关键词: 纯密码 不变子集 互信息

Abstract:

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.

Key words: pure cipher,invariant subset,mutual information