Information Theoretic Analysis of RSA

In the past, people usually use the theory of computational complexity to analyze RSA security, which depends on the factor of large integer. In this paper, by using some results of Shannon’s theory of secrecy systems, we divide the message space and cryptogram space into some invariant subsets, and then compute the mutual information between messages and cryptograms. Therefore we obtain that the security parameter of RSA must be safe primes.