Abstract
According to the confidential information secure transmission problem, put forward an application layer protocol steganography system based on cryptographic SM algorithm.This system based on the encryption and authentication of SM cryptographic algorithm, according to the characteristics of the application layer protocol steganography in frame type and plug-in design, elaborate the main part of system:the transmitting terminal and receiving terminal, build the system overall framework and carry on the system test.Experimental results show that this system can effectively to encrypted transmission of confidential information, realized the function of extensible and multiple protocols concurrently, which has a certain theoretical significance and practical value.