Cryptocurrency

Bitcoin, Ethereum, transaction mechanics, wallets, and digital signatures.

Overview

Cryptocurrency is digital currency secured by cryptography.

Bitcoin Transaction

{
  "txid": "abc123...",
  "inputs": [
    {
      "prevTx": "def456...",
      "outputIndex": 0,
      "scriptSig": "signature..."
    }
  ],
  "outputs": [
    {
      "value": 0.5,
      "scriptPubKey": "address..."
    }
  ]
}

Wallet Types

Ethereum Accounts

// EOA (Externally Owned Account)
const account = {
  address: "0x1234...",
  balance: "1.5", // ETH
  nonce: 42,
  privateKey: "0x..."
};

// Contract Account
const contract = {
  address: "0x5678...",
  balance: "10.0",
  code: "0x606060...",
  storage: {}
};

Gas Fees

// Gas calculation
const gasLimit = 21000;
const gasPrice = "20"; // Gwei

const totalFee = gasLimit * gasPrice;
// Total in ETH = totalFee * 10^-18

Mining Rewards

Bitcoin Halving Schedule:
2009: 50 BTC
2012: 25 BTC
2016: 12.5 BTC
2020: 6.25 BTC
2024: 3.125 BTC

Practice

Create a simple cryptocurrency wallet application.