Mathematical methds of formation multialphabetic codes of replacement

In the suggested cipher each symbol (the letter, a punctuation mark, number) is replaced with two real numbers. These two numbers are top and bottom limits of the determined integral. Value of integral is used that under the table of replacements to define, to what symbol of a open text there corresponds the calculated value of integral. It is supposed, that the kind of sub-integral function and a configuration of the table of replacements are known only to authorized representatives on the transmitting and reception sides. In each session of communication the table of replacements and sub-integral function are defined by a confidential key.