Whitewash: outsourcing garbled circuit generation for mobile devices

Garbled circuits offer a powerful primitive for computation on a user's personal data while keeping that data private. Despite recent improvements, constructing and evaluating circuits of any useful size remains expensive on the limited hardware resources of a smartphone, the primary computational device available to most users around the world. In this work, we develop a new technique for securely outsourcing the generation of garbled circuits to a Cloud provider. By outsourcing the circuit generation, we are able to eliminate the most costly operations from the mobile device, including oblivious transfers. Our proofs of security show that this technique provides the best security guarantees of any existing garbled circuit outsourcing protocol. We also experimentally demonstrate that our new protocol, on average, decreases execution time by 75% and reduces network costs by 60% compared to previous outsourcing protocols. In so doing, we demonstrate that the use of garbled circuits on mobile devices can be made nearly as practical as it is becoming for server-class machines.