How Napstr Uses Nostr

Nostr is Napstr’s public discovery layer and encrypted negotiation channel. Audio bytes are never uploaded to Nostr relays.

What Type Is a Track?

A shared track is a custom parameterized-replaceable event of kind 30421. The event is signed by the seeder’s Napstr identity.

Kind: 30421

Identity: the d and x tags contain the full-file SHA-256

Tags: t=napstr, filename, byte size, MIME type and alt text

JSON: the indexed filename, audio format, MIME type and byte size

Not included: audio bytes, local file path, Tor address or transfer capability

Republishing the same 30421 + d pair replaces that seeder’s previous record. Removing a share publishes a replacement marked deleted.

Napstr Event Map

Kind	Purpose	Visibility
0	Napstr profile name, description and picture	Public
10050	NIP-17 inbox relay list	Public
30421	Signed track catalogue record	Public
30422	Expiring batches of file IDs currently being seeded	Public
NIP-17	Download request, refusal, onion address and capability	Encrypted gift wrap
1984	NIP-56 catalogue reports	Public and signed

Seeder heartbeats expire after ten minutes and are refreshed every four minutes. Search groups identical SHA-256 IDs and ranks tracks by active seeders.

From Search to Download

Napstr fetches public 30421 catalogue events and live 30422 heartbeats.
The downloader sends selected seeders an encrypted NIP-17 request containing only a request ID and file ID.
A seeder replies with its private app-session Tor onion and a random, short-lived per-file capability inside NIP-17.
The audio transfer then leaves Nostr entirely and continues over Tor.

What Is Public?

Public: profile metadata, filenames, descriptive metadata, SHA-256 file IDs, reports, and which profiles advertise each file ID.
Encrypted: download requests, onion addresses and capabilities.
Local: the Nostr secret key, filesystem paths and audio contents.

A Nostr relay can normally see the IP address connecting to that relay, along with public catalogue activity and encrypted-message timing. NIP-17 hides the message plaintext; it does not make the relay connection itself anonymous. Napstr stores its dedicated Nostr key in the operating-system keyring.