NIP-46 relay session

draft

Where the decrypted bridge only converts an already-decrypted payload into a decision, the relay session is the layer that actually talks to a remote signer over Nostr relays: it opens the relay, encrypts and decrypts the NIP-44 envelopes, correlates requests with responses, and verifies the returned event. It is built in @nsealr/nip46 and consumes the frozen nsealr-nip46-session-active-v0 contract from nSealr/specs.

Layers

The session is composed from small, independently tested units:

Layer	What it does	Module
Relay transport	publish / subscribe-by-filter / close, I/O only	`RelayTransport` (`InMemoryRelay` fake, `NostrToolsRelay` for production)
NIP‑44 v2	authenticated encryption of the envelope payload	`@nsealr/core` `nip44` (hand-rolled ChaCha20 + HMAC-SHA256)
Session protocol	build a signed + encrypted kind‑24133 event; decrypt + verify one	`buildNip46RequestEvent` / `decryptNip46Event`
Session manager	the `idle → session_active → session_closed` state machine, id‑correlated timed request/response	`Nip46SessionManager`
Verification	recompute the NIP‑01 id and check the BIP‑340 signature of the returned event	`@nsealr/core` `verifySignedEventResponse`
Persistence	secretless session record (metadata only)	`SessionStore` / `toActiveSessionRecord`

Flow

connect — the manager subscribes for kind‑24133 events addressed to the client (#p = client pubkey), then publishes an encrypted connect request and waits for the signer’s ack.
session_active — signEvent(template) publishes an encrypted sign_event request; the matching response is decrypted, then the returned event is verified (NIP‑01 id recompute + BIP‑340 signature + same-template check) before it is handed back. An unmatched or malformed response is rejected, not silently dropped.
session_closed — the relay subscription is closed and any in‑flight request is rejected.

Every transport event is verified on the way in (kind 24133, recomputed id, BIP‑340 signature) and checked to be addressed to this recipient before it is NIP‑44‑decrypted.

Cryptography stays hand-rolled

NIP‑44 v2 is implemented in @nsealr/core from @noble primitives (secp256k1 ECDH → HKDF schedule → ChaCha20 → HMAC‑SHA256), not delegated. Its correctness is pinned by a dual oracle: the official NIP‑44 v2 test vectors and a differential test against nostr-tools/nip44. nostr-tools is used in production only for relay transport (SimplePool); it never touches the signing or verification path.

Persistence is secretless

A persisted session is a contract-conformant nsealr-nip46-session-active-v0 record — pubkeys, relays, connect digest, approved permissions, lifecycle phase. It never stores the client transport key, the NIP‑44 conversation key, or any other secret material; the record is validated through the same parser the contract defines, which rejects any secret-bearing field.