Compression and Segmentation of JPEG Images Using DWT

Hiding capacity is very important for efficient covert communications. For JPEG compressed images, it is necessary to enlarge the hiding capacity because the available redundancy is very limited. Steganography enables to have a secret communication in modern information technology using Dual Transform Technique for Robust Steganography (DTTRS) [1]. The implementation of the Dual transform technique is carried out in the following sequences. The JPEG compressed grayscale cover image is segmented into 4*4 blocks each and Discrete Wavelet Transform (DWT) is applied on each block. The blocks of vertical band of 2*2 each obtained from the resulting DWT coefficients are considered and Integer Wavelet Transform (IWT) is applied to get blocks of 1*1 each. Next, to each 1*1 Block of the cover image, the secret data is embedded using LSB replacement technique. On applying IIWT and IDWT, stego image is derived. Error Detection and Correction Code (EDCC) technique is implemented to ensure more reliable communication. For EDCC, Turbo Codes have been implemented in the field of forward error correction and high performance error correction so as to achieve maximal information over a limited bandwidth communication link. The encoded message is now hidden into the DWT and IWT transformed cover image by LSB substitution method. At the receiver side, the stego image is subjected to IIWT and IDWT. Then the encoded secret data is retrieved after error detection and correction by the decoding process.