50 lines
2.5 KiB
Markdown
50 lines
2.5 KiB
Markdown
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# flit protocol
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flit speaks a trimmed subset of YAW/2.1 (forward-secret signaling) — see
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`../waste-go/PROTOCOL.md` for the full spec. This file only notes where flit
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diverges.
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## What's reused as-is
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- Ed25519 device identity; `id = hex(pubkey)`.
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- Signaling: WebSocket join/challenge, sealed `to`/`from` relay (§5).
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- yaw/2.1 ephemeral-key (`ekey`) forward-secret signaling, falling back to
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static (yaw/2.0) seal if the peer doesn't send one (§6′, §6.1).
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- The `hello` identity-confirm bind over DTLS fingerprints (§6).
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- File transfer: `file-offer` / `file-accept` / `file-cancel`, chunked
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64 KiB binary DataChannel labeled `f:<xid>` (§9).
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## What's dropped
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flit has no chat, presence, multi-peer mesh, or file browsing — every
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session is exactly one peer, ends after one transfer (or a cancel/close).
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`chat`, `pm`, `reaction`, `peer_gossip`, `browse`/`get`/`files` message
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types are not implemented.
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## What's flit-specific
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- **Room naming**: flit never uses a human-chosen network name. Rooms are
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16 random bytes (128 bits), hex-encoded, generated fresh per pairing —
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`net = sha256("yaw2-net:" + random_hex)`. This is deliberately different
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from yaw2's named-network convention: a flit room must not be guessable or
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brute-forceable from the anchor's point of view, since pairing is the only
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trust mechanism (no keyring-gated network name to fall back on for an
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ephemeral session).
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- **Invite encoding**: `flit:<base64url(json)>` where the JSON is
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`{"anchor": "<wss url>", "room": "<hex>"}`. Distinct from waste-go's
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`waste:` invite format (which carries a network *name*, not a random room).
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See `pwa/src/pairing/ephemeral.ts` and `cli/cmd/flit/main.go`.
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- **Pairing trust**: two independent flows —
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- *Ephemeral* (above): trust is "whoever shows up in this freshly
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generated, never-reused room," confirmed by the `hello` signature.
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- *Persistent keyring* (`pwa/src/pairing/keyring.ts`): optionally
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remember a peer's `id` after a verified session, for repeat pairing
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without re-scanning. Not yet wired into the join flow to pin sessions
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to a specific id — currently advisory/UI-only.
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- **TURN credentials**: short-lived, minted server-side by the anchor's
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`GET /turn-credentials` (coturn `use-auth-secret` HMAC; see
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`waste-go/cmd/anchor/main.go`). The PWA fetches from there. The CLI
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computes the HMAC locally from `FLIT_TURN_SECRET` env (acceptable for a
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native binary — unlike browser JS, it isn't visible to anyone who opens
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the page source).
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