Authnkey

Authnkey is an Android application that acts as a passkey credential provider, letting a hardware security key stand in for the passkeys that apps and websites request. Instead of storing credentials in the phone itself, the app routes registration and sign-in requests to an external key, so the private key material stays on the separate device.

Because it registers itself with Android's credential provider system, Authnkey appears alongside other passkey sources when an app or browser triggers a passkey prompt. The user selects it, presents the hardware key, and the resulting assertion is passed back to the requesting application. This makes it relevant to people who already carry a security key and want the same key to cover passkey logins on mobile as well as on a desktop.

Distribution is limited to Android; there is no desktop counterpart. The source is published by Michel Le Bihan under the MIT license.