Private Decision Tree Evaluation with Constant Rounds via (Only) SS-3PC over Ring.

Secure computation is the technology that computes an arbitrary function represented as a circuit without revealing input values. Typical technologies related to secure computation are secure multiparty computation (MPC) that uses secret sharing (SS) schemes, for example, SS-MPC, garbled circuit (GC), and homomorphic encryption (HE). These cryptographic technologies have a trade-off relationship with respect to the computation cost, communication cost, and type of computable circuit. Hence, the optimal choice depends on the computing resources, communication environment, and function related to applications. The private decision tree evaluation (PDTE) is one of important applications of secure computation. There exist several PDTE protocols with constant communication rounds that use GC, HE, and SS-MPC over the field. However, to the best of our knowledge, PDTE protocols with constant communication rounds that use SS-MPC over the ring (requiring only lower computation costs and communication complexity) is non-trivial and still missing. In this paper, we propose a PDTE protocol that uses a secure three-party computation (3PC) protocol over the ring with one corruption.