http://www.hindawi.comThe latest articles from Hindawi Publishing Corporation© 2008, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/GetArticle.aspx?doi=10.1155/2008/803217Spread-spectrum watermarking is generally considered to be robust against collusion attacks, and thereby suitable for digital fingerprinting. We have previously introduced the minority extreme attack (IWDW '07), and showed that it is effective against orthogonal fingerprints. In this paper, we show that it is also effective against random Gaussian fingerprint. Furthermore, we develop new randomised attacks which counter the effect of the decoder preprocessing of Zhao et al.Hans Georg Schaathun© 2008, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/GetArticle.aspx?doi=10.1155/2008/345184The use of digital watermarking in real applications is impeded by the weakness of current available algorithms against signal processing manipulations leading to the desynchronization of the watermark embedder and detector. For this reason, the problem of watermarking under geometric attacks has received considerable attention throughout recent years. Despite their importance, only few classes of geometric attacks are considered in the literature, most of which consist of global geometric attacks. The random bending attack contained in the Stirmark benchmark software is the most popular example of a local geometric transformation. In this paper, we introduce two new classes of local desynchronization attacks (DAs). The effectiveness of the new classes of DAs is evaluated from different perspectives including perceptual intrusiveness and desynchronization efficacy. This can be seen as an initial effort towards the characterization of the whole class of perceptually admissible DAs, a necessary step for the theoretical analysis of the ultimate performance reachable in the presence of watermark desynchronization and for the development of a new class of watermarking algorithms that can efficiently cope with them.Angela D'Angelo, Mauro Barni, and Neri Merhav© 2008, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/GetArticle.aspx?doi=10.1155/2008/895174We discuss a robust image authentication scheme based on a hash string constructed from leading JPEG2000 packet data. Motivated by attacks against the approach, key-dependency is added by means of employing a parameterized lifting scheme in the wavelet decomposition stage. Attacks can be prevented effectively in this manner and the security of the scheme in terms of unicity distance is assumed to be high. Key-dependency however can lead to reduced sensitivity of the scheme. This effect has to be compensated by an increase of the hash length which in turn decreases robustness.Gerold Laimer and Andreas Uhl© 2008, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/GetArticle.aspx?doi=10.1155/2007/78943The processing and encryption of multimedia content are generally considered sequential and independent operations. In certain multimedia content processing scenarios, it is, however, desirable to carry out processing directly on encrypted signals. The field of secure signal processing poses significant challenges for both signal processing and cryptography research; only few ready-to-go fully integrated solutions are available. This study first concisely summarizes cryptographic primitives used in existing solutions to processing of encrypted signals, and discusses implications of the security requirements on these solutions. The study then continues to describe two domains in which secure signal processing has been taken up as a challenge, namely, analysis and retrieval of multimedia content, as well as multimedia content protection. In each domain, state-of-the-art algorithms are described. Finally, the study discusses the challenges and open issues in the field of secure signal processing.Zekeriya Erkin, Alessandro Piva, Stefan Katzenbeisser, R. L. Lagendijk, Jamshid Shokrollahi, Gregory Neven, and Mauro Barni© 2008, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/GetArticle.aspx?doi=10.1155/2007/82790Alessandro Piva and Stefan Katzenbeisser© 2008, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/GetArticle.aspx?doi=10.1155/2008/195238Multimedia fingerprinting, also known as robust or perceptual hashing, aims at representing multimedia signals through compact and perceptually significant descriptors (hash values). In this paper, we examine the probability of collision of a certain general class of robust hashing systems that, in its binary alphabet version, encompasses a number of existing robust audio hashing algorithms. Our analysis relies on modelling the fingerprint (hash) symbols by means of Markov chains, which is generally realistic due to the hash synchronization properties usually required in multimedia identification. We provide theoretical expressions of performance, and show that the use of M-ary alphabets is advantageous with respect to binary alphabets. We show how these general expressions explain the performance of Philips fingerprinting, whose probability of collision had only been previously estimated through heuristics.Neil J. Hurley, Félix Balado, and Guénolé C. M. Silvestre© 2008, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/GetArticle.aspx?doi=10.1155/2007/98374We propose a joint encryption and compression (JEC) scheme with emphasis on application to video data. The proposed JEC scheme uses the philosophy of distributed source coding with side information to reduce the complexity of the compression process and at the same time uses cryptographic principles to ensure that security is built into the scheme. The joint distributed compression and encryption is achieved using a special class of codes called high-diffusion (HD) codes that were proposed recently in the context of joint error correction and encryption. By using the duality between channel codes and Slepian-Wolf coding, we construct a joint compression and encryption scheme that uses these codes in the diffusion layer. We adapt this cipher to MJPEG2000 with the inclusion of minimal amount of joint processing of video frames at the encoder.M. A. Haleem, K. P. Subbalakshmi, and R. Chandramouli© 2008, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/GetArticle.aspx?doi=10.1155/2007/56365A novel syntax-compliant encryption primitive and an efficient syntax-compliant JPEG 2000 encryption scheme are presented in this paper. The syntax-compliant encryption primitive takes, as input, syntax-compliant plaintext and produces syntax-compliant ciphertext. It is faster than all the other syntax-compliant encryption primitives we know. Our JPEG 2000 encryption scheme encrypts independently either each codeblock segment (normal mode) or each intersection of a codeblock segment and a codeblock contribution to a packet (in situ mode). Truncation-invariant parameters uniquely identifying each independently encrypted data block are combined with a global initialization vector to generate on the fly an initialization vector (IV) used to encrypt the data block. These IVs can be correctly regenerated even when the encrypted codestream is truncated. Encrypted codestreams are syntax-compliant. The original granularity of scalability is fully preserved after encryption so that an encrypted codestream can be truncated to adapt to different representations without decryption. Our JPEG 2000 encryption scheme is fast, error-resilient, and has negligible file-size overhead.Yang Yang, Bin B. Zhu, Shipeng Li, and Nenghai Yu© 2008, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/GetArticle.aspx?doi=10.1155/2007/19824Enrico Magli and Qibin Sun© 2008, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/GetArticle.aspx?doi=10.1155/2007/64521The first break our watermarking system (BOWS) contest challenged researchers to remove the watermark from three given images. Participants could submit altered versions of the images to an online detector. For a successful attack, the watermark had to be unreadable to this detector with a quality above 30 dB peak signal-to-noise ratio. We implemented our experiments in R, a language for statistical computing. This paper presents the BOWS package, an extension for R, along with examples for using this experimental environment. The BOWS package provides an offline detector for several platforms. Furthermore, the particular watermarking algorithm used in the contest is analysed. We show how to find single coefficient attacks and derive high-quality images (62.6 dB PSNR) with full knowledge of the key.Andreas Westfeld© 2008, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/GetArticle.aspx?doi=10.1155/2007/94565JPEG2000 encryption has become a widely discussed topic and quite a number of contributions have been made. However, little is known about JPEG2000 compression parameters and their influence on the security and performance of format, compliant encryption schemes. In this work, a thorough analysis of this topic is presented with a focus on format-compliant packet body encryption as sketched in the FCD 15444-8 (JPSEC). A proof for the reversibility of JPSEC format-compliant packet body encryption is given. As format-compliant packet body encryption preserves the JPEG2000 headers, which severely compromises the security, we additionally discuss packet header encryption with a special focus on format compliance and the influence of compression parameters on these schemes.Dominik Engel, Thomas Stütz, and Andreas Uhl© 2008, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/GetArticle.aspx?doi=10.1155/2007/45731Zero-knowledge watermark detectors presented to date are based on a linear correlation between the asset features and a given secret sequence. This detection function is susceptible of being attacked by sensitivity attacks, for which zero-knowledge does not provide protection. In this paper, an efficient zero-knowledge version of the generalized Gaussian maximum likelihood (ML) detector is introduced. This detector has shown an improved resilience against sensitivity attacks, that is empirically corroborated in the present work. Two versions of the zero-knowledge detector are presented; the first one makes use of two new zero-knowledge proofs for absolute value and square root calculation; the second is an improved version applicable when the spreading sequence is binary, and it has minimum communication complexity. Completeness, soundness, and zero-knowledge properties of the developed protocols are proved, and they are compared with previous zero-knowledge watermark detection protocols in terms of receiver operating characteristic, resistance to sensitivity attacks, and communication complexity.Juan Ramón Troncoso-Pastoriza and Fernando Pérez-González© 2008, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/GetArticle.aspx?doi=10.1155/2007/32028An objective performance measure is proposed to evaluate the intelligibility of a speech signal having its frequency subbands permuted. The proposed tool can be used to generate efficient keys for frequency domain scramblers as well as to assess the results of cryptanalysis.A. M. C. R. Borzino, J. A. Apolinário Jr., and D. G. da Silva© 2008, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/GetArticle.aspx?doi=10.1155/2007/25308From December 15, 2005 to June 15, 2006, the watermarking community was challenged to remove the watermark from 3 different 512×512 watermarked images while maximizing the peak signal-to-noise ratio (PSNR) measured by comparing the watermarked signals with their attacked counterparts. This challenge, which bore the inviting name of Break Our Watermarking System (BOWS), had as its main objective to enlarge the current knowledge on attacks to watermarking systems. In this paper, the main results obtained by the authors when attacking the BOWS system are presented and compared with strategies followed by other groups. Essentially, two different approaches have been followed: exhaustive search of the secret key and blind sensitivity attacks.Pedro Comesaña and Fernando Pérez-González© 2008, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/GetArticle.aspx?doi=10.1155/2007/13801Processing encrypted signals requires special properties of the underlying encryption scheme. A possible choice is the use of homomorphic encryption. In this paper, we propose a selection of the most important available solutions, discussing their properties and limitations.Caroline Fontaine and Fabien Galand© 2008, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/GetArticle.aspx?doi=10.1155/2007/43034The Break Our Watermarking System (BOWS) contest gave researchers three months to defeat an unknown watermark, given three marked images and online access to a watermark detector. The authors participated in the first phase of the contest, defeating the mark while retaining the highest average quality among attacked images. The techniques developed in this contest led to general methods for reverse-engineering a watermark algorithm via experimental images fed to its detector. The techniques exploit the tendency of watermark algorithms to admit characteristic false positives, which can be used to identify an algorithm or estimate certain parameters.Scott Craver, Idris Atakli, and Jun Yu© 2008, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/GetArticle.aspx?doi=10.1155/2007/51368One of the most important problems facing any distributed application over a heterogeneous network is the protection of private sensitive information in local terminals. A subfield of cryptography called secure multiparty computation (SMC) is the study of such distributed computation protocols that allow distrusted parties to perform joint computation without disclosing private data. SMC is increasingly used in diverse fields from data mining to computer vision. This paper provides a tutorial on SMC for nonexperts in cryptography and surveys some of the latest advances in this exciting area including various schemes for reducing communication and computation complexity of SMC protocols, doubly homomorphic encryption and private information retrieval.S.-C. S. Cheung and Thinh Nguyen© 2008, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/GetArticle.aspx?doi=10.1155/2007/31340Fingerprinting is an essential tool to shun legal buyers of digital content from illegal redistribution. In fingerprinting schemes, the merchant embeds the buyer's identity as a watermark into the content so that the merchant can retrieve the buyer's identity when he encounters a redistributed copy. To prevent the merchant from dishonestly embedding the buyer's identity multiple times, it is essential for the fingerprinting scheme to be anonymous. Kuribayashi and Tanaka, 2005, proposed an anonymous fingerprinting scheme based on a homomorphic additive encryption scheme, which uses basic quantization index modulation (QIM) for embedding. In order, for this scheme, to provide sufficient security to the merchant, the buyer must be unable to remove the fingerprint without significantly degrading the purchased digital content. Unfortunately, QIM watermarks can be removed by simple attacks like amplitude scaling. Furthermore, the embedding positions can be retrieved by a single buyer, allowing for a locally targeted attack. In this paper, we use robust watermarking techniques within the anonymous fingerprinting approach proposed by Kuribayashi and Tanaka. We show that the properties of an additive homomorphic cryptosystem allow for creating anonymous fingerprinting schemes based on distortion compensated QIM (DC-QIM) and rational dither modulation (RDM), improving the robustness of the embedded fingerprints. We evaluate the performance of the proposed anonymous fingerprinting schemes under additive-noise and amplitude-scaling attacks.J. P. Prins, Z. Erkin, and R. L. Lagendijk© 2008, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/GetArticle.aspx?doi=10.1155/2007/35262This work investigates the problem of efficient multimedia data encryption. A novel methodology is proposed to achieve encryption by controlling certain operations in the data compression process using a secret key. The new encryption approach consists of two cascaded modules. The first one is called randomized entropy coding (REC) while the second one is called rotation in partitioned bitstream (RPB). By leveraging the structure of the entropy coder, the joint REC/RPB encryption scheme incurs extremely low computational and implementation costs. Security analysis shows that the proposed scheme can withstand the ciphertext-only attack as well as the known/chosen plaintext attack. The efficiency and security of the proposed encryption scheme makes it an ideal choice in secure media applications where a large amount of multimedia data has to be encrypted/decrypted in real time.Dahua Xie and C.-C. Jay Kuo© 2008, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/GetArticle.aspx?doi=10.1155/2007/48179This paper analyzes the robustness properties of 2D chaotic map image encryption schemes. We investigate the behavior of such block ciphers under different channel error types and find the transmission error robustness to be highly dependent on on the type of error occurring and to be very different as compared to the effects when using traditional block ciphers like AES. Additionally, chaotic-mixing-based encryption schemes are shown to be robust to lossy compression as long as the security requirements are not too high. This property facilitates the application of these ciphers in scenarios where lossy compression is applied to encrypted material, which is impossible in case traditional ciphers should be employed. If high security is required chaotic mixing loses its robustness to transmission errors and compression, still the lower computational demand may be an argument in favor of chaotic mixing as compared to traditional ciphers when visual data is to be encrypted.Michael Gschwandtner, Andreas Uhl, and Peter Wild© 2008, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/GetArticle.aspx?doi=10.1155/2007/75961This paper describes an audio watermarking scheme based on sinusoidal signal modeling. To embed a watermark in an original signal (referred to as a cover signal hereafter), the following steps are taken. (a) A short-time Fourier transform is applied to the cover signal. (b) Prominent spectral peaks are identified and removed. (c) Their frequencies are subjected to quantization index modulation. (d) Quantized spectral peaks are added back to the spectrum. (e) Inverse Fourier transform and overlap-adding produce a watermarked signal. To decode the watermark, frequencies of prominent spectral peaks are estimated by quadratic interpolation on the magnitude spectrum. Afterwards, a maximum-likelihood procedure determines the binary value embedded in each frame. Results of testing against lossy compression, low- and highpass filtering, reverberation, and stereo-to-mono reduction are reported. A Hamming code is adopted to reduce the bit error rate (BER), and ways to improve sound quality are suggested as future research directions.Yi-Wen Liu and Julius O. Smith© 2008, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/GetArticle.aspx?doi=10.1155/2007/98684The break our watermarking system (BOWS) contest was launched in the framework of the activities carried out by the European Network of Excellence for Cryptology ECRYPT. The aim of the contest was to investigate how and when an image watermarking system can be broken while preserving the highest possible quality of the content, in the case the watermarking system is subject to a massive worldwide attack. The great number of participants and the echo that the contest has had in the watermarking community contributed to make BOWS a great success. From a scientific point of view, many insights into the problems attackers have to face with when operating in a practical scenario have been obtained, confirming the threat posed by the sensitivity attack, which turned out to be the most successful attack. At the same time, several interesting modifications of such an attack have been proposed to make it work in a real scenario under limited communication and time resources. This paper describes how the contest has been designed and analyzes the general progress of the attacks during the contest.A. Piva and M. Barni© 2008, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/GetArticle.aspx?doi=10.1155/2007/79048We introduce the concept of joint source coding, channel coding, and secrecy. In particular, we propose two practical joint schemes: the first one is based on error-correcting randomized arithmetic codes, while the second one employs turbo codes with compression, error protection, and securization capabilities. We provide simulation results on ideal binary data showing that the proposed schemes achieve satisfactory performance; they also eliminate the need for external compression and ciphering blocks with a significant potential computational advantage.Enrico Magli, Marco Grangetto, and Gabriella Olmo© 2008, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/GetArticle.aspx?doi=10.1155/2007/52965A novel encryption model for digital videos is presented. The model relies on the encryption-compression duality of certain types of permutations acting on video frames. In essence, the proposed encryption process preserves the spatial correlation and, as such, can be applied prior to the compression stage of a spatial-only video encoder. Several algorithmic modes of the proposed model targeted for different application requirements are presented and analyzed in terms of security and performance. Experimental results are generated for a number of standard benchmark sequences showing that the proposed method, in addition to providing confidentiality, preserves or improves the compression ratio.Daniel Socek, Spyros Magliveras, Dubravko Ćulibrk, Oge Marques, Hari Kalva, and Borko Furht© 2008, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/GetArticle.aspx?doi=10.1155/2007/37343The problem of secure data processing by means of a neural network (NN) is addressed. Secure processing refers to the possibility that the NN owner does not get any knowledge about the processed data since they are provided to him in encrypted format. At the same time, the NN itself is protected, given that its owner may not be willing to disclose the knowledge embedded within it. The considered level of protection ensures that the data provided to the network and the network weights and activation functions are kept secret. Particular attention is given to prevent any disclosure of information that could bring a malevolent user to get access to the NN secrets by properly inputting fake data to any point of the proposed protocol. With respect to previous works in this field, the interaction between the user and the NN owner is kept to a minimum with no resort to multiparty computation protocols.C. Orlandi, A. Piva, and M. Barni© 2008, Hindawi Publishing Corporation. All rights reserved.