Touch ID / Face ID / Windows Hello / Android fingerprint / YubiKey
(PRF-capable) can now unlock the local seed without typing the
passphrase. Fully client-side — the server has zero visibility into
the credential or the derived key.
How it works (WebAuthn PRF extension):
1. Setup (Dashboard → "Quick unlock" → "Set up biometric unlock"):
• Register a platform credential with prf:{} in extensions.
• If the authenticator returns prf.enabled, immediately
getAssertion() with a random 32-byte salt to retrieve a
deterministic 32-byte secret (the "PRF output").
• AES-GCM(seed) under that secret → store the blob, salt, nonce,
and credentialId in a separate IDB entry from the passphrase
blob.
2. Unlock (Unlock page → big "Unlock with Touch ID" button):
• getAssertion() with the stored credentialId + salt → same
32-byte secret → AES-GCM decrypt → seed.
• unlockWithSeed() (new helper in identity-store) merges the
seed with handle/server/primary metadata to rebuild the
UnlockedIdentity session shape.
Trust properties (intentional):
• Passphrase blob stays in place as the authoritative backup.
Biometric is purely additive — wipe your browser profile or lose
the device, passphrase still works on any device where you
re-import the seed.
• PRF output never leaves the browser. The authenticator is the
only thing that can produce it, and only with the matching salt
+ credentialId we stored.
• Disable → just deletes the IDB entry; the registered credential
on the device still exists but is unused. (User can also clear
it from their OS / passkey manager.)
Browser support gating:
• Dashboard panel renders "no platform authenticator detected" if
isUserVerifyingPlatformAuthenticatorAvailable() returns false.
• Setup fails with a clear error if PRF isn't supported by the
authenticator (older YubiKeys, some password managers).
• Unlock page falls back to passphrase form automatically if
biometric fails (cancelled, sensor error, etc.).
Live at https://kez.lat (asset index-Df_F5lEP.js).
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
First real UI for kez-chat. Served by the chat-server as static
files; uses the same HTTP API a native client would (dogfoods the
contract).
Stack: Svelte 5 + TypeScript + Vite + Tailwind 4 + @noble/curves +
@scure/base + canonicalize + idb-keyval + svelte-spa-router.
Bundle: 113 KB JS / 14 KB CSS (gzip: 42 KB / 4 KB).
Pages (all behind hash routing):
/ Landing — sign up or restore from seed
/create Account creation flow:
1. Pick handle, set passphrase
2. Show seed for paper backup, require ack
3. Confirm
4. POST /v1/register, save passphrase-encrypted seed
to IndexedDB
/restore Stub for restore-from-seed (v0.2: needs
GET /v1/by-primary endpoint on the server)
/unlock Enter passphrase to derive the AES-GCM key,
decrypt the seed, populate session state
/dashboard Show handle, primary, registered_at, sigchain URL
/claims List locally-cached claims (with publication status)
/claims/add Add-a-claim wizard:
1. Pick channel (github/dns/web/nostr/bluesky/ap)
2. Enter identifier
3. SignedClaimEnvelope built + signed in-browser
using Ed25519 + JCS, matching the spec exactly
4. Show channel-appropriate publish instructions +
copyable markdown or JSON artifact
5. User marks it published (purely a local note —
actual verification is the verifier's job)
Crypto / KEZ helpers (src/lib/kez.ts):
- generateIdentity / identityFromSeed (32-byte Ed25519)
- canonicalBytes (RFC 8785 JCS via the `canonicalize` package — same
one our Node port uses; produces byte-identical output to Rust)
- signClaim, signRegistration (build envelopes; sign with
ed25519-sha512-jcs; same alg / key / sig shape as kez-core)
- toPrettyJson, toMarkdown (the same wire encodings the CLI emits)
Key storage (src/lib/identity-store.ts):
- IndexedDB via idb-keyval
- Seed encrypted under user passphrase: PBKDF2-SHA256
(600,000 iterations, OWASP 2024 guidance) → AES-GCM-256
- Documented limitation: browsers don't have an OS-keychain
equivalent. Native clients (future CLI/Tauri) will use the OS
keychain for better protection.
Bundle includes:
- Workaround for TS 5.6+ Uint8Array<ArrayBufferLike> vs ArrayBuffer
strictness (small asBuffer() helper that copies into a plain
ArrayBuffer for WebCrypto + Response calls).
Dockerfile updated: now multi-stage with a Node `webbuild` stage
that runs `npm run build` before the Rust binary stage. SPA dist
is copied into the runtime image at /app/web; chat-server's
KEZ_CHAT_WEB_DIR points at it so the SPA is served at /.
What works against the LIVE deployment right now (https://kez.lat):
- Open https://kez.lat → SPA loads (113 KB JS, 14 KB CSS)
- Create account → key gen happens in browser, seed shown for
backup, encrypted under passphrase, POSTed to /v1/register
- Dashboard → shows registered handle + primary + sigchain URL
- Claims wizard → sign for any of the 6 channels, get publish
instructions + the right wire format to copy
- Lock / unlock — passphrase-derived AES-GCM, no roundtrips
What's still TODO (v0.2):
- Restore-from-seed: needs GET /v1/by-primary on the server so the
SPA can discover the handle from a seed
- Actual NATS chat: needs server's auth callout (currently 501) +
nats.ws client (browser side; package is in deps but not used yet)
- Sigchain integration: append `add` event when user publishes a
claim, upload to sig-server (needs sig.kez.lat tunnel)
- Verification: in-browser channel fetches (some channels are
CORS-friendly, others need a server-side proxy)
- Compact (kez:z1:) form: the spec uses zstd, browsers don't have
native zstd CompressionStream support yet. Workaround in code
uses deflate-raw with a `kez:zd1:` prefix to make it obvious the
output isn't spec-compliant; replace with @bokuweb/zstd-wasm or
similar when we need true compact form in the SPA.
Jason Tudisco
Tudisco