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In Bitcoin blockchain, Segwit takes the script, which containers the signature and sender's public key, out of each transaction and stores them into an extended block. However, why having an extended block can make the blockchain faster? Since I think each miner now has to process the original block plus the extended block, thus the amount of data each miner needs to be processed has not been changed. Please advise!
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First of all, your understanding of segwit is incorrect. There is not extended block, the witness data is still part of the transaction.
Segwit also does not "make the blockchain faster". What part of it does is it redefines the maximum block size metric to be something called block weight. Witness data is weighted differently from non-witness data, which means that a block containing witness data will have more spare weight units to contain more transactions. This means that Bitcoin's transaction capacity will increase, as will the size of blocks.
It may be worth pointing out that while it doesn't make anything faster, it very intentionally does not make the worst case validation time much worse (i.e. the worst case per transaction is faster with than without). – Pieter Wuille – 2017-08-26T20:05:45.157
If Segwit does not "make to blockchain faster", what is the benefit of Segwit? In other words, what 's the benefit of increasing Bitcoin's transaction capacity? – Qi Zhang – 2017-08-27T14:49:47.043
It means that more transactions can fit in a block, which means that more transactions can be confirmed at once. This does not make anything faster; it makes Bitcoin able to confirm more transactions simultaneously. – Andrew Chow – 2017-08-27T15:05:02.200
I see, but why can't we say that confirming more transactions at once essentially makes the Bitcoin blockchain faster?@AndrewChow – Qi Zhang – 2017-08-27T20:28:17.797
Because the blockchain a) has no speed and b) nothing is getting faster. – Andrew Chow – 2017-08-27T20:28:52.980