What does Double Spending mean?
Double spending or double issues involve the resale of the same assets. We usually talk about electronic payment systems that have the inherent ability to copy states, allowing you to make multiple payments from the same initial state.
Double Spending based on the blockchain
In decentralized payment systems, such as cryptocurrencies, there is no controlling body. In order to avoid duplication, it has been proposed to group transactions into blocks that are embedded in continuous chains.
To get the right to add a block, you need to demonstrate the proof-of-work. By checking the chain, you can make sure that the same “electronic coin” has not been previously issued.
Proof-of-stake versus proof-of-work
In fact, the transaction authenticates the node that it comprises in the block. All other transactions with the same “electronic coin” and the same owner are now ignored by the system.
Later, regulations were proposed to use the proof-of-stake shareholdings instead of the proof-of-work. The main objective of the construction of the block is to provide a criterion for reaching a consensus on which version of transactions is considered correct.
The system is secure as long as most of its computing resources are under the control of honest subscribers.
The information in the blockchain is open to all. However, the counterparties can only verify the existence of the sender's assets.
If several payments that transmit the same asset are running fast enough, information about them will not get confirmation (they will not come in the next block or will not be legitimated otherwise) and each of the recipients of the legitimacy of its transactions will be secure.
Only after one of the transactions, which is not necessarily completed first, is it confirmed that the remaining transactions are no longer valid with the same asset.