KEYWORDS: Digital watermarking, Feature extraction, Signal to noise ratio, Receivers, Quantization, Signal detection, Modulation, Correlation function, Linear filtering, Binary data
Speech content authentication, which is also called speech content integrity or tamper detection, protects the integrity of speech contents instead of the bitstream itself. In this work, two major approaches for flexible speech authentication are presented and compared. The first scheme is based on content feature extraction that is integrated with CELP speech coders to minimize the total computational cost. Speech features relevant to semantic meaning are extracted, encrypted and attached as the header information. The second method embeds fragile watermarks into the speech signal in the frequency domain. If the speech signal is tampered, the secret watermark sequence is also modified. The receiver detects the fragile watermark from received data and compares it to the original secret sequence. These two approaches are compared in terms of computational complexity, false detection rate, and tolerance to mis-synchronization and content preserving operations. It is shown that each approach has its own merits and shortcomings.
Efficient encryption algorithms are essential to multimedia data security, since the data size is large and real-time processing is often required. After discussing limitations of previous work on multimedia encryption, we propose a novel methodology for confidentiality, which turns entropy coders into encryption ciphers by using multiple statistical models. The choice of statistical models and the order in which they are applied are kept secret as the key Two encryption schemes are constructed by applying this methodology to the Huffman coder and the QM coder. It is shown that security is achieved without sacrificing the compression performance and the computational speed. The schemes can be applied to most modern compression systems such as MPEG audio, MPEG video and JPEG/JPEG2000 image compression.
Two methodologies for efficient audiovisual data encryption are studied in this research, i.e. selective encryption and MHT (multiple-Huffman-table). We first discuss benefits and limitations of selective encryption, and propose a selective encryption scheme for ITU G.723.1 speech coding. A review of all cryptanalysis work of selective encryption algorithms in the literature is given, our cryptanalysis for the JPEG/MPEG sign-bit encryption scheme is presented, and two rules to determine whether selective encryption for a compression system is suitable are concluded. Then, we investigate another encryption methodology via the manipulation of Huffman coding tables of multimedia coding systems. The MHT scheme chooses several different Huffman tables from a vast number of possible candidates, and uses them alternatively to encode multimedia data. The choice of Huffman tables and the order that they are used are kept secret as the key. This method requires very little computational overhead, and can be applied to the encryption of MPEG audio, MPEG video and JPEG/JPEG2000 images.
KEYWORDS: Digital watermarking, Data communications, Fourier transforms, Linear filtering, Wavelets, Distortion, Signal detection, Interference (communication), Algorithm development, Signal processing
Digital audio watermarking embeds inaudible information into digital audio data for the purposes of copyright protection, ownership verification, covert communication, and/or auxiliary data carrying. In this paper, we first describe the desirable characteristics of digital audio watermarks. Previous work on audio watermarking, which has primarily focused on the inaudibility of the embedded watermark and its robustness against attacks such as compression and noise, is then reviewed. In this research, special attention is paid to the synchronization attack caused by casual audio editing or malicious random cropping, which is a low-cost yet effective attack to watermarking algorithms developed before. A digital audio watermarking scheme of low complexity is proposed in this research as an effective way to deter users from misusing or illegally distributing audio data. The proposed scheme is based on audio content analysis using the wavelet filterbank while the watermark is embedded in the Fourier transform domain. A blind watermark detection technique is developed to identify the embedded watermark under various types of attacks.
A digital audio watermarking scheme of low complexity is proposed in this research as an effective way to deter users from misusing or illegally distributing audio data. Previous work on audio watermarking has primarily focused on the inaudibility of the embedded watermark and its robustness against attacks such as compression and noise. In this research, special attention is paid to the synchronization attack caused by casual audio editing or malicious random cropping, which is a low-cost yet effective attack to watermarking algorithms developed before. The proposed scheme is based on audio content analysis and watermark embedding in the Fourier transform domain. A blind watermark detection technique is developed to identify the embedded watermark under various types of attacks.
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