About the possibility of recovering message based side on information about the original characters

In order to ensure secure information exchange in communication channels, a preliminary study of the correctness of the operation of the relevant information protection systems is necessary. Despite the fact that the mathematical algorithms used in such systems are correct and theoretically provide the correct statistical properties of the output stream compared to the input, at the stage of implementation (programming) of these protection algorithms or at the stages of assembling the final equipment (using hardware, making adjustments) and its operation in real conditions, it is possible to introduce distortions that violate the operation of certain elements of information security tools (for example, a random number sensor). As a result, by the nature of the transmitted signal, it becomes possible to determine that the output stream for a number of characteristics is steadily different from the ideal encrypted stream, which in theory should have come from the equipment and appeared at the output of the communication channel. In this situation, it is necessary to understand how the introduction of certain distortions affects the degree of security of the system being created. For this purpose, the parameters of various message sources are described, which simulate receiving an output stream with distortions. At the same time, the degree of security of the corresponding communication channel is proposed to be determined by estimating the proportion of the input stream that can be restored from the output using side information resulting from the introduction of appropriate distortions in the operation of the system.