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index.js
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index.js
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const sha256 = require("crypto-js/sha256");
const EC = require("elliptic").ec;
var ec = new EC("secp256k1");
class Block{
constructor(timestamp, transactions, previousHash = ""){
this.timestamp = timestamp;
this.transactions = transactions;
this.previousHash = previousHash;
this.hash = this.calcualteHash();
this.nonce = 0;
}
mineBlock(difficulty){
while(this.hash.substring(0, difficulty) !== Array(difficulty+1).join("0")){
this.nonce++;
this.hash = this.calcualteHash();
}
console.log("Mining done : "+this.hash);
}
calcualteHash(){
return sha256(
this.timestamp + JSON.stringify(this.transactions) + this.previousHash+this.nonce
).toString();
}
hasValidTransactions(){
for(const tx of this.transactions){
if(!tx.isValid())
return false;
}
return true;
}
}
class Transaction{
constructor(fromAddress, toAddress, amount){
this.fromAddress = fromAddress;
this.toAddress = toAddress;
this.amount = amount;
}
calcualteHash(){
return sha256(this.fromAddress+this.toAddress+this.amount).toString();
}
signTransaction(key){
if(key.getPublic("hex") !== this.fromAddress)
throw new Error("You do not have access");
const hashTx = this.calcualteHash();
const signature = key.sign(hashTx, "base64");
this.signature = signature.toDER();
}
isValid(){
if(this.fromAddress === null) true;
if(!this.signature || this.signature.length === 0)
throw new Error("No signature found.");
const key = ec.keyFromPublic(this.fromAddress, "hex");
return key.verify(this.calcualteHash(), this.signature);
}
}
class Blockchain{
constructor(){
this.chain = [this.genesisBlock()];
this.difficulty = 3;
this.pendingTansactions = [];
this.miningReward = 50;
}
genesisBlock(){
return new Block("2019-01-01", "GENESIS", "0000");
}
getLatestBlock(){
return this.chain[this.chain.length-1];
}
addTransaction(transaction){
if(!transaction.fromAddress || !transaction.toAddress)
throw new Error("Cannot process transaction");
if(!transaction.isValid())
throw new Error("Invalid transaction");
if(transaction.amount < 0)
throw new Error("Invalid transaction amount");
// if(transaction.amount > this.getBalanceOfAddress(transaction.fromAddress))
// throw new Error("Not enough balance");
this.pendingTansactions.push(transaction);
}
minePendingTransactions(minerAddress){
let block = new Block(Date.now(), this.pendingTansactions);
block.mineBlock(this.difficulty);
this.chain.push(block);
this.pendingTansactions = [
new Transaction(null, minerAddress, this.miningReward)
];
}
isBlockchainValid(){
for(let i = 1; i < this.chain.length; i++){
const currentBlock = this.chain[i];
const previousBlock = this.chain[i-1];
if(currentBlock.hash !== currentBlock.calcualteHash()){
return false;
}
if(currentBlock.previousHash !== previousBlock.hash){
return false;
}
if(!currentBlock.hasValidTransactions())
return false;
}
return true;
}
getBalanceOfAddress(address){
let balance = 0;
for(const block of this.chain){
for(const trans of block.transactions){
if(trans.fromAddress === address){
balance-=trans.amount;
}
if(trans.toAddress === address){
balance+=trans.amount;
}
}
}
return balance;
}
}
module.exports = {
Block,
Transaction,
Blockchain
}