Sipster - Settling IOU Privately and Quickly with Smart Meters.

Cyber-physical systems revolutionize how we interact with physical systems. Smart grid is a prominent example. With new features such as fine-grained billing, user privacy is at a greater risk than before. For instance, a utility company () can infer users’ (fine-grained) usage patterns from their payment. The literature only focuses on hiding individual meter readings in bill calculation. It is unclear how to preserve amount privacy when the needs to assert that each user has settled the amount as calculated in the bill. We advocate a new paradigm of cash payment settlement enabling payment privacy. Users pay their bills in unit amount so that they can hide in the crowd. Meanwhile, can obtain payments earlier in the pay-as-you-go model, leading to a win-win situation. A highlight of our proposed system, Sipster, is that the receipts for the payments can be combined into a O(1)-size receipt certifying the smart meter’s certification. Without such aggregation, techniques such as zero-knowledge proof would fail since it typically cannot hide the size of the witness. Seemingly helpful tools, e.g., aggregate signatures or fully homomorphic signatures, also fail. The novelty of Sipster lies in fulfilling our five goals simultaneously: 1) privacy-preserving: the cannot infer a user’s payment amount; 2) prover-efficient: no zero-knowledge proof is ever needed; 3) verifier-efficient: it takes O(1) time to verify a combined receipt; 4) double-claiming-free: users cannot present the same receipt twice; and 5) minimalistic smart meter: it has the capability to report signed readings (needed even in a non-private setting).