This special issue comprises of fourteen selected papers from the International Symposium on Electronic Commerce Security (ISECS 2009), Nanchang, China, 22-24 May 2009. The conference received 1050 paper submissions from 19 countries and regions, of which 487 were selected for presentation after a rigorous review process. From these 487 research papers, through two rounds of reviewing, the guest editors selected twelve as the best papers on the Computers track of the Conference. The candidates of the Special Issue are all the authors, whose papers have been accepted and presented at the ISECS 2009 and WISA 2009, with the contents not been published elsewhere before. The ISECS 2009 and WISA 2009 are sponsored by Nanchang HangKong University, China, Peoples' Friendship University of Russia, Nanchang University (China), Jiangxi Normal University (China), Wuhan University (China), National Chung Hsing University (Taiwan), Institute of Software, Chinese Academy of Sciences, Sichuan University (China), and Jiaxing University (China). Technical Co-Sponsors of the conference are IEEE, IEEE Computer Society, and IEEE Computer Society Technical Committee on E-Commerce. “Lossless Compression Schemes of Vector Quantization Indices Using State Codebook”, by Chin-Chen Chang, Guei-Mei Chen, Chia-Chen Lin, proposes two novel schemes to further compress the VQ index table of images based on the SOC scheme without losing any image quality by the original VQ encoding. Simulation results indicate that the proposed schemes achieve significant reduction of bit rate without losing any image quality by the original VQ encoding. “Assuring Structural Parallel Programs based on Scoped Permissions”, by Yang Zhao, Ligong Yu, Gongxuan Zhang, proposes a "scoped permission" system for a simple object-oriented language with sharedmemory and structural parallelism. The permission is abstracted as a linear value associated with some piece of state in a program and it is normally adopted in program analysis and verification. “Empirical Study on the Influence of Social Capital to Informal Knowledge Transfer among Individuals”, by Zhihong Li, Tao Zhu. Based on theories of knowledge transfer, the hypotheses of influence of social capital to informal knowledge transfer among individuals were proposed. By empirical study, this paper verified and revised the model, and revealed that three dimensions of social capital not only have a direct significant effect on informal knowledge transfer performance among individuals, but also have an indirect effect on the informal knowledge transfer performance among individuals by impacting on knowledge transfer opportunities, motives and ability respectively. “An Improved Ant Colony Optimization Cluster Algorithm Based on Swarm Intelligence”, by Weihui Dai, Shouji Liu and Shuyi Liang, proposes an improved ant colony optimization cluster algorithm based on a classics algorithm - LF algorithm. By the introduction of a new formula and the probability of similarity metric conversion function, as well as the new formula of distance, this algorithm can deal with the category data easily. This algorithm can handle large category dataset more rapidly, accurately and effectively, and keep the good scalability at the same time..........