Everyone knows ZK started with privacy but Part 4 shows the real story: it’s now the backbone for products users actually feel. @brevis_zk ❯ Privacy: shield the data, keep the math honest. Valid txs without leaking sender/amount useful, but only the opening act. ❯ Scaling: rollups batch the heavy lift off-chain and post a tiny proof on L1. The key isn’t secrecy, it’s succinctness constant-time verify, predictable fees. (EF’s “Realtime Proving” target is sub-10s; Brevis’s Pico Prism has already demoed ~6.9s avg with 96.8% <10s for 45M-gas blocks.) ❯ Bridges: prove state across chains instead of trusting committees one proof, many verifiers. ❯ Identity: selective disclosure beats doxxing “passed KYC,” “over 18,” “holder for 90d” without spraying your wallet history. ❯ Verifiable compute: where this gets fun. Compute off-chain, return a tiny ZK receipt on-chain so contracts can “remember” history and adapt in real time. Receipts users can touch today: ❯ PancakeSwap-style loyalty: personalized fees/LP rewards based on real trading history (math off-chain, proof on-chain). ❯ Linea Ignition payouts: rewards for useful liquidity, not parked TVL. ❯ Kaito leaderboards: ZK credentials for multipliers holders stay private, boosts stay legit. If you’re building, start with one perk that was gas-impossible before (e.g., 30-day volume tier). Score it in Rust on Pico, verify once in a tiny Solidity callback, and let the proof be the product