The properties and constructions of unconditionally strong ciphers called by K. Shannon perfect in relation to various crypto attacks are presented. Perfect ciphers with the minimum possible number of keys are distinguished, as well as resistant to attempts at deception by an attacker. For researchers, graduate students specializing in mathematical problems of cryptography, teachers and students studying the discipline & # 96; Cryptographic methods of information protection & # 96; in specialties & # 96; Computer security & # 96;, & # 96; Comprehensive security of automated systems & # 96;, & # 96; Information security of telecommunication systems & # 96;.