README.md

How to Work BlockChain

how to work blockchain, this is only example structure. 😃

small tutorial with code to try to create your blockchain.

I used typescript because is very easy to read/understand.

---

Block.ts

Instance variable

• index ===> index block.

• timestamp ===> date of block instance.

• data ===> any type of data to save in block

• precedentHash ===>hash of the last block (lock added before this block).

• hashBlock ===> hash of this block.

• nonce ===>it has nothing to do with blocking, change to something random (example random number).

constructor block

public constructor(index,data)

methods of the block.

 public getHashBlock();
 
 public getprecedentHash();

 public setPrecedentHash(hash);
 
 public  generateHash();
 

Proof-of-work is used to make secure the blockchain(similar bitcoin Hashcash)

more info https://en.wikipedia.org/wiki/Proof-of-work_system

public mineBlock(miningDifficulty:number){
    while(this.hashBlock.substring(0,miningDifficulty)!=Array(miningDifficulty+1).join('0')){
      this.nonce++;
      this.generateHash();
  }

---

BlockChain.ts

Instance variable

• chain:Array ===> array of block,(better chained list).
• miningDifficulty ===> the difficulty of mining expressed in numbers(the more the number is high the more the difficulty increases).

constructor BlockChain

as a parameter it takes the difficulty of mining. when to start the blockchain, add the first block (this block is without the previous hash block because is the first block)

constructor(miningD){
 this.chain=new Array<Block>(new Block(0,{ firstBlock:"Created By Aymen Naghmouchi"}));
 this.miningDifficulty=miningD;
}

methods of the BlockChain.

  public getLastBlock();
  
  public checkBlockChain();
  

set the precedent block hash in the last added and regenerate her hash

 public addBlock(newBlock){
   newBlock.setPrecedentHash(this.getLastBlock().getHashBlock());
   newBlock.mineBlock(this.miningDifficulty);
   this.chain.push(newBlock);
  }

check all blocks are linked among them.

  public checkBlockChain():boolean{
    for(let i:number=1;i<this.chain.length;i++){
      let actualblock:Block=this.chain[i];
      let precedentblock:Block=this.chain[i-1];
      if(actualblock.getPrecedentHash()!==precedentblock.getHashBlock())
        return false;
    }
    return true;
  }

OUTPUT

{
  "chain": [
    {
      "index": 0,
      "timestamp": "2018-01-21T14:23:12.424Z",
      "data": {
        "firstBlock": "Created By Aymen Naghmouchi"
      },
      "hashBlock": "47234aa1697b3fd20bc5db17b899ac0d1d6adc7608cbca7fbdcd515d89c81954",
      "nonce": 0
    },
    {
      "index": 1,
      "timestamp": "2018-01-21T14:23:12.428Z",
      "data": {
        "user": "Aymen Naghmouchi",
        "Amount": 100
      },
      "hashBlock": "0008d50dfd76575392335a0df6b82d52826c75ee827b0c639c77405dc40b22cc",
      "nonce": 4636,
      "precedentHash": "47234aa1697b3fd20bc5db17b899ac0d1d6adc7608cbca7fbdcd515d89c81954"
    },
    {
      "index": 2,
      "timestamp": "2018-01-21T14:23:12.515Z",
      "data": {
        "user": "Aymen Naghmouchi",
        "Amount": 2500
      },
      "hashBlock": "0000c505fb52117656109daff8c9d18325b782b9674eb6f0d64840de43f0f0cc",
      "nonce": 4302,
      "precedentHash": "0008d50dfd76575392335a0df6b82d52826c75ee827b0c639c77405dc40b22cc"
    },
    {
      "index": 3,
      "timestamp": "2018-01-21T14:23:12.566Z",
      "data": {
        "user": "Aymen Naghmouchi",
        "Amount": 50
      },
      "hashBlock": "000fd901ae1c2622cb9b48a801099d8f5c884d73b86402078cdf9eea78c787eb",
      "nonce": 1479,
      "precedentHash": "0000c505fb52117656109daff8c9d18325b782b9674eb6f0d64840de43f0f0cc"
    }
  ],
  "miningDifficulty": 3
}
all blocks are linked? true

How to use

• git clone or fork it
• npm install
• npm start

compile

tsc main.ts

execute

node main.js