ON PERFECT IMITATION RESISTANT CIPHERS OF SUBSTITUTION WITH UNBOUNDED KEY

Abstract

Constructions of perfect imitation resistant ciphers are investigated in the work. It is well known that Vernam cipher with equiprobable gamma is a perfect cipher but it is not imitation resistant. It is because in Vernam cipher equipotent alphabets for plaintexts and ciphertexts are used. On the basis of A.Yu. Zubov's mathematical model of substitution cipher with unbounded key a model of perfect and imitation resistant cipher is constructed. At that reference cypher of the given model is perfect and reaches lower boundaries for success probability of imitation and substitution of communication.