problems with this: The "longest" block chain is selected not by total number of blocks, but by total difficulty. A chain with a large number of low-difficulty blocks would not win. ...
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12 votes
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Strongest vs Longest chain and orphaned blocks

The "longest" chain is the one with the most work. A chain's work is equal to the expected number of hashes it would take for someone to replicate a chain of the same number of blocks and the exact ...
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  • 8,684
12 votes
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What is transaction replay and replay protection?

What is a transaction replay In the context of forks, transaction replay is when a transaction is valid on both sides of the fork. So a transaction can be played (i.e. broadcast) on both chains after ...
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11 votes
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What is SPV mining, and how did it (inadvertently) cause the fork after BIP66 was activated?

SPV mining is the term commonly used for 'less-than-full-node-validation' mining. It usually means that miners skip the verification of the block and the transactions within, and immediately start ...
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  • 13.7k
10 votes

Testing blockchain forks

You can use the invalidateblock RPC commands to create blockchain forks. invalidateblock hash tells a node to consider hash invalid, so just generate a bunch of blocks, invalidate one somewhere down ...
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10 votes

What happens to coins after Bitcoin Cash fork?

If you have 1 Bitcoin (BTC) before the hard fork, you will have 1 Bitcoin (BTC) and 1 Bitcoin Cash (BCC) after the hard fork. Whether you can spend those BCC depends on who has control of your ...
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  • 315
10 votes
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Preparing for Bitcoin Gold

Yes Coinbase has not mentioned supporting Bitcoin Gold or Not so to be safe definitely move your BTC to a wallet so you have control of your private keys. On Oct 25th the fork will happen and on ...
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9 votes
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Why doesn't bitcoin place additional constraints on competing block chain forks, other than length of chain? (e.g., time and confirmation count)

My question then is: why doesn't bitcoin specify a maximum duration of time and/or a maximum number of confirmations, after which a competing/forking block is rejected even if it's backed by a longer ...
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  • 28.6k
9 votes

How can forks coexist even though only one of the is the longest chain?

For one, Litecoin is not a fork of Bitcoin. It relies on the same base code, but it is a separate network, and they do not share the genesis block. Bitcoin Cash is a true fork of Bitcoin, in the ...
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  • 16.4k
8 votes

Why doesn't bitcoin place additional constraints on competing block chain forks, other than length of chain? (e.g., time and confirmation count)

First, a quick clarification: assuming two chains both have valid blocks, it's the chain with the most proof of work that wins, not necessarily the chain with the most blocks. Second, thanks for the ...
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8 votes
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How is a blockchain split resolved?

You're looking for CBlockIndexWorkComparator, which operates by three rules. The rules are applied one at a time, and if a rule leads to a tie, then the next rule is applied. Which blockchain has the ...
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8 votes
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Is there actual consensus on the blockchain's tip or only until the next block?

No, there is no consensus until the next block is found. The network is experiencing a blockchain-fork. It will only mend once one of the tips pulls ahead by adding another block. Then all nodes will ...
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8 votes
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Does my bitcoin multiply with every fork?

Note that the word "fork" can have several meanings. The more common one is a protocol change (either a soft or hard fork) where everyone switches to the new protocol. In this case there will still be ...
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7 votes
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Can a shorter chain overcome a longer one?

Background info: Strongest vs Longest chain and orphaned blocks How does a client decide which is the longest block chain if there is a fork? Where exactly is the "off-by-one" difficulty ...
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  • 13.7k
7 votes
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What is the probability of forking in blockchain?

Actually, it is not related to the difficulty at all, rather just related to the expected time until the next block is found. Block finding is a Poisson process. The probability of x blocks occuring ...
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  • 62.5k
7 votes
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Does bitcoin have the potential to be subject to a hard fork where miners are forced to choose which fork they will accept, like Etherum?

Yes, Bitcoin could also be subjected to a hardfork. In fact, there are members of the Bitcoin community that feel so strongly that the blocksize should be increased that they are proposing to do just ...
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  • 62.5k
7 votes
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At what point does a hard fork occur?

A hard fork is something that happens when some of the nodes on the network follow a new set of rules that are in some way incompatible with the existing set of rules. It occurs upon mining the first ...
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  • 8,724
7 votes
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Can I claim my BCH if my BTC is held with Coinbase?

If you didn't move out your BTC before the fork, then your BitCoin Cash tokens remain with CoinBase. They are not really lost, but they might remain in their system for a while. Here is the ...
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  • 86
7 votes
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How does Bitcoin Gold implement replay protection?

I don't believe any replay protection has yet been implemented, they still have an issue open for it on the BitcoinGold repository here: https://github.com/BTCGPU/BTCGPU/issues/51 I haven't dug into ...
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  • 11.3k
7 votes

Is there a list of Bitcoin Forks?

There is this list on Wikipedia: https://en.wikipedia.org/wiki/List_of_Bitcoin_forks Bitcoin Cash (Forked at Block 4785591, 1 August 2017) Bitcoin Gold (Forked at Block 491407[2], 24 October 2017) ...
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7 votes
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Does a 2009 node sync the whole bitcoin blockchain

In theory it can as the explicit consensus rules have not changed. However in practice, it will not be able to sync without some special modifications. First of all, the network version is so old ...
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  • 60.6k
6 votes
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Is there any way to make an UTXO that cannot be spent until a certain block #?

No, there isn't currently any way to do what you describe without using a third-party oracle. Yes, you may be able to do this relatively soon. A soft fork has been proposed to introduce a ...
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6 votes

Which blocks get to be checkpoints?

At least in Bitcoin Core, none. Checkpoints are legacy and will likely be removed at some point. Checkpoints were originally introduced as a way to enable skipping of signatures in the historical ...
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6 votes

Has a hard fork ever occurred?

So which is it? Does "hard fork" describe a condition of the network, or a software update? Either is acceptable. You can say that version so-and-so causes a fork, and you can say that the network is ...
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  • 28.6k

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