A steganographic method based upon JPEG and particle swarm optimization algorithm

In this paper, a novel steganographic method, based on JPEG and Particle Swarm Optimization algorithm (PSO), is proposed. In order to improve the quality of stego-images, an optimal substitution matrix for transforming the secret messages is first derived by means of the PSO algorithm. The standard JPEG quantization table is also modified to contain more secret messages. The transformed messages are then hidden in the DC-to-middle frequency components of the quantized DCT coefficients of the cover-image. Finally, a JPEG file with secret messages is generated through JPEG entropy coding. We compare our algorithm with Chang et al.'s JPEG-based steganographic algorithm. The experimental results show that our proposed method has larger message capacity and better image quality than Chang et al.'s. In addition, our method also has a high security level. (c) 2007 Elsevier Inc. All rights reserved.