In this paper, the authors examine the problems and their possible solutions on the specifics of using equivalent instructions for the hidden embedding of information into the executable and library files. This paper considers an example of hidden embedding into an executable file of exe format or into a similar elf-format for the Unix/Linux systems. In order to embed information into an executable code by the synonyms substitution method, it is suggested to use instructions that execute one and the same operation and have similar length, but that are encrypted by different opcodes.