Abstract: Symmetric cryptographic algorithm description language(SDI_SCA) describes the design ideas of algorithm in a natural way of thinking similar to the professional language. In the design of cryptographic algorithms, the components of algorithm which has safe and good performanc will be repeatly used, such as Substitute, Permutation. In this paper, based on the analysis of designing rules and features of a large number of public cryptographic algorithms, the function scheme was added to SDLSCA. Key technictues of the SDLSCA function were proposed in detail such as definition, call- ing and implementation. AES was described to illustrate the application of the function. I}he practice indicates that by making proper use of functions in SDI_SCA, algorithm description can be simplified, and the efficiency and utilization rate are improved.

Key words: Special description language for the symmetric cryptographic algorithm ( SDLSCA)，Functions, Grammar rules, AES