Browser crypto.subtle (SubtleCrypto) simple encrypt/decrypt

gistfile1.js

// derive string key
async function deriveKey(password) {
  const algo = {
    name: 'PBKDF2',
    hash: 'SHA-256',
    salt: new TextEncoder().encode('a-unique-salt'),
    iterations: 1000
  }
  return crypto.subtle.deriveKey(
    algo,
    await crypto.subtle.importKey(
      'raw',
      new TextEncoder().encode(password),
      {
        name: algo.name
      },
      false,
      ['deriveKey']
    ),
    {
      name: 'AES-GCM',
      length: 256
    },
    false,
    ['encrypt', 'decrypt']
  )
}

// Encrypt function
async function encrypt(text, password) {
  const algo = {
    name: 'AES-GCM',
    length: 256,
    iv: crypto.getRandomValues(new Uint8Array(12))
  }
  return {
    cipherText: await crypto.subtle.encrypt(
      algo,
      await deriveKey(password, algo.name, algo.length),
      new TextEncoder().encode(text)
    ),
    iv: algo.iv
  }
}

// Decrypt function
async function decrypt(encrypted, password) {
  const algo = {
    name: 'AES-GCM',
    length: 256,
    iv: encrypted.iv
  }
  return new TextDecoder().decode(
    await crypto.subtle.decrypt(
      algo,
      await deriveKey(password, algo.name, algo.length),
      encrypted.cipherText
    )
  )
}

// example
;(async () => {
  // encrypt
  const encrypted = await encrypt('Secret text', 'password')

  // the cipher text
  console.log(
    String.fromCharCode.apply(null, new Uint8Array(encrypted.cipherText))
  )

  // decrypt it
  const decrypted = await decrypt(encrypted, 'password')
  console.log(decrypted) // Secret text
})()