1. A system for data processing, the system being arranged to use operands to carry out a cryptographic operation on an input message (M), the system comprising: a memory for storing instructions, the system being configured to perform, by the instructions: blinding the input message (M) using a first random variable (V) to generate a blinded input message; and blinding all intermediate results (R) of the cryptographic operation using the first random variable (V) to generate corresponding blinded intermediate results; wherein none of the operands is inverted during the cryptographic operation; wherein the blinded input message is calculated as M−V mod(N) and each blinded intermediate result is calculated as R−V mod(N), and the first random variable (V) is calculated as (B m−1 +B −2 +. .. +B+1)v, wherein N is a modulus comprising m words, each of the m words comprises n bits, v is a second random variable that is one word comprising n bits, and B is equal to 2 n .