Information security is an important task in the digital age, and one of the ways to protect data is to use cryptographic methods. This paper discusses the problem of creating new combinatorial generation algorithms that can later be used as a mathematical basis for solving specific problems in the field of cryptography. For example, as a result of applying a ranking algorithm to a text over some alphabet, it will be encoded with the appropriate rank value. If some of the information that was used in this encoding process is declared as a secret, then the reverse decoding will become a difficult task. According to this idea, we proposed a method for designing encoding and decoding functions by using combinatorial generation algorithms that is based on applying AND/OR tree structures. Several examples of implementing the steps of the proposed method are also presented.