A method to generate final software code resistant to reverse engineering analysis from an initial software code, said initial software code transforming an input data to an output data, said final software code being executed by a processor being able to directly handle data of a maximum bit length M, comprising the steps of: building a conversion table comprising in one side one instruction and in the other side a plurality of equivalent instructions or sets of instructions; splitting the input data into a plurality of segments of random length, said segments having a length equal or smaller than the maximum bit length M; for each instruction of a block of instructions, selecting pseudo-randomly an equivalent instruction or set of instructions from the conversion table so as to obtain an equivalent block of instructions; and appending the plurality of equivalent blocks of instructions to obtain the final software code.