  This paper presents a new privacy-preserving smart metering system. Our
scheme is private under the differential privacy model and therefore provides
strong and provable guarantees. With our scheme, an (electricity) supplier can
periodically collect data from smart meters and derive aggregated statistics
while learning only limited information about the activities of individual
households. For example, a supplier cannot tell from a user's trace when he
watched TV or turned on heating. Our scheme is simple, efficient and practical.
Processing cost is very limited: smart meters only have to add noise to their
data and encrypt the results with an efficient stream cipher.
