Extends the Block 2 spike to attack the highest-risk unbuilt piece (private
messaging) and to prove the Q2 architecture recommendation with running code:
- NostrConnection: one shared socket+key+sign+REQ/EOSE lifecycle. Refactored
NostrOfferTransport onto it; added NostrMessageTransport — two thin contracts
on ONE connection (the 'one connection, three interfaces' shape).
- NIP-44 v2 encryption (secp256k1 ECDH -> ChaCha20 + HMAC, length-hiding pad).
- NIP-17/NIP-59 gift-wrap: rumor(14) -> seal(13) -> wrap(1059, ephemeral key).
Alice->Bob DM round-trips through the relay: encrypted, sender authenticated,
and metadata-private (relay/eavesdropper sees only ciphertext, an ephemeral
author and the recipient p-tag — Alice stays hidden).
Findings updated: NIP-17 risk drops Medium-High -> Medium (hardening, not
feasibility); next de-risking target is the web of trust. NIP-44 not yet
vector-verified (noted). 20 tests green, analyzer clean, Block 1 untouched.
Throwaway research spike (spike/ branch, outside pub workspace, no prod deps
touched). Validates the open Block 2 decisions before committing a funded round:
1. Deterministic one-way secp256k1 (Nostr) key derived from the Ğ1 root seed
via HKDF — user still backs up ONE thing. Reproducible + signs (BIP340).
2. OfferTransport abstraction over Nostr NIP-99 (kind 30402); Offer stays
inventory/location-agnostic, geohash coarsened on the wire (tested).
3. publish->discover-by-geohash proven end-to-end against an in-process
hermetic mini-relay (~34ms round-trip).
Findings + risks + recommendation in docs/design/spike-block2-findings.md.
Block 1 suite untouched. 14 tests green, analyzer clean.
