How is a block mined?

1. Look at the latest block on the blockchain

2. Get the Index and increment by 1

3. Get the latest block's hash and store as previous hash

4. Create data

5. Calculate Hash

6. Calculate Nonce

Demo

https://blockchaindemo.io/

Proof of work

• Not just any hash value is valid.

• A valid hash has to pass a requirement, called Difficulty.

Difficulty

• This is the minimum requirement for a valid hash.

• A valid hash has at least four leading 0’s. (demo)

function isValidHashDifficulty(hash, difficulty) {
  for (var i = 0, b = hash.length; i < b; i ++) {
      if (hash[i] !== '0') {
          break;
      }
  }
  return i >= difficulty;
}

What is a nonce?

• Number of iterations used to find a valid hash

• This process is called mining

let nonce = 0;
let hash;
let input;

while(!isValidHashDifficulty(hash)) {     
  nonce = nonce + 1;
  input = index + previousHash + timestamp + data + nonce;
  hash = CryptoJS.SHA256(input)
}