Non-endomorphic perfect ciphers with two elements in plaintext alphabet

This paper deals with the non-endomorphic perfect ciphers in the case when the plaintext alphabet consists of two elements. According to Shannon, these ciphers are absolutely immune against the attack on ciphertext. In terms of linear algebra on the basis of Birkhoff's theorem (about the classiffcation of doubly stochastic matrices), the matrices of cipher keys probabilities are described. The set of possible values of apriori probabilities for elements of ciphertext alphabet is constructed.