The Shannon cipher system with a guessing wiretapper eavesdroping through a noisy channel

In this paper, the Shannon cipher system with discrete memoryless source is considered. The wiretapper gains the noisy version of the cryptogram through the memoryless noisy channel and tries to guess the plaintext. The security level of encryption system is measured by the expected number of wiretapper´s guesses necessary to obtain a plaintext from a ciphertext. The solved problem was suggested by Merhav and Arikan. The upper and lower bounds are obtained for the guessing rate.