Web Cryptography APIWeb Cryptography API

const subtle = window.crypto.subtle;

// 1. 해시 (SHA-256)
async function hash(message) {
  const encoder = new TextEncoder();
  const data = encoder.encode(message);
  const hashBuffer = await subtle.digest('SHA-256', data);
  return Array.from(new Uint8Array(hashBuffer))
    .map(b => b.toString(16).padStart(2, '0'))
    .join('');
}
const h = await hash('Hello, World!');  // 'dffd...'

// 2. AES-GCM 대칭 암호화
async function encryptAES(plaintext, key) {
  const iv = crypto.getRandomValues(new Uint8Array(12));  // 96비트 IV
  const encoded = new TextEncoder().encode(plaintext);
  const ciphertext = await subtle.encrypt(
    { name: 'AES-GCM', iv },
    key,
    encoded
  );
  return { iv, ciphertext };
}

// 키 생성
const aesKey = await subtle.generateKey(
  { name: 'AES-GCM', length: 256 },
  true,   // extractable
  ['encrypt', 'decrypt']
);

// RSA-OAEP 키 쌍 생성
const { publicKey, privateKey } = await subtle.generateKey({
  name: 'RSA-OAEP',
  modulusLength: 2048,
  publicExponent: new Uint8Array([0x01, 0x00, 0x01]),  // 65537
  hash: 'SHA-256'
}, true, ['encrypt', 'decrypt']);

// 암호화 (공개 키)
const encrypted = await subtle.encrypt(
  { name: 'RSA-OAEP' },
  publicKey,
  new TextEncoder().encode('secret message')
);

// 복호화 (개인 키)
const decrypted = await subtle.decrypt(
  { name: 'RSA-OAEP' },
  privateKey,
  encrypted
);
console.log(new TextDecoder().decode(decrypted));

// ECDSA 키 쌍
const { publicKey, privateKey } = await subtle.generateKey(
  { name: 'ECDSA', namedCurve: 'P-384' },
  true,
  ['sign', 'verify']
);

const data = new TextEncoder().encode('서명할 데이터');

// 서명
const signature = await subtle.sign(
  { name: 'ECDSA', hash: 'SHA-384' },
  privateKey,
  data
);

// 검증
const valid = await subtle.verify(
  { name: 'ECDSA', hash: 'SHA-384' },
  publicKey,
  signature,
  data
);
console.log(valid);  // true

// 키 내보내기/가져오기
const exported = await subtle.exportKey('jwk', publicKey);
const imported = await subtle.importKey('jwk', exported,
  { name: 'ECDSA', namedCurve: 'P-384' }, true, ['verify']);