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Hello I'm the student studying blockchain and bitcoin.

I have a question that why all node verify all transactions in blocks.

I check if new node connect bitcoin network, then the all transactions in blocks are verified.

The transactions before connecting new node are already verified, but why new node check all transactions in blocks???

I feel that "new node doesn't check previous transactions" have some problems, but clear idea doesn't know.

Please tell me why. ㅠ.ㅠ

2 Answers 2

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Bitcoin is designed to work in an antagonistic environment. If our node trusts what other nodes tell it blindly, it is trivial to lie to it. Instead, our node processes the complete blockchain itself and checks that all rules were adhered to. This way, it cannot fall for invalid transaction or block data.

More generally, since there is no single leader or decider, the network needs a mechanism how to converge on a single ground truth. If every node believed everything other nodes told it, it would be probably easy to split the network, waste bandwidth, and delay or prevent convergence. Making it costly to produce the canonical truth and everyone checking its validity inundates the network against many of these attacks.

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  • What happen in that case?? I want to know precise situation
    – hhhbbb
    Oct 26, 2021 at 12:05
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    Fore example my node tells you that I have 1,000 BTC and then pays you from that 1,000 BTC. You give me some other good for my payment, but then realize that the bitcoins don't actually exist.
    – Murch
    Oct 26, 2021 at 15:16
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why all node verify all transactions in blocks.

So that they don't have to trust anyone else.

This way each node knows for certain which "coins" are already spent and thereby avoid fraud.

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