The presentation of Magma and $2$-GOST block cipher semibyte substitutions by algebraic threshold functions

The paper deals with the implementation of Magma and $2$-GOST block cipher semibyte substitutions by algebraic threshold functions (ATF). For each Magma substitution, an ATF-presentation of some linear combinations of its coordinate functions is proposed. Some linear combinations of ATF representing $2$-GOST substitutions are found.