Towards practical homomorphic email filtering - a hardware-accelerated secure naïve bayesian filter.

A secure version of the naïve Bayesian filter (NBF) is proposed utilizing partially homomorphic encryption (PHE) scheme. SNBF can be implemented with only the additive homomorphism from the Paillier system, and we derive new techniques to reduce the computational cost of PHE-based SNBF. In the experiment, we implemented SNBF both in software and hardware. Compared to the best existing PHE scheme, we achieved 1,200x (resp., 398,840x) runtime reduction in the CPU (resp., ASIC) implementations, with additional 1,919x power reduction on the designated hardware multiplier. Our hardware implementation is able to classify an average-length email in 0.5 s, making it one of the most practical NBF schemes to date.