Jpeg-Jsteg

INFORMATICA, 2004, Vol. 15, No. 1, 127–142  2004 Institute of Mathematics and Informatics, Vilnius

127

High Capacity Data Hiding in JPEG-Compressed Images
Hsien-Wen TSENG, Chin-Chen CHANG
Department of Computer Science and Information Engineering National Chung Cheng University Chaiyi, Taiwan 621, R.O.C. e-mail: {hwtseng,ccc}@cs.ccu.edu.tw Received: March 2003 Abstract. The JPEG image is the most popular file format in relation to digital images. However, up to the present time, there seems to have been very few data hiding techniques taking the JPEG image into account. In this paper, we shall propose a novel high capacity data hiding method based on JPEG. The proposed method employs a capacity table to estimate the number of bits that can be hidden in each DCT component so that significant distortions in the stego-image can be avoided. The capacity table is derived from the JPEG default quantization table and the Human Visual System (HVS). Then, the adaptive least-significant bit (LSB) substitution technique is employed to process each quantized DCT coefficient. The proposed data hiding method enables us to control the level of embedding capacity by using a capacity factor. According to our experimental results, our new scheme can achieve an impressively high embedding capacity of around 20% of the compressed image size with little noticeable degradation of image quality. Key words: JPEG, data hiding, steganography, HVS, Jpeg–Jsteg, LSB substitution.

1. Introduction Image, audio, video, and many other kinds of data are nowadays mostly passed from person to person or from place to place in a digital form. It is often desirable to embed data into the digital contents for copyright control and authentication, or for secret data hiding. Data-embedding techniques designed to take care of such tasks are commonly classified as watermarking or data hiding techniques in accordance with their functionalities. Watermarking techniques are often further divided into two

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