Wednesday, July 27, 2011
High Embedding Capacity Steganography Scheme for both Gray Scale and Color Images [MATLAB Code]
Steganography is a technique to hide secret messages in a host media called cover media. The advantage of steganography over cryptography is that messages do not attract attention to attackers and even receivers. Steganography and cryptography are often used together to ensure security of the secret messages.
Hiding capacity is very important for efficient covert communications. In addition, the bit stream truncation makes it difficult to hide information. In this project, a high-capacity steganography scheme is proposed based on DCT and which uses bit-plane encoding procedure, where DCT is used to transform original image (cover image) blocks from spatial domain to frequency domain. An image of size M × N is divided into non overlapping 8 × 8 blocks and a two dimensional Discrete Cosine Transform(2-d DCT) is performed on each of the P = MN / 64 blocks. Then Huffman encoding is also performed on the secret messages/images before embedding and each bit of Huffman code of secret message/image is embedded in the frequency domain by altering the least significant bit of each of the DCT coefficients of cover image blocks.
The experimental results show that the algorithm has a high capacity and a good invisibility. Moreover PSNR of cover image with stego-image shows better results in comparison with other existing steganography approaches. Furthermore, satisfactory security is maintained since the secret message/image cannot be extracted without knowing decoding rules and Huffman table.