You can test browser-based WebAuthn registration and sign-in with an ESP32-based roaming authenticator using Zephyr’s FIDO2 Authenticator sample on a USB-capable ESP32-S3-B board. The sample identifies the weact_esp32s3_b/esp32s3/procpu target as tested for USB HID. This is a lab setup, not evidence that a homemade key is independently evaluated or suitable for protecting valuable accounts.
What you are setting up
WebAuthn is the browser-facing API used by a website to register a public-key credential and later verify an authentication assertion. A hardware security key provides the authenticator behavior behind that browser flow, using FIDO protocols such as CTAP over a supported transport. The W3C Web Authentication Level 2 specification describes credentials scoped to a relying party and lists USB, Bluetooth Low Energy, and NFC as transports for roaming authenticators.
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The W3C describes its purpose this way: “This specification defines an API enabling the creation and use of strong, attested, scoped, public key-based credentials by web applications, for the purpose of strongly authenticating users.” For this walkthrough, the transport is USB and the test relying party is webauthn.io.
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Choose a board and firmware route
Use an ESP32-S3-B board that matches Zephyr’s documented target, weact_esp32s3_b/esp32s3/procpu. The sample lists this target as tested for USB HID. Do not assume that a generic ESP32 board can act as a USB device: board variants differ, and the documented result does not establish compatibility for every ESP32 or ESP32-S3 board.
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Build and flash Zephyr’s FIDO2 Authenticator sample for the matching board identifier, following the current sample documentation and confirming the Zephyr version and board revision for your hardware. The available setup information does not establish a single version-specific command sequence, so do not substitute another board identifier or copy commands intended for a different Zephyr release.
Run a registration and sign-in test
- Flash and connect: After flashing the sample, connect the board to your computer through its USB port.
- Open a test relying party: In a compatible browser, open webauthn.io and use a disposable username. Keep this experiment separate from accounts you rely on.
- Register: Start the site’s registration flow. When the browser asks for a security key, press the board’s configured user-presence button. If the authenticator or browser flow asks for a PIN, enter or set one as prompted.
- Authenticate: Use the newly registered test credential to start sign-in. Press the user-presence button again when prompted.
- Record the result precisely: Note separately whether the firmware compiled, was uploaded, enumerated over USB, passed a protocol probe, and completed registration and sign-in in the browser. Compilation alone does not demonstrate that the board works as a USB authenticator or completes a WebAuthn ceremony.
Choose credential and verification settings deliberately
A community ESP32-S3 lab project reports a WebAuthn.io configuration using cross-platform attachment, user verification discouraged, attestation none, ES256, and non-discoverable credentials for non-resident testing. It says discoverable credentials are needed for its resident-credential tests. Those are project-specific reported settings, not universal requirements: browser behavior, relying-party choices, and authenticator firmware can change what works.
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Choose user verification for the use case rather than treating a PIN prompt as a failure. Yubico’s WebAuthn readiness guidance notes that second-factor flows commonly discourage user verification to avoid an unnecessary PIN prompt. For an integration test, keep these dimensions distinct:
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- Authenticator behavior: supported CTAP operations and PIN or user-verification behavior.
- Credential type: discoverable versus non-discoverable credentials.
- Evidence: compile, upload, USB enumeration, protocol probe, and an actual browser ceremony.
Know what this ESP32 test does not establish
The cited Zephyr documentation describes the ESP32-S3-B sample for USB HID. Its BLE-tested target on the same documentation page is the nRF54LM20DK, not the cited ESP32 target. The documentation also warns that BLE operations can take longer than USB HID because a BLE connection may disconnect and be re-established between operations. Do not infer a tested BLE setup for this ESP32 board from the USB sample.
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A successful browser ceremony demonstrates that a particular board, firmware, browser, and relying-party flow worked together in that test. It does not establish independent security evaluation or production suitability. A separate ESP32 lab project explicitly labels its implementation lab-only, reinforcing the need to describe results at the level actually demonstrated.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Production security is a separate engineering task
Espressif’s ESP-IDF 5.2 security guidance discusses Secure Boot to ensure only authenticated software executes, flash encryption to protect off-chip flash contents, and encrypted NVS for device-specific data. These platform-level controls do not by themselves certify an authenticator or prove that a WebAuthn implementation is secure.
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- 1PCS 30Pin ESP32 Development Board 2.4GHz WiFi Dual Cores Microcontroller Integrated with Antenna RF Low Noise Amplifiers Filters
Do not enable eFuses or disable download access casually. Depending on the target and configuration, security settings can have irreversible or recovery consequences; disabling UART download mode can prevent esptool from working. Confirm the exact device, configuration, and recovery plan before changing them.
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- 2.4GHz Dual Mode WiFi + Bluetooth Development Board
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Sources and scope
- Zephyr Project, FIDO2 Authenticator sample documentation: target, USB setup, and browser test flow.
- W3C, Web Authentication: An API for accessing Public Key Credentials, Level 2 Recommendation, dated April 8, 2021: WebAuthn registration, authentication, and transports.
- Yubico, WebAuthn Readiness Checklist: choosing user verification for an integration’s use case.
- Espressif, ESP-IDF Programming Guide v5.2, Security: platform security controls and download-mode caution.
- Google for Developers, Build your first WebAuthn app: WebAuthn application context.
dkyazzentwatwa/esp32-keyproject README: a separate Waveshare-based lab implementation and its stated limitations.
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