Electronic transactions
First of all, within the paper, a coin (the original concept of Bitcoin) is defined as a chain-like sequence of electronic signatures.
The owner of the coin combines the following data when sending the coin
- All previous transaction information, including the information he is sending.
- The public key of the recipient.
In addition, the entire data is hashed, and finally digitally signed.
This data is then added to the end of the digital currency and sent to the sender in bulk.
The important thing here is that all the transaction details and the digital signature are included in the set.
In this way, it is possible to verify who has owned the coin so far.
However, as it is, it is not possible to check whether the coin has been used for multiple payments in the past.
Until now, financial institutions have existed to solve this very problem, but the mechanism in the paper solves this problem by setting the following rules.
"If a coin is used for multiple payments, only the first transaction is valid, the second and subsequent ones are invalid."
This further raises the issue that there is no way to verify which transaction is the first one.
To address this, he explains that all transactions can be confirmed by making them available to everyone, including those not involved in the transaction, and having everyone share the same transaction history.
In other words, if everyone shares the same history, they can all agree on which was the first transaction.
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