In this study, a perceptual encryption algorithm is proposed for H.264/AVC video to enhance the scrambling effect and encryption space. Six new scan orders are designed for H.264/AVC encoder by analysing the energy distribution of discrete cosine transform coefficients. They are proven to have similar performance as the conventional zigzag scan order and its symmetrical scan order. These six new scan orders are combined with two existing scan orders to design a scan-order based perceptual encryption algorithm. Specifically, video encryption is achieved more specifically by randomly selecting one scan order from the eight scan orders with a security key, and the sign bit flipping of DC coefficients is also incorporated to further increase the encryption space. Experimental results show that the proposed approach has the advantages of both low bitrate increase and low computational cost. Furthermore, it is more flexible and has stronger security than the existing scan-order based video encryption schemes.

In this study high-performance and high-speed field-programmable gate array (FPGA) implementations of polynomial basis Itoh–Tsujii inversion algorithm (ITA) over GF(2 ^m ) constructed by irreducible trinomials and pentanomials are presented. The proposed structures are designed by one field multiplier and k -times squarer blocks or exponentiation by 2 ^k , where k is a small positive integer. The k -times squarer blocks have an efficient tree structure with low critical path delay, and the multiplier is based on a proposed high-speed digit-serial architecture with minimum hardware resources. Furthermore, to reduce the computation time of ITA, the critical path of the circuit is broken to finer path using several registers. The computation times of the structure on Virtex-4 FPGA family are 0.262, 0.192 and 0.271 µs for GF(2¹⁶³), GF(2¹⁹³) and GF(2²³³), respectively. The comparison results with other implementations of the polynomial basis Itoh–Tsujii inversion algorithm verify the improvement in the proposed architecture in terms of speed and performance.

The authors describe a method for producing Boolean functions of degree d ≥ 3 in n = 2dk − 1 (k = 1,  2,  …) variables, such that the functions are plateaued and balanced, have high nonlinearity and have no linear structures. The nonlinearity is 2 ⁿ⁻¹ − 2^(n−1)/2, which is the same as the largest possible nonlinearity for a quadratic function in n (odd) variables (the so-called ‘quadratic bound’). Their theorem uses some new ideas to generalise a theorem, which gave the case d = 3, in a 2009 paper by Fengrong Zhang et al. They discuss the cryptographic properties and applications for the functions.

In recent years, some research used classical and heavyweight encryption technology to realise data privacy and integrity protection in data aggregation of wireless sensor networks. The challenge is the balance between resource constraints and the complexity of the deployment. In this study, the authors proposed a lightweight and integrity-protecting oriented data aggregation scheme for wireless sensor networks (LIPDA) which has lightweight, secure and easy operability to preserve data privacy and integrity during data aggregation in wireless sensor network. First, a distance-based formation scheme of network topology is presented to balance the energy consumption of cluster heads. Then, a structure of complex number, which composes from the private factor of the nodes and the original data, is composed. The complex number is encrypted by additive homomorphic encryption method, which can realise the data aggregation without any decryption. Also, the reliability of data is ensured by using integrity verification method based on the complex operation. The theoretical analysis and simulation results show that the proposed scheme LIPDA can meet the requirement of privacy protection. Moreover, compared with related work, LIPDA has lower calculation, less traffic, higher accuracy and verifiable completeness.

This study concentrates on finding all truncated impossible differentials in substitution–permutation networks (SPNs) ciphers. Instead of using the miss-in-the-middle approach, the authors propose a mathematical description of the truncated impossible differentials. First, they prove that all truncated impossible differentials in an r + 1 rounds SPN cipher could be obtained by searching entry ‘0’ in D ( P ) ^r , where D ( P ) denotes the differential pattern matrix (DPM) of P-layer, thus the length of impossible differentials of an SPN cipher is upper bounded by the minimum integer r such that there is no entry ‘0’ in D ( P ) ^r . Second, they provide two efficient algorithms to compute the DPMs for both bit-shuffles and matrices over GF(2 ⁿ ). Using these tools they prove that the longest truncated impossible differentials in SPN structure is 2-round, if the P-layer is designed as an maximum distance separable (MDS) matrix. Finally, all truncated impossible differentials of advanced encryption standard (AES), ARIA, AES-MDS, PRESENT, MAYA and Puffin are obtained.

This study presents several meet-in-the-middle attacks on reduced-round Crypton and mCrypton block ciphers. Using the generalised δ-set, the authors construct 5-round distinguishers on Crypton and mCrypton. Based on these distinguishers, the authors propose meet-in-the-middle attacks on 8-round Crypton and mCrypton-96/128. The attack on Crypton needs 2¹²¹ chosen plaintexts, 2¹³² encryptions and 2¹³⁰ 128-bit blocks; the attacks on mCrypton need 2⁶¹ chosen plaintexts, 2⁸⁰ encryptions and 2⁷⁸ 64-bit blocks. Furthermore, the attack can be extended to 9 rounds for mCrypton-128 with complexities of 2⁶¹ chosen plaintexts, 2¹¹² encryptions and 2⁸² 64-bit blocks.

Recent network architectures utilise many types of security appliances to combat blended attacks. However, managing multiple separate security appliances can be overwhelming, inefficient and expensive. Thus, multiple security features are needed to be integrated into unified security architecture resulting in an unified threat management system (UTM). In most current UTM systems, whenever a security feature is needed, the corresponding module is just ‘attached or added on’. This approach of adding on may reduce the UTM performance dramatically, especially when security features such as IDS/IPS are enabled. In this study, a hybrid mechanism is proposed to solve UTM redundant packet classification problem. The mechanism is based on the use of splay tree filters and pattern-matching algorithms to enhance packet filtering and deep packet inspection (DPI) performance. The proposed mechanism uses network traffic statistics to dynamically optimise the order of the splay tree filters, allowing early acceptance and rejection of network packets. In addition, DPI signature rules are reordered according to their matching frequencies, allowing early packets acceptance. The authors demonstrate the merit of their mechanism through simulations performed on firewall and snort as independent packet manipulation systems compared with the proposed hybrid mechanism that uses unified communication between them.

Lattice problems are considered as the key elements in many areas of computer science as well as in cryptography; the most important of which is the shortest vector problem and its approximate variants. Algorithms for this problem are known as lattice reduction algorithms. Currently, the most practical lattice reduction algorithm for such problems is the block Korkine–Zolotarev (BKZ) algorithm and its variants. The authors optimise both the pruning and the preprocessing parameters of the recursive (aborted, extreme pruned) preprocessing of the BKZ lattice reduction algorithm and improve the results from Asiacrypt'11 by Chen and Nguyen. The authors derive approximate closed-form complexity formulas (based on the sandpile model assumption model by Hanrot et al.) for the enumeration time which allow a simple estimation of complexity without running the simulation algorithm (by Chen and Nguyen) and asymptotically suggests a modified extreme pruning bounding profiles with different parameters. Hence, the authors’ contributions are in optimising and improving the analysis of the complexity upper bound estimates presented by Chen and Nguyen, based on the same recursive-BKZ preprocessing model.