OTPAuth

One Time Password library for Node.js, Deno, Bun and browsers.

It supports the generation and validation of
HMAC-Based One-Time Passwords (HOTP) as specified in RFC 4226 and
Time-Based One-Time Passwords (TOTP) as specified in RFC 6238.
Frequently used in Multi-Factor Authentication (MFA) / Two-Factor Authentication (2FA) systems.

> [!TIP]
> You can try the library with the demo application available at otpauth.molinero.dev.
>
> If you wish to interact with the library in your browser console, the following snippet can be used:
>
> ``javascript
> const OTPAuth = await import("otpauth");
> `

Usage

This section presents an overview of the most common usage patterns, along with some security recommendations.

$3

`javascript
import * as OTPAuth from "otpauth";
// import * as OTPAuth from "otpauth/slim"; // Slim build without bundled dependencies.
// import * as OTPAuth from "otpauth/bare"; // Bare build with no bundled crypto (requires providing a custom HMAC function).

// Create a new TOTP object.
let totp = new OTPAuth.TOTP({
// Provider or service the account is associated with.
issuer: "ACME",
// Account identifier.
label: "Alice",
// Algorithm used for the HMAC function, possible values are:
// "SHA1", "SHA224", "SHA256", "SHA384", "SHA512",
// "SHA3-224", "SHA3-256", "SHA3-384" and "SHA3-512".
algorithm: "SHA1",
// Length of the generated tokens.
digits: 6,
// Interval of time for which a token is valid, in seconds.
period: 30,
// Arbitrary key encoded in base32 or OTPAuth.Secret instance
// (if omitted, a cryptographically secure random secret is generated).
secret: "US3WHSG7X5KAPV27VANWKQHF3SH3HULL",
// or: OTPAuth.Secret.fromBase32("US3WHSG7X5KAPV27VANWKQHF3SH3HULL")
// or: new OTPAuth.Secret()
// Custom HMAC function (required for bare build, optional otherwise).
// hmac: (algorithm, key, message) => Uint8Array,
});

// Unless you know what you are doing, it is recommended to use the default
// values for the algorithm, digits, and period options, as these are the most
// common values used by most services.

// Generate a cryptographically secure random secret.
// It is NOT recommended to use less than 128 bits (16 bytes).
let secret = new OTPAuth.Secret({ size: 20 });

// Generate a token (returns the current token as a string).
let token = totp.generate();

// Validate a token (returns the token delta or null if it is not found in the
// search window, in which case it should be considered invalid).
//
// A search window is useful to account for clock drift between the client and
// server; however, it should be kept as small as possible to prevent brute
// force attacks. In most cases, a value of 1 is sufficient. Furthermore, it is
// essential to implement a throttling mechanism on the server.
//
// For further details on the security considerations, it is advised to refer
// to Section 7 of RFC 4226 and Section 5 of RFC 6238:
// https://datatracker.ietf.org/doc/html/rfc4226#section-7
// https://datatracker.ietf.org/doc/html/rfc6238#section-5
let delta = totp.validate({ token, window: 1 });

// Get the counter value (number of intervals since the Unix epoch).
// Useful for implementing techniques against token reuse during the validity
// period.
let counter = totp.counter();

// Get the remaining milliseconds until the current token changes.
let remaining = totp.remaining();

// Convert to Google Authenticator key URI format.
// Usually the URI is encoded in a QR code that can be scanned by the user.
// This functionality is outside the scope of the project, but there are many
// libraries that can be used for this purpose, such as npmjs.com/package/qr
let uri = totp.toString();
// or: OTPAuth.URI.stringify(totp)
// returns: otpauth://totp/ACME:Alice?issuer=ACME&secret=US3WHSG7X5KAPV27VANWKQHF3SH3HULL&algorithm=SHA1&digits=6&period=30

// Convert from Google Authenticator key URI format.
totp = OTPAuth.URI.parse(uri);
`

$3

`javascript
import * as OTPAuth from "jsr:@hectorm/otpauth";

// Same as above.
`

$3

`html


`

$3

`html
src="https://cdn.jsdelivr.net/npm/otpauth@%VERSION%/dist/otpauth.umd.min.js"
integrity="%HASH%"
crossorigin="anonymous"
referrerpolicy="no-referrer"
>

``

Documentation

For additional information, please refer to the documentation page at hectorm.github.io/otpauth/.

License

MIT License
© Héctor Molinero Fernández.