Coding Theorems for the Shannon Cipher System With a Guessing Wiretapper and Correlated Source Outputs

The security level of the Shannon cipher system is traditionally measured by equivocation, where is a secret plaintext with length and is its cryptogram. But, Merhav and Arikan have considered another security criterion, which is measured by the number of guesses needed for a wiretapper to uncover from . Merhav has also considered the third security criterion, which measured by the probability of correct guess of a wiretapper. On the other hand, in the case of the traditional security criterion, Yamamoto has treated a coding problem for correlated source outputs and such that only is secret against wiretappers and only must be transmitted to a legitimate receiver. In this correspondence, coding theorems are proved for the case that Yamamoto's coding problem is applied to Merhav-Arikan's security criterion or Merhav's security criterion.