Hi everyone! I would like to ask something about the videos.
How is it possible to Bob to create a different and still valid signature? It is not supposed that only Alice can create that signature, since only she has got the private keys?
Thank you in advance! <3
Bob changes the unlocking script or the witness which consequently changes the tx hash, it doesnât change Alices signature.
You can learn about this in detail in our Bitcoin programming course. 
Thanks! Fore sure I will try to go for deeper understanding of this 
Given all the complexities involved, Segwit was an ingenious way of avoiding a Hard Fork, improving the Bitcoin network and maintaining network/coin value. In my opinion, maintaining the original network as much as possible has an intangible value that is embedded in todayâs price. What that exact amount is? I really canât say, but when an average investor comes to make a decision Iâm betting that the original coin is where he leans to because it is (in his consideration) the real one.
The Segwit solution, in my opinion, was the best solution. Given the expansion to layer 2 programming (smart protocols) and the implementation of Segwit, it deserves a lot of respect to the time and effort that the community invested in maintaining the current highest performing asset class.
From the solution of the initial issue (Block size) to the solution of other network flaws (Transaction Malleability), Segwit has maintained the Bitcoin Network for its current advancement and our global digital asset adoption. If not for maintaining Bitcoinâs dominance, all other digital assets (coins, tokens, NFTs, etc) would not be a casual conversation to date.
Filip,
Iâm confused about Bob being able to alter the signature from Alice?
I thought that a transaction signature is encrypted and thus not able to be altered?
I learnt a lot, thank you Filip.
Hi,
How are you?
How can a block be full?
How many can you make blocks or blockchain?
Thankâs
B
I donât know why the quiz on segwit isnât working. Is there a problem with the system?
Hey @Sieg_Kamgo, hope you are ok.
Could you please detail why is not working for you? maybe an screenshot of the error you are facing
Carlos Z
was it before segwit possible to alter a TX, or was that more a theory?
So segwit is a softfork but isnât a softfork suppose to be undemocratic.
Hi @filip, how can a transaction be modified by someone other than the sender (since only the sender has access to the private key upon which the digital signature is based)?
The receiver was able to modify the unlocking script or the witness part of the tx. Which is responsible to unlock the funds for the next tx. If he managed to do that when the tx was still in the mempool the txid.
This malleability is still present on chains like BCH and BSV.
I think that technically soft forks are more democratic. Because it is the vote of the majority that gets accepted and the minority has to follow the new rule that was accepted while in hardfork both can just follow the new rule. So Iâm not sure why it is thought hard forks are more democratic 
In any case you donât need to follow Segwit because old style txs are still valid on Bitcoin.
You state what is happening but I do not understand how it all technically works.Could you please explain how he technically changes a signature etc?How does Bob and Alice technically/manually do what they do in the example.
Let say Alice sends 10 BTC to Bob and Alice broadcasts a request to the network, the transaction malleability flaw in Bitcoinâs code allows Bob to change Aliceâs witness data before the transaction is confirmed. This changes the transaction ID without changing the transaction itself (which is still 10BTC being sent from Alice to Bob). When this altered transaction is confirmed by the network, it cancels out the original transaction. Now Bob contacts Alice to complain that he hasnât received 10BTC, even though he has! Alice checks and sees that the original transaction hasnât gone through. She now attaches a higher transaction fee and sends it again. This new transaction is processed by the network. Bob receives 10 more Bitcoins.
You can learn about this in detail in our Bitcoin programming course.
Ok thanks I will go do the Bitcoin programming course.
@filip
In the lecture on forks you stated that with a soft fork, once over 50% of the nodes update to the new set of Consensus Rules the updated fork will become longer and show more PoW. Once this happens the old fork would drop off and its transactions would go back to the mempool and we would be left with only the updated fork. Just like it does with accidental forks. You mentioned it as âmajority ruleâ when you talked about the pros and cons of Soft Forks and Hard Forks. So how is it possible that over 50% of nodes have done the Segwit update yet the original fork is permitted to go on? Shouldnât it have dropped off and its transactions gone back to the mempool since it now has less PoW and the network will always choose the fork with more PoW?
95 percent of the networkâs miners would have the span of two weeks (2,016 blocks; aka a difficulty period) to begin mining SegWit blocks. If 95 percent of hashing power generated blocks under the new SegWit rules within this timeframe, then the soft forkâs rules would be âlocked inâ to the network and would be fully activated.
Filip said in the lecture that it was only 50% required to cause the old fork to drop off. He also didnât give a time frame. Is Segwit an exception that required 95%?