Abstract Since multimedia data are now more widely distributed in digital form and easier to copy and change, copyright protection has become an essential need. One of the most common copyright protection techniques is watermarking. Invisibility and robustness are crucial aspects of watermarking; however, many of the currently used techniques simply focus more on invisibility than how robust they are. Moreover, the trade-off between invisibility and robustness is challenging. To this end, this paper proposes a novel watermark technique that efficiently overcomes the idea of a trade-off between robustness and invisibility, thereby increasing both under most attacks. Schur decomposition and a dynamic weighting factors matrix are added to the embedding process to improve the robustness of the proposed technique. Besides that, the embedding function is improved to simultaneously maximize imperceptibility and robustness. Another key contribution of the proposed approach is its use of a trajectory-based optimization algorithm rather than the more prevalent population-based algorithms to determine the optimal scaling factors. Consequently, the proposed technique rapidly identifies the best scaling factors for the embedding function. Statistical analysis is performed using the Friedman test. Experimental results show that the proposed technique outperforms other existing techniques for different sizes, shapes, and types of watermarks.

Abstract For many wireless sensor networks applications, a powerful localization algorithm is required to determine the exact positions of sensor nodes. In this paper, a new localization algorithm is presented which combines the distance vector hop (DV-Hop) algorithm with the shuffled shepherd optimization algorithm to determine the position for each unknown node within 3-D space. Studying the localization problem in 3-D space is more realistic, but more challenging due to the enlarged search space. Comparison of our proposed algorithm with its alternatives in literature shows that it offers improved accuracy and more stable performance with respect to changes in nodes density and communication range.

Two new encryption algorithms for secure video transmission are proposed in this paper. The two algorithms employ different types of chaotic maps to generate the keystream for encrypting the video frames. Both algorithms involve a substitution step and a permutation step to achieve confusion and diffusion requirements. For efficient transmission, the video file is compressed before being encrypted. In the basic implementation of both algorithms, MPEG‐2 standard is used for compression. However, the algorithms are shown to be compliant with other compression techniques. In the permutation step, the effect of the block size used in the shuffling process is examined. Smaller blocks result in increasing the processing time, while reducing both the correlation between adjacent pixels and the peak‐signal‐to noise ratio of an encrypted frame. The use of a Feistel structure is investigated to enhance security and its negative impact on the encryption time is demonstrated. The experimental results of the two proposed schemes confirm that they represent different tradeoffs between security and computational efficiency. Both schemes are sensitive to slight variations in the encryption key as apparent from the obtained differential measures. The conducted comparative study shows the competitiveness of the proposed schemes to existing schemes in literature.

Managing large personal image databases requires efficient privacy preserving indexing methods to allow for their outsourcing to possibly curious cloud servers. To construct a secure inverted index in this paper, first, visual words are extracted from stored images based on the Speeded‐Up and Robust Features (SURF). Next, Order Preserving Encryption (OPE) is used to encipher the frequencies of occurrence of the extracted visual words. Another scale and rotation invariant feature, which is the local HSV histogram, is included for comparison. From the obtained results, it is apparent that SURF achieves more precise results. Aggregation of both features is considered to further improve the accuracy. The effects of the weighting scheme of the visual words and their number on the performance are investigated. Weighted term frequency inverse document frequency (tf‐idf) together with the Jaccard similarity measure yield the best performance. OPE encryption is shown to have minor impact on the retrieval accuracy. To reduce encryption time, a lookup table is constructed. The inverted index reduces the search time significantly compared to a sequential search scheme as apparent from the results. A comparative study with recent related schemes demonstrates the competitiveness of the implemented system in terms of computational efficiency and accuracy.

This paper blends the ideas from recent researches into a simple, yet efficient image encryption scheme for colored images. It is based on the finite field cosine transform (FFCT) and symmetric-key cryptography. The FFCT is used to scramble the image yielding an image with a uniform histogram. The FFCT has been chosen as it works with integers modulo p and hence avoids numerical inaccuracies inherent to other transforms. Fractals are used as a source of randomness to generate a one-time-pad keystream to be employed in enciphering step. The fractal images are scanned in zigzag manner to ensure decorrelation of adjacent pixels values in order to guarantee a strong key. The performance of the proposed algorithm is evaluated using standard statistical analysis techniques. Moreover, sensitivity analysis techniques such as resistance to differential attacks measures, mean square error, and one bit change in system key have been investigated. Furthermore, security of the proposed scheme against classical cryptographic attacks has been analyzed. The obtained results show great potential of the proposed scheme and competitiveness with other schemes in literature. Additionally, the algorithm lends itself to parallel processing adding to its computational efficiency.

Cognitive radio (CR) is a technology that aims to enhance the use of the underutilized spectrum. Spectrum handoff plays this role by allowing the unlicensed secondary users (SUs) to use the licensed frequency bands of the primary users (PUs). Moreover, it helps the SU to vacate the channel at the presence of the PU and find a suitable channel for the interrupted SU to continue his unfinished transmission. In this paper, an analytical model for the general case of non-identical channels in CR networks is introduced for both fixed and probabilistic sequence approaches for target channel selection. Moreover, a new balancing model is suggested to generate the probabilistic sequence. Both the fixed and probabilistic sequence approaches are optimized using the meta-heuristic methods of particle swarm and genetic algorithm in the seek of finding an optimal approach to minimize the extended data delivery time of the SUs. The results are based on the pre-emptive resume priority M/M/1 queueing network model and are shown for different network cases. Based on the optimization results, a fast hybrid approach is proposed and found to achieve near optimal solution.

Publishing digital content covered by intellectual property or copyright is faced by the challenge of countering illegal access to the digital good, while still enabling consumers to exercise their usage rights on purchased contents. Digital rights management (DRM) systems consist of architectures, protocols and technologies aimed at providing satisfactory solutions to the above problem. Trace and revoke schemes present one attractive cryptographic solution. This paper presents a scalable trace and revoke scheme that enables users verify their secret keys and thus protects them against corrupt ones due to malicious distributors or errors in communications. Moreover, the scheme is scalable supporting an unlimited number of revocations. Furthermore, the users secret keys are renewed which makes the task of external adversaries and traitors more difficult. In addition, broadcast messages are secure against chosen ciphertext attacks.

Anonymity of consumers is an essential functionality that should be supported in any digital rights management system. Privacy protection is an important aspect for wider acceptance of consumers of DRM systems. The concept of a blind signature is one possible cryptographic solution, yet it has not received much attention in the identity-based setting. In the identity-based setting, the public key of a user is derived from his identity, thus simplifying certificates management process compared to traditional public key cryptosystems. In this paper, a new blind identity-based signature scheme based on bilinear pairings on elliptic curves is presented. The use of bilinear pairings over elliptic curves enables utilizing smaller key sizes, while achieving the same level of security compared to other schemes not utilizing elliptic curves. The correctness of the proposed scheme is validated and the proof of the blindness property is provided. Performance and security related issues are addressed.