The ledger module is the data hub of the blockchain. The balances and transactions of all accounts are saved in the ledger module.
A network-wide account book is saved on each network node to ensure complete, open and transparent data, while ensuring that data cannot be tampered and traceable.
Provide data support for assembly transactions, mainly accounting and auditing, verify the legality of the transaction, such as: whether there is sufficient balance, whether to repeat payment (double flower)
The ledger module is the data hub, which stores the result data of all existing transactions in the system. It does not depend on any business modules, and other modules depend on it as needed.
Explanation of nouns in ##《本本模块》
The random number of the transaction (nonce, the last 8 bytes of the transaction hash value)
nonce: A scalar value equal to the number of transactions sent at this address, which will be included in every transaction initiated by the user.
Each transaction in the account needs to save the previous nonce of the transaction.
Strictly speaking, a nonce is an attribute of the originating address (it only makes sense in the context of the sending address).However, the nonce is not explicitly stored in the blockchain as part of the account status.
The nonce value is also used to prevent incorrect calculation of account balances.For example, suppose an account has 10 NULS balances and signs two transactions, all of which cost 6 NULS with nonce 1 and nonce 2, respectively.Which of these two transactions is valid? In a blockchain distributed system, nodes may receive transactions out of order.Nonce forces transactions of any address to be processed in order, regardless of the interval, regardless of the order in which the nodes receive.This way, all nodes will calculate the same balance.Payments for 6 Ethereum will be processed successfully and the account balance will be reduced to 4 ether.Whenever it is received, all nodes consider it invalid with a transaction with nonce 2.If a node receives a nonce 2 transaction first, it will hold it, but will not commit it until it receives and processes the nonce 1 transaction.
Use nonce to ensure that all nodes calculate the same balance and sort the transactions correctly, which is equivalent to the mechanism used in Bitcoin to prevent "double payment".However, because Ethereum tracks account balances and does not track individual coins separately (called UTXO in Bitcoin), "double payments" only occur when the account balance is incorrectly calculated.The nonce mechanism can prevent this from happening.
