Homomorphically Encrypted Arithmetic Operations Over The Integer Ring

Fully homomorphic encryption allows cloud servers to evaluate any computable functions for clients without revealing any information. It attracts much attention from both of the scientific community and the industry since Gentry's seminal scheme. Currently, the Brakerski-Gentry-Vaikuntanathan scheme with its optimizations is one of the most potentially practical schemes and has been implemented in a homomorphic encryption C++ library HElib. HElib supplies friendly interfaces for arithmetic operations of polynomials over finite fields. Based on HElib, Chen and Guang (2015) implemented arithmetic over encrypted integers. In this paper, we revisit the HElib-based implementation of homomorphically arithmetic operations on encrypted integers. Due to several optimizations and more suitable arithmetic circuits for homomorphic encryption evaluation, our implementation is able to homomorphically evaluate 64-bit addition/subtraction and 16-bit multiplication for encrypted integers without bootstrapping. Experiments show that our implementation outperforms Chen and Guang's significantly.