Nonce

• Only blocks whose hashes start with a certain number of 0’s can be added to the ledger. Why?

• The idea is to create competition among the miner. Who will find the number that will contain a run of leading zeros below the difficulty target first. Remember the SHA256 hash is unpredictable.

• Thus, the miners has to add an arbitrary number to the block, known as nonce (i.e. 9876879).

• Finding the a block with a certain number of 0’s is a brute force task, and can only be achieved by testing different combinations as fast as possible (lots of random guesses/trail and error – which keeps it fair).

• Hash value is unique for the combination of a nonce and input date

• The guessing game is called ‘hashing’.