A Method of Security Gradation against RSA IEA

A key security level gradation method is proposed which is helpful to counter IEA (Iterative Encryption Attack) and provides RSA with favorable immunity against it. Firstly, we analyze the course of IEA in detail, and then present the concept of security grade of key-pair and the hierarchy of grades, and propose an algorithm that grades security grade of key-pairs. Secondly, we define the concept of attack cost, and then launch a series of experiments for the purpose of exploring the relationship between attack cost and key security grade. At last, it is demonstrated that if to choose keys properly by this method RSA is improved to be effective to counter IEA in aspect of computation power.