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Nonce

Nonce is an arbitrary number which enters the block header. When creating a block, it is necessary for the block to continuously input random values until the hash of the block becomes equal to or lower than the target. The peculiarity of the hash function is that if the input value is constant, the result value is always constant. In the block header, all value excluding the nonce is fixed, thus the hashing in this condition will derive the same results every time.

So, the hash result can be adjusted by inputting nonce, the arbitrary number, orderly until obtaining the desired hash value.

The miner of the block #563215 discovers the hash, which is smaller than the target value, by inputting 3269250953 to the nonce.

Ethereum, which adopts PoW consensus algorithm like Bitcoin, also uses nonce as for the value to put into the block header. And nonce is also used as a kind of counter to allow a transaction to be processed only once in an account. It stands for the number of transactions sent out to the account in EOA(Externally Owned Accounts), and the number of contracts created by the account in CA(Contract Accounts).