A Fragile Zero Watermarking Scheme to Detect and Characterize Malicious Modifications in Database Relations

We put forward a fragile zero watermarking scheme to detect and characterize malicious modifications made to a database relation. Most of the existing watermarking schemes for relational databases introduce intentional errors or permanent distortions as marks into the database original content. These distortions inevitably degrade the data quality and data usability as the integrity of a relational database is violated. Moreover, these fragile schemes can detect malicious data modifications but do not characterize the tempering attack, that is, the nature of tempering. The proposed fragile scheme is based on zero watermarking approach to detect malicious modifications made to a database relation. In zero watermarking, the watermark is generated (constructed) from the contents of the original data rather than introduction of permanent distortions as marks into the data. As a result, the proposed scheme is distortion-free; thus, it also resolves the inherent conflict between security and imperceptibility. The proposed scheme also characterizes the malicious data modifications to quantify the nature of tempering attacks. Experimental results show that even minor malicious modifications made to a database relation can be detected and characterized successfully

Numerical and experimental investigation of the effect of process parameters on sheet deformation during the electromagnetic forming of AA6061-T6 alloy.

Electromagnetic forming is a high-speed sheet metal forming technique to form metallic sheets by applying magnetic forces. In comparison to the conventional sheet metal forming process, electromagnetic forming is a process with an extremely high velocity and strain rate, which can be effectively used for the forming of certain difficult-to-form metals. During electromagnetic forming, it is important to recognise the effects of process parameters on the deformation and sheet thickness variation of the sheet metal. This research focuses on the development of a numerical model for aluminium alloy (AA6061-T6) to analyse the effects of three process parameters, namely voltage, sheet thickness and number turns of the coils, on the deformation and thickness variation of the sheet. A two-dimensional fully coupled finite-element (FE) model consisting of an electrical circuit, magnetic field and solid mechanics was developed and used to determine the effect of changing magnetic flux and system inductance on sheet deformation. Experiment validation of the results was performed on a 28 KJ electromagnetic forming system. The Taguchi orthogonal array approach was used for the design of experiments using the three input parameters (voltage, sheet thickness and number of turns of the coil). The maximum error between numerical and experimental values for sheet thickness variation was observed to be 4.9 %. Analysis of variance (ANOVA) was performed on the experimental results. Applied voltage and sheet thickness were the significant parameters, while the number of turns of the coil had an insignificant effect on sheet deformation. The contribution ratio of voltage and sheet thickness was 46.21 % and 45.12 % respectively. The sheet deformation from simulations was found to be in good agreement with the experimental results

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京都大学0048新制・課程博士博士(情報学)甲第8573号情博第20号新制||情||3(附属図書館)UT51-2000-M37京都大学大学院情報学研究科システム科学専攻(主査)教授 英保 茂, 教授 金澤 正憲, 教授 松田 哲也学位規則第4条第1項該当Doctor of InformaticsKyoto UniversityDA