AES 思想与可运行的分组/流密码

// 运行环境：Node.js 14+
// 保存为 aj-l14.js，执行：node aj-l14.js
const crypto = require('crypto')

// 1) XOR 流密码：密钥流 = 由种子派生的伪随机字节
function xorStream(plaintext, key) {
  const keyBytes = Buffer.from(key)
  const out = Buffer.alloc(plaintext.length)
  for (let i = 0; i < plaintext.length; i++) {
    out[i] = plaintext[i] ^ keyBytes[i % keyBytes.length] // 逐字节异或
  }
  return out
}
const msg = Buffer.from('secret message')
const enc = xorStream(msg, 'mykey')
const dec = xorStream(enc, 'mykey') // 异或两次还原
console.log('密文:', enc.toString('hex'))
console.log('还原:', dec.toString()) // secret message

// 2) 直接用 Node 内置 AES（生产请用这个，别自己造轮子）
function aesDemo(plaintext, key32) {
  const iv = crypto.randomBytes(16)
  const cipher = crypto.createCipheriv('aes-256-cbc', key32, iv)
  const enc = Buffer.concat([cipher.update(plaintext), cipher.final()])
  return iv.toString('hex') + ':' + enc.toString('hex')
}
console.log('AES-256-CBC:', aesDemo(Buffer.from('hello'), crypto.randomBytes(32)))