A Steganalysis Scheme for AAC Audio Based on MDCT Difference Between Intra and Inter Frame

AAC (Advanced Audio Coding), as an efficient audio codec, has been used widely in mobile internet applications. Steganographies based on AAC are emerging and bringing new challenges to information content security. In this paper, an AAC steganalysis scheme to detect the steganographies which embedded secret information by modifying MDCT coefficient is proposed. The modification of MDCT coefficient will cause the statistical characteristic of the difference between inter-frame and intra-frame changed simultaneously. Based on this ideal, we proposed a scheme to extract combination features to classify cover and stego audio. There are 16 groups of sub-features to represent the correlation characteristics between the multi-order differential coefficients of Intra and Inter frame (MDI2), each sub-feature's performance are analyzed in this paper, and an ensemble classifier is used to realize the steganalyzer. Experiment results show that the detection accuracy of the proposed scheme are above 85.34% when the relative embed rate is over 50%, this performance is obviously better than the literatures methods. Due to the similarity of the coding principle of AAC and MP3, the proposed features can be applied into MP3 steganalysis.