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A library for performing FIDO 2.0 / WebAuthn server functionality

This library contains all the functionality necessary for implementing a full FIDO2 / WebAuthn server. It intentionally does not implement any kind of networking protocol (e.g. - REST endpoints) so that it can remain independent of any messaging protocols.

There are four primary functions:

  1. attestationOptions - creates the challenge that will be sent to the client (e.g. - browser) for the credential create call. Note that the library does not keep track of sessions or context, so the caller is expected to associate the resulting challenge with a session so that it can be appropriately matched with a response.
  2. attestationResult - parses and validates the response from the client
  3. assertionOptions - creates the challenge that will be sent to the client for credential assertion.
  4. assertionResult - parses and validates the response from the client

There is also an extension point for adding new attestation formats.

Full documentation can be found here.

For working examples see OWASP Single Sign-On and / or


  • Works with Windows Hello
  • Attestation formats: packed, tpm, android-safetynet, fido-u2f, none, apple
  • Convenient API for adding more attestation formats
  • Convenient API for adding extensions
  • Metadata service (MDS) support enables authenticator root of trust and authenticator metadata
  • Support for multiple simultaneous metadata services (e.g. FIDO MDS 1 & 2)
  • Crypto families: ECDSA, RSA
  • x509 cert parsing, support for FIDO-related extensions, and NIST Public Key Interoperability Test Suite (PKITS) chain validation (from pki.js)
  • Returns parsed and validated data, along with extra audit data for risk engines
  • Support both CommonJS (require) and ESM (import) natively

Getting started


npm install fido2-lib --save

Import Library using CommonJS

const { Fido2Lib } = require("fido2-lib");

Import Library using ESM-syntax

import { Fido2Lib } from "fido2-lib";


Import dist/main.js from a trusted source. Below is only an example, using the official repository. It is recommended to enable integrity checking.

Get url to the latest version by going to

// Example url will always redirect to the latest version
// It is recommended that you use the method mentioned above to get a fixed url
import { Fido2Lib } from "";


Instantiate Library (Complex):

// could also use one or more of the options below,
// which just makes the options calls easier later on:
const f2l = new Fido2Lib({
    timeout: 42,
    rpId: "",
    rpName: "ACME",
    rpIcon: "",
    challengeSize: 128,
    attestation: "none",
    cryptoParams: [-7, -257],
    authenticatorAttachment: "platform",
    authenticatorRequireResidentKey: false,
    authenticatorUserVerification: "required"


const registrationOptions = await f2l.attestationOptions();

// make sure to add
// save the challenge in the session information...
// send registrationOptions to client and pass them in to `navigator.credentials.create()`...
// get response back from client (clientAttestationResponse)

const attestationExpectations = {
    challenge: "33EHav-jZ1v9qwH783aU-j0ARx6r5o-YHh-wd7C6jPbd7Wh6ytbIZosIIACehwf9-s6hXhySHO-HHUjEwZS29w",
    origin: "https://localhost:8443",
    factor: "either"
const regResult = await f2l.attestationResult(clientAttestationResponse, attestationExpectations); // will throw on error

// registration complete!
// save publicKey and counter from regResult to user's info for future authentication calls


const authnOptions = await f2l.assertionOptions();

// add allowCredentials to limit the number of allowed credential for the authentication process. For further details refer to webauthn specs: (
// save the challenge in the session information...
// send authnOptions to client and pass them in to `navigator.credentials.get()`...
// get response back from client (clientAssertionResponse)

const assertionExpectations = {
    // Remove the following comment if allowCredentials has been added into authnOptions so the credential received will be validate against allowCredentials array.
    // allowCredentials: [{
    //     id: "lTqW8H/lHJ4yT0nLOvsvKgcyJCeO8LdUjG5vkXpgO2b0XfyjLMejRvW5oslZtA4B/GgkO/qhTgoBWSlDqCng4Q==",
    //     type: "public-key",
    //     transports: ["usb"]
    // }],
    challenge: "eaTyUNnyPDDdK8SNEgTEUvz1Q8dylkjjTimYd5X7QAo-F8_Z1lsJi3BilUpFZHkICNDWY8r9ivnTgW7-XZC3qQ",
    origin: "https://localhost:8443",
    factor: "either",
    publicKey: "-----BEGIN PUBLIC KEY-----\n" +
        "MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAERez9aO2wBAWO54MuGbEqSdWahSnG\n" +
        "MAg35BCNkaE3j8Q+O/ZhhKqTeIKm7El70EG6ejt4sg1ZaoQ5ELg8k3ywTg==\n" +
        "-----END PUBLIC KEY-----\n",
    prevCounter: 362
const authnResult = await f2l.assertionResult(clientAssertionResponse, assertionExpectations); // will throw on error

// authentication complete!

For a real-life example, refer to OWASP Single Sign-On.

Migration from v2 to v3

Generally v3 is assumed to be completely compatible with v2 - compatibility should have increased. As many inner workings have been changed, please verify that your application still works with v3 and report issues, if you newly encounter bugs.


Setting up the environment

It's recommended to have both Deno (>=1.20) and Node 16-18 available to be able to run all checks and tests.

Before committing

Please run npm run lint, npm run test and deno task test before committing, to make sure every test and check passes.

See package.json for available npm scripts, and deno.jsonc for available Deno tasks.

Make sure to add tests if you add new features.

Important: Do not stage/commit dist/main.js and dist/main.cjs. These are generated and committed automatically by the CI-pipeline.


When adding, removing or updating dependencies, start out with npm as usual. Then update import_map.json to the same versions shown by npm list, and run deno task update-deps to update the Deno lock-file.

Pull Request

When you're finished with the changes, create a pull request.

  • Enable the checkbox to allow maintainer edits so the branch can be updated for a merge. Once you submit your PR, a team member will review your proposal. We may ask questions or request for additional information.
  • If you run into any merge issues, checkout this git tutorial to help you resolve merge conflicts and other issues.

Work for this project was supported by Adam Power.