Side-channel attacks are a serious threat against secret data involved in cryptographic calculations , as for instance pairing-based cryptography which is a promising tool for the IoT. We focus our work on Correlation Power Analysis (CPA) attack against a pairing implementation. We improve a vertical side-channel analysis attack and propose the first horizontal attack against a pairing implementation. First, we present a characterization of the multiplication that allows us to reduce by a factor of ten the number of side-channel traces required in order to perform a CPA attack against an implementation of Ate pairing. Secondly , we successfully attack the same implementation with only one trace by using the first horizontal attack path against pairing-based cryptography.