native-browser-otp/dist/native-browser-otp.es.js

Lightweight library for generating TOTP and HOTP codes using browser's native Web Cryptography API. Perfect for implementing two-factor authentication (2FA) in web applications.

import decode from "base32-decode";
async function createHmac(secret, text) {
  const key = await crypto.subtle.importKey(
    "raw",
    decode(secret, "RFC4648"),
    { name: "HMAC", hash: { name: "SHA-1" } },
    false,
    ["sign", "verify"]
  );
  const hash = await crypto.subtle.sign("HMAC", key, text);
  return new Uint8Array(hash);
}
function truncate(hash) {
  const offset = hash[hash.length - 1] & 15;
  return (hash[offset] & 127) << 24 | (hash[offset + 1] & 255) << 16 | (hash[offset + 2] & 255) << 8 | hash[offset + 3] & 255;
}
async function hotp(secret, counter) {
  const text = new Uint8Array(8);
  for (let i = text.length - 1; i >= 0; i--) {
    text[i] = counter & 255;
    counter >>= 8;
  }
  const hash = await createHmac(secret, new Uint8Array(text));
  const binary = truncate(hash);
  const otp = binary % 1e6;
  return String(otp).padStart(6, "0");
}
async function totp(secret) {
  const code = await hotp(secret, Math.floor(Date.now() / 3e4));
  return code;
}
function timeLeft() {
  return 30 - Math.floor(Date.now() / 1e3) % 30;
}
export { hotp, timeLeft, totp };