Trinocchio: privacy-preserving outsourcing by distributed verifiable computation

Verifiable computation allows a client to outsource computations to a worker with a cryptographic proof of correctness of the result that can be verified faster than performing the computation. Recently, the highly efficient Pinocchio system was introduced as a major leap towards practical verifiable computation. Unfortunately, Pinocchio and other efficient verifiable computation systems require the client to disclose the inputs to the worker, which is undesirable for sensitive inputs. To solve this problem, we propose Trinocchio: a system that distributes Pinocchio to three (or more) workers, that each individually do not learn which inputs they are computing on. We fully exploit the almost linear structure of Pinochhio proofs, letting each worker essentially perform the work for a single Pinocchio proof; verification by the client remains the same. Moreover, we extend Trinocchio to enable joint computation with multiple mutually distrusting inputters and outputters and still very fast verification. We show the feasibility of our approach by analysing the performance of an implementation in a case study.