A Differential Cryptanalysis of Yen-Chen-Wu Multimedia Cryptography System (MCS)

At ISCAS'2005, Yen et al. presented a new chaos-based cryptosystem for multimedia transmission named "Multimedia Cryptography System" (MCS). No cryptanalytic results have been reported so far. This paper presents a differential attack to break MCS, which requires only seven chosen plaintexts. The complexity of the attack is O(N), where $N$ is the size of plaintext. Experimental results are also given to show the real performance of the proposed attack.Comment: 22 pages, 5 figure

The effects of goal orientations on knowledge management system usage, knowledge sourcing and learning outcome

This research investigates individual differences in the context of knowledge management system (KMS) usage, knowledge sourcing and learning outcome. Individual differences are measured for mastery, performance and avoidance goal orientations. Individuals with high mastery goal orientations prefer to master and develop new skills and knowledge. Those with high performance goal orientations prefer to compare their performances with others. Lastly, those with high avoidance goal orientations prefer to avoid a new task if they feel incompetent. User posting and reading activities in a KMS are examined over a 3- month period. Consistent with goal orientation theory, the results show that mastery goal orientation has an effect on reading, knowledge sourcing and learning outcome. In contrast, performance goal orientation has an effect only on posting, but not on reading. To a lesser degree than mastery goal orientation, avoidance goal orientation has an effect on reading, but not posting. These findings have important implications for both knowledge management researchers and practitioners

SEARCH AND PURCHASE IN INFORMATION-OVERLOADED RETAIL ELECTRONIC MARKETPLACE: DOES PRICE AND REPUTATIOIN MATTER?

This study explores buyers\u27 search and purchase behavior in an information-overloaded retail Electronic Marketplace (EMP). Two instrumental variables, i.e. number of visitors and number of sales for an item, are used to represent buyers\u27 search and purchase behavior. Price and reputation, two of the most frequently researched independent variables in EMP studies, are considered. The relationships between the two IVs and the two DVs are verified when transaction items are of search-type and of experience-type. This study is conducted using field data collected from Taobao (the most dominant retail EMP in China). It is found that reputation has consistent positive relationships with two DVs. Price has negative effects on two DVs. However, it might have no impacts in the case of experience-type items. Conclusively, in information overloaded EMP, reputation always matters in influencing buyers\u27 search and purchase behavior, while price only matters in the case of search-type items

Assessing Information Systems and Computer Information Systems Programs from a Balanced Scorecard Perspective

Assessment of educational programs is one of the important means used in academia for accountability, accreditation, and improvement of program quality. The assessment practices, guidelines, and requirements are very broad and vary widely among academic programs and from one institution to the other. In this paper, from the theoretical lenses of a strategic planning and management methodology, the Balanced Scorecard, we try to integrate various perspectives into a performance assessment framework for an educational assessment of computing and information systems. Particularly, based on the actual accreditation experience, we propose two assessment models: a conceptual model and a process model. This modeling approach addresses the critical conceptual elements required for educational assessment and provides practical guidelines to follow for a complete, smooth and successful assessment process. In addition, we present a set of robust tools and techniques, incorporated into the process steps, team work, and task-driven management process. We were successful in our accreditation efforts, and improved the quality of our computing and information systems programs by using these presented assessment methods. We share our views and thoughts in the form of lessons learned and suggested best practices so as to streamline program assessment and simplify its procedures and steps

Cryptanalysis of an Image Scrambling Scheme without Bandwidth Expansion

Recently, a novel image scrambling (i.e., encryption) scheme without bandwidth expansion was proposed based on two-dimensional (2-D)discrete prolate spheroidal sequences (DPSS). This paper gives a comprehensive cryptanalysis of the image scrambling scheme, and draw a conclusion that it is not sufficiently secure against various cryptographical attacks, including ciphertext-only attack, known/chosen-plaintext attack and chosen-ciphertext attack. The cryptanalytic results suggest that the image scrambling scheme can only be used to realize perceptual encryption, instead of provide content protection for digital images

A Study of an Outburst in the Classical Symbiotic Star Z And in a Colliding-Wind Model

Two-dimensional gas-dynamical modeling of the mass-flow structure is used to study the outburst development in the classical symbiotic star Z And. The stage-by-stage rise of the light during the outburst can be explained in the framework of the colliding winds model. We suggest a scenario for the development of the outburst and study the possible influence of the changes of the flow structure on the light of the system. The model variations of the luminosity due to the formation of a system of shocks are in good agreement with the observed light variations

Characterization of a human prothrombin gene enhancer

The 5' flanking sequence of the human prothrombin gene was isolated by screening a human liver phage library with a human prothrombin cDNA as a hybridization probe. A phage was identified that contained 3 kilobasepairs of DNA upstream of the initiator methionine codon. Primer extension studies showed that the major transcription initiation sites were located 23 and 36 basepairs upstream of the initiator codon. DNA sequences in the 5' flanking region of the human prothrombin gene were then analyzed for cis-activating transcriptional activity by a transient expression system using the human growth hormone gene as the reporter gene. The chimeric expression vector was introduced into HepG2 cells, and secreted human growth hormone was monitored by using a radioimmunoassay. These studies showed that the 3 kbp fragment contained sequences that were sufficient for the initiation of transcription in HepG2 cells. Subsequent deletion studies showed that the 3 kbp fragment contained two elements: a weak promoter in the region immediately upstream of the mRNA coding sequence, and an enhancer located between nucleotides -860 and -940. The enhancer element was active at a distance and in either orientation. In addition, the enhancer was liver cell specific, and acted on heterologous promoters including the herpes simplex virus thymidine kinase promoter and the mouse metallothionein I promoter. Comparison of the nucleotide sequence of the enhancer with a DNA sequence data base showed the enhancer sequence to be unique. The enhancer sequence is flanked by an inverted repeat, 5' CCTCCC 3', and contains a putative binding site for hepatic nuclear factor 1 (HNF-1). Deoxyribonuclease I footprint analysis and linker scanning mutagenesis showed that the enhancer contains multiple protein binding motifs. Mutagenesis of the 3' boundary CCTCCC sequence eliminated the enhancer activity. Comparison with other liver genes showed the presence of the CCTCCC sequence in the hepatitis B virus enhancer, the ⍺-1 antitrypsin promoter, and the fibrinogen (β-chain promoter, suggesting a functional role for this motif. Using the concatenated human prothrombin enhancer as a probe to screen a HepG2 expression library, a cDNA encoding for the Y-box binding protein was identified. A putative Y-box was also found in the enhancer region, suggesting that the protein factor may be partially responsible for the human prothrombin gene expression. Northern blot analysis using the Y-box binding protein cDNA as a probe indicated that the Y-box binding protein mRNA is expressed in all of the tested tissues. This protein may be one of the constitutively expressed transcription factors responsible for the regulation of a number of genes.Medicine, Faculty ofBiochemistry and Molecular Biology, Department ofGraduat

An analysis of some approximate inverse preconditioning for linear system

The class of preconditioning that approximates the inverse of the matrix A is studied in the thesis. We emphasize on investigating some variants of the approximate inverse (APINV) preconditioning. They are formed basically from minimizing the norm of the residual matrix R = I - MA. If Frobenius nom is chosen, it can be decoupled into N independent least square problem. Hence the construction of this preconditioner has a high degree of parallelism, which is suitable for massively parallel computations. Exact solve and multi-color approaches to the APINV preconditioner are discussed in the thesis. We apply the conventional and two-color Fourier analyses to these two approaches on model problem. We find that both approaches give smaller condition number and numerical experiments confirm the results. Setup costs and parallel implementations of the APINV preconditioners will also be discussed and analysed. In addition we compare two variable APINV preconditioners proposed by Huckle[l5] and Chow[5]. These two algorithms impose a variable sparsity pattern to the preconditioner. Analysis on setup costs and comments on parallel implementations are given. Numerical results are also presented on the comparison of these two approaches