High speed decoding of the binary (47, 24, 11) quadratic residue code

An efficient table lookup decoding algorithm (TLDA) is presented to decode up to five possible errors in a binary systematic (47, 24, 11) quadratic residue (QR) code. The main idea of the TLDA is based on the weight of syndrome, the syndrome decoder together with a reduced-size lookup table (RSLT), and the shift-search method given by Reed et al. Thus, the size of the lookup table and computational complexity in a finite field can be significantly reduced. The memory size of the proposed condensed lookup table (CLT) consists of only 36.6 Kbytes and is only about 0.24% of the full lookup table (FLT) and 3.2% of the lookup up table given by Chen et al., respectively. These facts lead to significant reduction of computational time and the decoding complexity. A simulation result shows that the decoding speed of the proposed TLDA is much faster than all existing decoding algorithms. Moreover, it can be extended to decode all QR codes, including the class of the cyclic codes when the code length is moderate. The CLT makes this new decoding algorithm suitable for hardware or firmware implementations.     

On the decoding of the (24, 12, 8) Golay code

An improved syndrome shift-register decoding algorithm, called the syndrome-weight decoding algorithm, is proposed for decoding three possible errors and detecting four errors in the (24, 12, 8) Golay code. This method can also be extended to decode two other short codes, such as the (15, 5, 7) cyclic code and the (31, 16, 7) quadratic residue (QR) code. The proposed decoding algorithm makes use of the properties of cyclic codes, the weight of syndrome, and the syndrome decoder with a reduced-size lookup table (RSLT) in order to reduce the number of syndromes and their corresponding coset leaders. This approach results in a significant reduction in the memory requirement for the lookup table, thereby yielding a faster decoding algorithm. Simulation results show that the decoding speed of the proposed algorithm is approximately 3.6 times faster than that of the algebraic decoding algorithm.     

Open Mobile Alliance (OMA) security layer: Architecture, implementation and performance evaluation of the integrity unit

Security has become a very critical issue in the provision of mobile services. The Open Mobile Alliance (OMA) has specified a powerful security layer, the WTLS. In this paper, a VLSI architecture for the implementation of the WTLS integrity unit is proposed. The proposed architecture is reconfigurable in the sense that operates in three different modes: as Keyed-Hash Authentication Code (HMAC), as SHA-1 and MD5 hash functions, according to WTLS specifications. This multi-mode operation is achieved due to the reconfigurable applied design technique in the proposed architecture, which keeps the allocated area resources at a minimized level. The proposed architecture achieves high speed performance, due to the pipeline designed architecture. Especially, SHA-1 operation achieved throughput is equal to 1,7 Gbps, while MD5 operation mode bit rate is equal to 2,1 Gbps. The proposed architecture has been integrated by using VHDL and has been synthesized placed and routed in an FPGA device. Comparisons with related hash functions implementations have been done in terms of throughput, operating frequency, allocated area and Area-Delay product. The achieved performance of the SHA-1 operation mode is better at about 14–42 times compared with the other conventional works. In addition, MD5 performance is superior to the other works at about 6–18 times, in all of the cases. The proposed Integrity Unit is a very trustful and powerful solution for the WTLS layer. In addition, it can be integrated in security systems which are used for the implementation networks for wireless protocols, with special needs of integrity in data transmission. Nicolas Sklavos, Ph.D.: He is a Ph.D. Researcher with the Electrical and Computer Engineering Department, University of Patras, Greece. His interests include computer security, new encryption algorithms design, wireless communications and reconfigurable computing. He received an award for his Ph.D. thesis on “VLSI Designs of Wireless Communications Security Systems” from IFIP VLSI SOC 2003. He is a referee of International Journals and Conferences. He is a member of the IEEE, the Technical Chamber of Greece and the Greek Electrical Engineering Society. He has authored or co-authored up to 50 scientific articles in the areas of his research. Paris Kitsos, Ph.D.: He is currently pursuing his Ph.D. in the Department of Electrical and computer Engineering, University of Patras, Greece. He received the B.S. in Physics from the University of Patras in 1999. His research interests include VLSI design, hardware implementations of cryptography algorithms, security protocols for wireless communication systems and Galois field arithmetic implementations. He has published many technical papers in the areas of his research. Epaminondas Alexopoulos: He is a student of the Department of Electrical and Computer Engineering, University of Patras, Greece. His research includes hardware implementations, mobile computing and security. He has published papers in the areas of his research. Odysseas Koufopavlou, Ph.D.: He received the Diploma of Electrical Engineering in 1983 and the Ph.D. degree in Electrical Engineering in 1990, both from University of Patras, Greece. From 1990 to 1994 he was at the IBM Thomas J. Watson Research Center, Yorktown Heights, NY, USA. He is currently an Associate Professor at the Department of Electrical and Computer Engineering, University of Patras. His research interests include VLSI, low power design, VLSI crypto systems and high performance communication subsystems architecture and implementation. He has published more than 100 technical papers and received patents and inventions in these areas.     

Visualizing references to off-screen content on mobile devices: A comparison of Arrows, Wedge, and Overview + Detail

When navigating large information spaces on mobile devices, the small size of the display often causes relevant content to shift off-screen, greatly increasing the difficulty of spatial tasks such as planning routes or finding points of interest on a map. Two possible approaches to mitigate the problem are Contextual Cues, i.e. visualizing abstract shapes in the border region of the view area to function as visual references to off-screen objects of interest, and Overview + Detail, i.e., simultaneously displaying a detail view and a small-scale overview of the information space. In this paper, we compare the effectiveness of two different Contextual Cues techniques, Wedge (Gustafson et al., 2008) and Scaled Arrows (Burigat et al., 2006), and a classical Overview + Detail visualization that highlights the location of objects of interest in the overview. The study involved different spatial tasks and investigated the scalability of the considered visualizations, testing them with two different numbers of off-screen objects. Results were multifaceted. With simple spatial tasks, no differences emerged among the visualizations. With more complex spatial tasks, Wedge had advantages when the task required to order off-screen objects with respect to their distance from the display window, while Overview + Detail was the best solution when users needed to find those off-screen objects that were closest to each other. Finally, we found that even a small increase in the number of off-screen objects negatively affected user performance in terms of accuracy, especially in the case of Scaled Arrows, while it had a negligible effect in terms of task completion times.     

Gibbs2: A new version of the quasiharmonic model code. II. Models for solid-state thermodynamics, features and implementation

In the second article of the series, we present the Gibbs2 code, a Fortran90 reimplementation of the original Gibbs program [Comput. Phys. Commun. 158 (2004) 57] for the calculation of pressure–temperature dependent thermodynamic properties of solids under the quasiharmonic approximation. We have taken advantage of the detailed analysis carried out in the first paper to implement robust fitting techniques. In addition, new models to introduce temperature effects have been incorporated, from the simple Debye model contained in the original article to a full quasiharmonic model that requires the phonon density of states at each calculated volume. Other interesting novel features include the empirical energy corrections, that rectify systematic errors in the calculation of equilibrium volumes caused by the choice of the exchange-correlation functional, the electronic contributions to the free energy and the automatic computation of phase diagrams. Full documentation in the form of a user?s guide and a complete set of tests and sample data are provided along with the source code.

Program summary

Program title:Gibbs2Catalogue identifier: AEJI_v1_0Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEJI_v1_0.htmlProgram obtainable from: CPC Program Library, Queen?s University, Belfast, N. IrelandLicensing provisions: GNU General Public License, v3No. of lines in distributed program, including test data, etc.: 936 087No. of bytes in distributed program, including test data, etc.: 8 596 671Distribution format: tar.gzProgramming language: Fortran90Computer: Any running Unix/LinuxOperating system: Unix, GNU/LinuxClassification: 7.8External routines: Part of the minpack, pppack and slatec libraries (downloaded from www.netlib.org) are distributed along with the program.Nature of problem: Given the static E(V) curve, and possibly vibrational information such as the phonon density of states, calculate the equilibrium volume and thermodynamic properties of a solid at arbitrary temperatures and pressures in the framework of the quasiharmonic approximation.Additional comments: A detailed analysis concerning the fitting of equations of state has been carried out in the first part of this article, and implemented in the code presented here.Running time: The tests provided only take a few seconds to run.     

Understanding buyers' loyalty to a C2C platform: the roles of social capital,satisfaction and perceived effectiveness of e‐commerce institutional mechanisms

Drawing upon social capital theory, this study aims to investigate how different dimensions of social capital affect online buyers' satisfaction and ultimately boost their loyalty to a Consumer‐to‐Consumer (C2C) platform. Specifically, we propose that three dimensions of social capital (i.e., cognitive, structural and relational capital) contribute positively to the two types of online buyers' satisfaction (i.e., economic and social satisfaction). In addition, we posit that perceived effectiveness of e‐commerce institutional mechanisms (PEEIM) moderates the relationships between economic and social satisfaction and buyers' loyalty to the platform. Three hundred buyers on the Consumer‐to‐Consumer platform, TaoBao, were surveyed to test the proposed model. The results suggest that buyers' evaluation of social capital with the community of sellers can enhance their satisfaction with the sellers, which subsequently affect their loyalty to the platform. Furthermore, perceived effectiveness of e‐commerce institutional mechanisms negatively moderates the effect of economic satisfaction and positively moderates the effect of social satisfaction on buyers' loyalty to the platform. The theoretical contributions and practical implications are discussed.