Prevention strategy of Chang'an chain Shuanghua transaction

What is double flower transaction

        That is, a sum of money is spent twice or more , Also called “ Double pay ”. In the digital money system , Due to the replicability of data , This makes it possible that the same digital asset may be reused due to improper operation .

How to solve bitcoin “ Two flowers ” problem

        Bitcoin as a decentralized point-to-point e-cash system , It mainly depends on the transaction output that is not spent （unspend transaction output, UTXO） And timestamp “ Two flowers ” problem .

        The system uses digital timestamp to ensure that each block is connected into a blockchain in chronological order , The timestamp also marks the time of every data on the blockchain .

        Suppose Xiao Ming will exist in himself UTXO Medium 1 individual BTC At the same time, transfer money to Li Lei and Han Meimei , Only one of the two transactions will be successfully completed . Why? ？ Because the node in the system will selectively record the transaction received first . When two transactions are recorded by the same node at the same time , According to the timestamp data , Only the transactions recorded first can be confirmed to be successful .

        If Xiao Ming's two transfers are very, very close ,“ Xiao Ming is in 12 spot 34 branch 56 Seconds to Li Lei 1 Bitcoin ”、“ Xiao Ming is in 12 spot 34 branch 57 Second to Hanmeimei 1 Bitcoin ” It happens to be recorded by two different nodes , There will be “ Two flowers ” Do you ？ Not even . These two nodes will broadcast their respective blocks containing related transactions to the bitcoin network at the same time , At this point, the blockchain will fork , The remaining nodes choose to build new blocks on what they think is the longest chain . Last , Take the lead in building a new block and become the transaction on the longest chain （ Usually it is 6 Block ）, Can be confirmed to be successful . All subsequent nodes will build new blocks on this longest chain .

To sum up , face “ Double flower problem ”, Bitcoin cash system is solved in this way ：

    First , Each transaction must first confirm the situation before the corresponding bitcoin , Check whether it exists in Xiaoming's UTXO in . If not , Then the transaction will be rejected by the system .
    If Xiao Ming uses the same pen UTXO Pay Li Lei and Han Meimei , The node in the system only confirms the one received first .