1 Introduction
Homomorphic Encryption schemes are considered as promising in modern cryptography, because they directly allow to carry out operations on data in the cipher domain. Fig. 1 illustrates a basic client/server transaction in an homomorphic scenario. The most flexible ones, called Fully Homomorphic Encryption (FHE) schemes, are able to process unlimited additions and multiplications secretly, and so make possible to address a wide range of algorithms. To reduce computation times, many applications only consider Somewhat Homomorphic Encryption (SHE) schemes, which bound the number of operations to reduce the complexity.