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SDK Documentation Spark
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Passkey login

Passkey login lets users access their wallet using biometrics (fingerprint or face recognition) or a device PIN, eliminating the need to write down and safeguard a seed phrase.

No keys or seed phrases are stored. The SDK uses the WebAuthn PRF extension to deterministically derive a seed phrase from the user's passkey on-demand, and regenerates it on each sign-in.

One passkey can be associated with multiple wallets, each under its own label, discoverable across the user's devices through Nostr relays.

  • Setup - host the Web / Android / iOS configuration files that tie passkeys to your app.
  • Onboarding - initialize the client and wire up the sign-in, register, and unified onboarding flows.
  • Credential metadata - pin a returning user, prevent duplicate registrations, and show the authenticator and sync status.
  • Managing labels - derive multiple wallets from one passkey and discover them through Nostr.
  • PRF providers - use the built-in platform provider, or implement a custom one (hardware key, FIDO2, file-backed).

Further reading

  • UX guidelines - recommended onboarding UX, prompt counts, and error-recovery patterns.

For the full technical specification, see the Passkey Login spec.