The set of mappings and functions (transformations) that are applied to a cryptographic secure pseudo-random sequence generator (CSPRSG), specify the security strength of that generator. Various types of transformations are suggested and a considerable number of generators are designed accordingly. These transformations should satisfy certain types of prescripts to produce a good CSPRSG. We found that a class of transformations within a certain generator gives guidance to the way the generator can be analyzed. In other words, the class of transformation simplifies the process of measuring the generator strength.