Recently, the security of RSA variants with moduli N = pr q, e.g., the Takagi RSA and the prime power RSA, have been actively studied in several papers. Due to the unusual composite moduli and rather complex key generations, the analyses are more involved than the standard RSA. Furthermore, the method used in some of these works are specialized to the form of composite integers N = pr q. In this paper, we generalize the techniques used in the current best attacks on the standard RSA to the RSA variants. We show that the lattices used to attack the standard RSA can be transformed into lattices to attack the variants where the dimensions are larger by a factor of (r + 1) of the original lattices. We believe the steps we took present to be more natural than previous researches, and to illustrate this point we obtained the following results: – Simpler proof for small secret exponent attacks on the Takagi RSA proposed by Itoh et al. (CT-RSA 2008). Our proof generalizes the work of Herrman...