A METHOD FOR PROTECTING A SUBSTITUTION OPERATION USING A SUBSTITUTION TABLE AGAINST A SIDE-CHANNEL ANALYSIS

摘要

The invention relates to a method for executing by a circuit a substitution operation whereby an output data is selected in a substitution table using an input data as an index, wherein the substitution operation is performed using a new masked substitution table (SB1), the input data being combined by XOR operations with a new value of a first mask parameter (u1), and the output data being combined by XOR operations with a new value of a second mask parameter (v1), the new masked substitution table being generated by computing the new value of the first mask parameter by applying XOR operations to a previous value of the first mask parameter (u0) and to a first input mask (U); computing the new value of the second mask parameter by applying XOR operations to a previous value of the second mask parameter (v0) and to a second input mask (V), and generating the new masked substitution table using a previous masked substitution table (SB0) and the first and second input masks.