Konsep Dasar Blockchain

Blockchain adalah teknologi Distributed Ledger yang terdiri dari serangkaian block yang terhubung secara kriptografis dengan algoritma SHA256. Dalam simulator ini setiap block mengandung:

• Data Transaksi: Informasi yang dicatat (input pengguna)
• Hash Saat ini: Digital fingerprint unik dihasilkan dari SHA256(block content)
• Hash Sebelumnya: Tautan kriptografis ke block sebelumnya (basis keamanan rantai)
• Timestamp: Waktu pencatatan transaksi (terenkripsi UNIX timestamp)

Karakteristik Utama

Arsitektur Sistem

1. Class Block

					class Block {
						constructor(index, timestamp, data, previousHash) {
							this.index = index;
							this.timestamp = timestamp;
							this.data = data;
							this.previousHash = previousHash;
							this.hash = this.calculateHash();
						}
						
						calculateHash() {
							return CryptoJS.SHA256(
								this.index +
								this.previousHash +
								this.timestamp +
								JSON.stringify(this.data)
							).toString(CryptoJS.enc.Hex);
						}
					}
				

2. Class Blockchain

					class Blockchain {
						constructor() {
							this.chain = [this.createGenesisBlock()];
						}
						
						createGenesisBlock() {
							return new Block(
								0, 
								new Date().toISOString(), 
								{ data: 'Genesis Block' }, 
								'0000000000000000000000000000000000000000000000000000000000000000'
							);
						}
						
						getLatestBlock() {
							return this.chain[this.chain.length - 1];
						}
						
						addBlock(newBlock) {
							if (this.validateNewBlock(newBlock)) {
								this.chain.push(newBlock);
								return true;
							}
							return false;
						}
						
						validateNewBlock(newBlock) {
							const lastBlock = this.getLatestBlock();
							const expectedHash = CryptoJS.SHA256(
								newBlock.index +
								newBlock.previousHash +
								newBlock.timestamp +
								JSON.stringify(newBlock.data)
							).toString(CryptoJS.enc.Hex);
							
							return (
								newBlock.index === lastBlock.index + 1 &&
								newBlock.previousHash === lastBlock.hash &&
								newBlock.hash === expectedHash
							);
						}
						
						isChainValid() {
							for (let i = 1; i < this.chain.length; i++) {
								const current = this.chain[i];
								const previous = this.chain[i - 1];
								
								if (current.hash !== current.calculateHash()) return false;
								if (current.previousHash !== previous.hash) return false;
							}
							return true;
						}
					}
				

Mekanisme Hashing SHA-256

				// Contoh penggunaan SHA-256
				const hash = CryptoJS.SHA256('Contoh data').toString(CryptoJS.enc.Hex);
				// Hasil: 'a3f4c5d6...' (64 karakter hexadesimal)