Janjua, Faiza Younas (2008) Maximum embedding capacity of JPEG images in a secure steganographic system. (MSc(R) thesis), Kingston University, .

Abstract

Steganography is a method of secretly embedding messages in digital contents in an imperceptible manner. The primary goal of a steganographer is to maximize the embedding capacity within the given digital content while ensuring that the message remains undetected, both from the human and computer systems. The main focus of this thesis is to investigate tile effect on the embedding capacity and the perceptibility of a secret message in the frequency domain of the images at different levels of JPEG quality, image content and DCT frequencies. A software framework is designed and implemented to find out the optimal JPEG quality factor, image content and he best DCT frequencies for a given JPEG image and secret message. Additionally, psychophysical experiments have been conducted to statistically determine the extent to which the secret message remains imperceptible. The results show that for most of the images, the maximum embedding capacity with minimum perceptibility is achieved when the secret message is embedded in high DCT frequencies at a given JPEG quality factor. Also, it was found that using only the chrominance signal to embed a given size of message was less perceptible than 'also using the luminance channel to embed the message.

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