关键词: 密写, 小波变换, 小波对比度

Abstract: For steganography，using the wavelet contrast to decide the embedding depth in Least-Significant-Bit（LSB） can improve the hiding capacity and maintain a good visual quality of the stego-image.A new method is presented based on wavelet contrast.Firstly，the image is divided into blocks and set the least 4 bits of each pixel as 0，then decomposes with one-level wavelet transform to get the wavelet contrast and obtain the number of bit-planes for embedding.Finally，the secret information is embedded in LSB according to the different embedding length for each image block.The experimental results demonstrate the proposed method can hide large information，while maintain a good visual quality of the stego-image.Meanwhile，the embedded data can be extracted from the stego-image without any additional information.

Key words: steganographic method, wavelet transform, wavelet contrast