Nostr relays see everything - who connects, what they fetch, how often they post. Zero-knowledge cryptography can fix all three problems: Semaphore-based authentication hides which whitelisted user is connecting, private information retrieval hides which notes you're fetching, and Privacy Pass enables rate limiting without identity linkage.
Binary Fuse filters let Blossom clients privately check which files exist on a server - download a compact filter once, query locally with zero server load, and use delta lists for real-time accuracy.
Services no longer need to see data to compute on it. Cryptographic and hardware primitives make that contract a deployed reality.
TEE relays shift trust from operators to chip manufacturers. For most threats, that trade is worth making, with eyes open.
Can PIR hide Nostr queries from relays? Compound filters and subscriptions don't map to existing schemes. Here are the open problems.
