METHOD TO SECURELY EXECUTE A MODULAR EXPONENTIATION

The present invention relates to a method to execute a modular exponentiation R=Xe mod N, said method implementing several variable registers and an indicator register m and performing looped calculations. In the invention each loop includes at least two operations from values stored in variable registers, said operations depending on the value stored in m and on the value of the bit(s) of the exponent currently processed, m indicating if the calculation is completed for the current exponent bit at the end of the operations in the current loop.