Samoylik Y. Lexicographical methods for speech information security

The dissertation is devoted to the creation of stable symmetric cryptosystems. A method for constructing a semantic dictionary suitable for use as part of a robust cryptosystem for protecting textual information has been developed. The structure of the thesaurus in the coordinate section is presented, which characterizes the level of abstraction of mappings of semantic images. This structure uniquely determines the location of semantic units in the thesaurus, which allows to automate the process of its creation. Formal definitions of indicators of semantic relations between semantic units, such as semantic identity, semantic difference, doubtful semantic identity (or plausibility), doubtful semantic difference (or false similarity) are introduced. A methodological approach to protecting the meaning of text messages based on the use of the relationship of semantic plausibility is proposed. In order for a cryptanalyst under no circumstances to form any idea of the truth of the meaning of intercepted text messages, it is necessary and sufficient to replace the meaning of semantic images contained in the original text messages with their plausible representations, which are taken from the corresponding thesauri of the chosen language. areas of activity.