Hiding secret data by using modulo function in quad difference expansion

In this digital era, protecting sensitive data, such as military and financial data, has been an important factor for preventing attackers from illegally disclosing them. This protection can be done by hiding the secret into digital data (e.g., image, audio) which act as a cover. So, the secret messages cannot be seen easily. It is intended that the attacker is not able to detect the presence of the secret messages, while the authorized receiver is able to get it easily by using the extraction algorithm. A popular method for steganography is Difference Expansion (DE) whose common problem, similar to other methods, is the capacity of the secret which can be hidden and the quality of the stego data. In this paper, we propose to change the secret message into a series of base three numbers and compare it with modulo three of the difference between each quad pixel. The new pixel value is relatively close to its original one because the changes are limited between −2 to +2. The experimental result shows that the image is able to accommodate more secret messages while still maintaining the quality.