do you know how can I add an user to a topic? ?How do I tag? Thank you.
I understand the process might be a bit difficult to grasp. Since youâre creating tx on the blockchain youâre not really using any second layer.
The rule is there to address the physical distances between the nodes and time it takes for blocks to propagate through the network.
These types of forks are in fact rare, they occur less than once a year and for the most part they are not an issue, If youâre buying coffee with Bitcoin you donât have to wait for more than one tx, however if youâre buying a lambo it would be a good idea to make sure the tx is settled. 
You might want to check out this video:
https://www.youtube.com/watch?v=vZ9Vre8T6qw
You use an @ before the username. 
2 Likes
No he doesnât have to do anything. But he can. This is also called a double spend attack. If the tx is still in the mempool, the sender could create a new transaction sending the Bitcoin back to himself and effectively steal the money from the receiver.
There arenât any events or such that are triggered by nodes in that case. So its up to the wallet implementation to alert the user if this occurs. I think most wallets donât really do that, but Iâm not sure because I never sent a tx that would end up in a stale block because these occurrences are quite rare.
The tx can be invalidated while its still in the mempool. This means the tx is still pending which means its not done.
In fact tx on Bitcoin are never really 100% âdoneâ, it all boils down to probability. The deeper down the blocks the tx is buried the less chance the tx will get invalidated. So after 6 blocks the probability of tx being dropped is close to 0.
Kind of like collisions in hash functions, same day we might get the same hash from two inputs but the probability of this being the case is extremely low, or a user might randomly generate the same private key. But with today technology its more probable the universe will end first
2 Likes
This may be a stupid question, but weâve only talked about changing the maximum block height in hard and soft forks. Can we also change the minimum block size?
There is no minimum size for a block. A block can be empty if there are no tx - except for the coinbase ofc.
1 Like
Hello, fam!
I just finished the forks track, I understand all the info thatâs been provided, but I have some additional questions.
Questions on the update forks: Who makes the updates and who has to agree with the updates? Miners? Nodes? All miner? All nodes? Or a certain percentage?
Another question: When an update causes a hardfork to split the chain, does that mean we will now have two different crypto currencies? As Philip mentioned when community split when there were updates such as Bitcoin Diamond or Bitcoin cash, does that mean it happens every time we have hardforks?
Thank you!
Have a lovely day everyone!
1 Like
The change is first discussed by the community, most often on bitcointalk forum. Then they are drafted into a BIP proposal as explained in BIP1 after that they are further discussed end eventually implemented (or not).
In case there is there is a major disagreement between two camps a hard fork might occur that will split the community in two which results in two currencies with the same history. If however there is full consensus and 100% of the people upgrade their nodes then the hard fork will not result in a split (on Bitcoin it does more often).
A good example of a coin where the community doesnât split is Monero, which has constant hard forks to remain ASIC resistant but hasnât ended up in a split chain.
3 Likes
Hi Filip!
I had a question regarding hard forks. Letâs say that I had a wallet with some UTXOâs in the Bitcoin chain before the BCH fork. Do I, after the fork, have funds at both chains that can be signed with the same private key? It kinda seems like creating new money out of nowhere.
Thanks!
Yes you would have coins on both chains because they have a common history.
The video for soft fork confused me because you included the 0.5mB with 1mB boht in blue colours and my head canât get the grasp of it, please update this video as this is the only way I will understand the soft fork fully, the same colours really make it more complicated to digest.
Hello Filip,
Just watched the lecture on hard forksâI am a bit confused!
Context: On the lecture example, the block size <= 2MB were previously rejected by the consensus rules. After an update, the block size <= 2MB is now accepted by the consensus rules and therefore upended to the Blockchain.
Q.1. Does the consensus update comes from the mining level or from the nodes level?
Q.2. Who has the power to accept or reject an updated version of the consensus rulesâminers or nodes?
Q.3. If miners are the ones forming new blocks, how comes nodes play a role in the block formation and upending? It seems that the terms miners and nodes are used interchangeably. By the end of the lecture I understood that nodes also upend blocks to the BlockchainâI am confused, can you please puzzle me out? See, Blockchain Updates & Forks: lecture 5, 5:00 onwards.
a) I understand that a hard fork is caused by updates in the consensus rules that make previous invalid rules now valid or vice-versa i.e. blocks or transactions that were previously invalid are now valid or vice-versa;
b) I also understand that consensus updates are not restricted by latency issues because in the end of the day all nodes would eventually synch with the updated version of the consensus.
Many thanks,
NaraneJr.
Hello! I already watched the video of hard forks and I have a few questions about it.
-
When a hard fork happens can it be solved? The chain got split in two but will it be solved? In case of accidental forks itâs just a matter of time to solve the fork, but in hard forks what happens?
-
What will happen with the reward of the miners that are creating blocks in the chain not updated?
-
If the chain split in two itâs possible that one person has UTXOâs in both chains? What does that mean? Have BTC and another coin?
-
If the chain creates 2 different currencies what will happen with the valor of the second currency? One currency will be BTC but the other one what will be? What is the value of that currency?
-
Supposing that the split creates two currencies, one will be cheaper when itâs compared to the other? This means that some wallets will lose money? If miners select the transactions from the mempool itâs possible that some of those can be used in the chain not updated? If that is the case what will happen?
-
The split creates different currencies with different mempools and systems? How itâs the procedure?
-
Updates affect the entire chain or just the part of chain thatâs created after the update?
For a hard fork to be adopted, a sufficient number of nodes need to update to the newest version of the protocol software. This allows them to use the new coin and blockchain. Any nodes that chose not to update will be unable to use the new blockchain. If enough users donât update then you will be unable to get a clean upgrade which could lead to a break in the blockchain.
Holders of the âparentâ cryptocurrency end up with an equal number of forked-off coins. For example, if you had held 10 Bitcoin at the time of the Bitcoin Cash fork, you would have 10 Bitcoin Cash. This can lead to some really interesting waves within the market.
After fork happened it doesnât mean that both coins will have the same value. Each coin will have its own price after the split, based on supply and demand.
Itâs always a good idea to store your coins in a hardware wallet, but in times of a hard fork it could be even more convenient. When a new coin gains enough support from the community, hardware wallet manufacturers like TREZOR and Ledger for example are usually the first providers to develop a splitting tool. Such a tool can be used to split your coin in the old and new one.
a fork is simply a change in the blockchainâs protocol that the software uses to decide whether a transaction is valid or not. So this new blockchain will have a new set of rules for consensus and if sufficient nodes updated the version of the software protocol the newcoin will survive. The new chain will have its separate mempools.
It affects the chain before the fork.
1 Like
@filip - A fork means two blocks at the same block height , so the ongoing blockchain will have all the blocks with 2 blocks at each block height or it is possible that one or two blocks are only forked and have multiple blocks at that height. And how does the merging happens from 2 blocks to one next block
Both nodes and miners must update their nodes to be able to accept new rules.
Same, if they want to accept new rules they need to update their sw, if they donât want to accept these rules they just remain on the same version and when the fork takes place their nodes will fork from the updated ones.
1 Like
A fork means there are multiple (at least 2) blocks that have been found at the same height and are both valid
When the longest chain is eventually found the blocks from the shortest chain will be discarded and the tx from those blocks returned to the mempool.
Thank you! 
I have a couple last questions: if someone had 10 btc at the time the fork happened, will this person have 10 btc and 10 of the new coin? Which means that the person has more money because they have 10 coins in different blockchains?
Yes in case of a hard fork two blockchains occur with the same history of txs.
1 Like