Diqun Yan

Steganography for MP3 audio by exploiting the rule of window switching

MP3 audio is a promising carrier format for covert communication because of its popularization. In this paper, we propose an MP3 steganographic method by exploiting the rule of window switching during encoding. The method carries out embedding by establishing a mapping relationship between the secret bit and the encoding parameter, namely window type. The proposed algorithm is fully compliant with MP3 compression standard and the distortion caused by steganography can be controlled automatically by the distortion adjustment mechanism of the encoder. Experimental results demonstrate that the proposed method introduces insignificant perceptual distortion and is statistically undetectable for the attack of block size analysis.

Steganalysis for MP3Stego using differential statistics of quantization step

MP3Stego is a typical steganographic tool for MP3 audio, which embeds secret message into MP3 audio according to the parity of the block length. In this paper, a detection method for MP3Stego based on the differential statistics of quantization step is present. By analyzing the algorithm of MP3Stego, we find that the quantization step which is an important parameter of MP3 encoding is affected during embedding. The standard deviation of the second-order differential sequence from quantization step is adopted as the classification feature. Experimental results indicate that the proposed algorithm is effective in detecting MP3Stego and can achieve better detection performance than the existing algorithms.

Steganalysis of MP3Stego with low embedding-rate using Markov feature

MP3Stego is a typical steganographic tool for MP3 audios, whose embedding behavior disturbs the intrinsic correlation of the quantized MDCT coefficients (refer to as QMDCTs). In this paper, the Markov feature captured this correlation were designed based on the QMDCTs. The feature is sensitive to the subtle alteration caused by MP3stego embedding even at a low embedding-rate. In addition, some work on QMDCT pre-processing, threshold selection and feature optimization were applied to feature construction, which contribute to improving the detection accuracy and reducing the computational complexity of the proposed scheme. Experimental results show that our approach can effectively detect MP3Stego of low embedding-rate and outperforms the prior arts.

An efficient algorithm for double compressed AAC audio detection

As a new generation of compression encoding standard, MPEG-2/4 Advanced Audio Coding (AAC) would be a widely-used audio format in the near future. However, these AAC audios often be forged by audio forgers for their own benefits in some significant events, which will cause double AAC compression. In this paper, the probability values and Markov features based on the Huffman codebook indexes of AAC audio were constructed and an efficient algorithm is proposed to detect double compression. Experimental results demonstrate that our method has high detection accuracy and low computational complexity. To the best of our knowledge, it is the first time to apply double compression detection to AAC audio forensics.

The filterbank in MP3 and AAC encoders: A comparative analysis

MP3 and AAC both use the filterbank to convert audio signal from time domain to frequency domain, which plays an important role in the whole encoder processing. Analysis the application of the filterbank in MP3 and AAC will help to understand the difference of them in coding efficiency and audio quality better. Therefore, from three points, which are the components of filterbank, the selection of window shape and the type of the translation block, this paper analyses the filterbank in MP3 and AAC respectively, then explores the differences between them and gives some related experiments. The result shows that, compared with MP3, AAC shows a better coding efficiency and audio distortion control only in the filterbank module.

The Sign Bits of Huffman Codeword-Based Steganography for AAC Audio

A novel steganographic scheme within AAC bitstream is proposed in this paper. Based on the structure of AAC bitstream, the scheme hides secret information using the characteristics of the sign bits of Huffman codeword. The structure of original bitstream and the length of AAC file will not be changed after steganography. Experimental results are given to show that the proposed scheme has high capacity, good imperceptibility, and certain undetectability.

A novel detection scheme for MP3Stego with low payload

MP3Stego is a typical steganographic tool of MP3 audios. Though many researchers have been making every effort on attacking it, the performance of their approaches could be improved especially at the low embedding rate. In this paper, we have proposed a scheme for detecting low embedding rate of MP3Stego. Based on investigating the embedding principle of MP3Stego and observing the alteration of quantized MDCT coefficients (QMDCTs), the one-step transition probabilities of the difference of quantized MDCT coefficients were extracted. Finally, SVM was used for constructing a classification model according to the extracted features. Experimental results show that our scheme can effectively detect the MP3Stego steganography with low payload.

A multipurpose audio aggregation watermarking based on multistage vector quantization

Watermarking technology can achieve multipurpose such as copyright protection, copy protection, and integrity authentication. We propose a novel watermarking approach which involves robust watermark and fragile watermark in a two-stage quantization technique. Traditional watermarking algorithms mostly have poor performance in imperceptibility as the codeword selected from the modified codebook is not optimal. In our method, we select the codeword in the original codebook to ensure optimality. Furthermore, we use Huffman encoding to pick up property which is sensitive to many attacks in the entire aggregation. For copyright protection, the proposed scheme can resist attacks such as lossy compression, noise addition, and normalization. As for content authentication, the proposed scheme is sensitive to various attacks provided by Stirmark Benchmark for Audio. Experimental results show that the proposed method can be used respectively for protecting the copyright and authenticating the integrity of the audio aggregation.

Source Cell-Phone Identification Using Spectral Features of Device Self-noise

Source cell-phone identification has become a hot topic in multimedia forensics recently. In this paper, we propose a novel cell-phone identification method based on the recorded speech files. Device self-noise is considered as the fingerprint of the cell-phone, and the self-noise is estimated from the near-silent segments of recording. Moreover, two categories of spectral features of self-noise, i.e., spectral shape features (SN-SSF) and spectral distribution features (SN-SDF), are extracted for closed-set classification using SVM classifier. Experimental results show that the self-noise has the ability to identify the cell-phones of 24 different models, and identification accuracies of 89.23% and 94.53% have been obtained for SN-SSF and SN-SDF, respectively. To the best of our knowledge, it is the first attempt to comprehensively define the self-noise of cell-phone and furthermore apply it to source identification issue of audio forensics.

Audio Tampering Detection Based on Quantization Artifacts

MP3 is one of the common formats in the recording equipments. The authenticity and integrity of MP3 audio is widely concerned. We analyzed quantization characteristic of MP3 encoding, and studied the effect of quantified in frame offset and non offset frame. Then we combined statistical characteristics of zero spectral coefficients before and after quantization. Finally, a tampering detection method based on quantitative characteristics is proposed. According to the disadvantage of existing frame offset method that cannot detect high rate compression, this paper in the quantization artifacts description according to the characteristics of the line frequency distribution used in front of the 16 band. We can further effectively solve tamper detection problem of high bit rate compression by studying 16 band quantization. The experimental results show that the accuracy rate of proposed detection method can reach up to 99 %, the compression rate of detection can reach 256 Kbps, and the complexity of compared with the existing methods is significantly reduced.