Improvement Capacity and Transparency, In Steganography Based On Mod4

The secure and hidden communication, is one of the essential requirements in cyberspace. Steganography is the best approach, in which the communication security in common network like Internet, is provided. Steganography based on Mod 4 is one of the prevalent methods in DCT transformation domain which embeds the message in the image in different way from the past methods. In this method, correlation between coefficients is kept well and is robust against blind steganalysis .
The ultimate of this paper is to improve steganography based on Mod 4 , that is, increasing capacity and transparency, as two principal criteria in steganography. In the proposed method, by changing the size of GQC blocks and by determining the suitable conditions for choosing the valid blocks, transparency is increased more than 5 percent and capacity is increased more than 86 percent .
For evaluation the stego images transparency in the proposed method, and comparing with basic Mod4 method, two criteria, PSNR and SSIM are used .