Abstract
The development of online communications and the Internet have made encrypted data exchange fast growing. This has been possible with the development of asymmetric cryptographic protocols, which make use of arithmetic computations such as modular exponentiation of large integer or elliptic curve scalar multiplication. These computations are performed by various platforms, including smart-cards as well as large and powerful servers. The platforms are subject to attacks taking advantage of information leaked through side channels, such as instantaneous power consumption or electromagnetic radiations.In this thesis, we improve the performance of cryptographic computations resistant to Simple Power Analysis. On modular exponentiation, we propose to use multiple multiplications sharing a common operand to achieve this goal. On elliptic curve scalar multiplication, we suggest three different improvements : over binary fields, we make use of improved combined operation AB,AC and AB+CD applied to Double-and-add, Halve-and-add and Double/halve-and-add approaches, and to the Montgomery ladder ; over binary field, we propose a parallel Montgomery ladder ; we make an implementation of a parallel approach based on the Right-to-left Double-and-add algorithm over binary and prime fields, and extend this implementation to the Halve-and-add and Double/halve-and-add over binary fields.