“…In view of these attacks, PPML protocols have been developed. Existing techniques for designing PPML protocols can be broadly classified into four categories: 1) secure multi-party computation techniques, e.g., [3,11,13,28,29,33], 2) homomorphic encryption, e.g., [24,26,35], 3) differential privacy and homomorphic encryption or secure aggregation, e.g., [9,40,42], and 4) leveraging trusted execution environments (e.g., Intel-SGX), e.g., [18,30]. In the private training using secure multi-party computation, the training data is shared using a secret-sharing protocol among a small set of servers (e.g., 2, 3 or 4-server) (e.g., [11,28,29]), and then the training is conducted and the model is secret-shared among participating servers.…”