Iroh Global Content Discovery

The piece explains a practical design for global, permissionless content discovery for iroh blobs by leveraging the proven BitTorrent Mainline DHT and replacing BitTorrent’s transfer protocol with a BLAKE3-verified streaming protocol called iroh-blobs. BLAKE3 streaming needs only a single root hash and validates arbitrary ranges without intermediate piece hashes, which makes multiprovider downloads easier to validate and superior to BitTorrent’s piece-hash model. Because Mainline is a massive, stable UDP-based DHT with extreme minimalism (single-packet queries/responses, short-lived publish tokens, provider records limited to host:port), it provides fast, global lookups; the design accepts Mainline’s constraints and uses its scalability and low per-node state as foundational infrastructure.

To bridge Mainline’s host:port provider records and iroh’s identity-based endpoints (Ed25519 EndpointId), the design adds a tiny UDP address index service that stores signed 1 KiB metadata blobs mapping a verified UDP host:port to an EndpointId. Writes require token-based reachability proof and records are last-writer-wins with expiration; reads use padded single-packet queries. Announcing content means publishing the signed endpoint record to the addr-index and calling announce_peer for the SHA-1 of the BLAKE3 root; discovery uses get_peers to obtain host:ports, translates them via addr-index lookups, then verifies content against the BLAKE3 hash. The address-index is intentionally simple, in-memory, independent of iroh, and proposed as a candidate Mainline extension.