Browsing by Author "Tsai, Hsin-Yi"

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A framework for quantitative evaluation of parallel control-flow obfuscation
(2012-11-01)
Huang, Yu-Lun
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Tsai, Hsin-Yi
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電控工程研究所
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Institute of Electrical and Control Engineering
Software obfuscation is intended to protect a program by thwarting reverse engineering. Several types of software obfuscation have been proposed, and control-flow obfuscation is a commonly adopted one. In this paper, we present a framework to evaluate parallel control-flow obfuscation, which raises difficulty of reverse engineering by increasing parallelism of a program. We also define a control flow graph of a program and some atomic operators for obfuscating transformations. The proposed framework comprises three phases: parsing, formalization and evaluation. A program is first parsed to a control flow graph. Then, we formalize a parallel control-flow obfuscating transformation based on our atomic operators. By selecting target code blocks in the control flow graph and applying obfuscating transformations to the target code blocks, the original program is then obfuscated. In the third phase, we define a measure to calculate the program complexity. The measure can be considered as a degree to which an obfuscating transformation can confuse a human trying to understand the obfuscated program. Such a measure can also be used as the base of the potency metric to estimate the capability of the obfuscated program against reverse engineering. Our novel framework helps efficiently examine a control-flow obfuscating transformation in a systematic manner and helps select an appropriate obfuscating transformation among a number of candidates to better protect a program. (C) 2012 Elsevier Ltd. All rights reserved.
A Graph Approach to Quantitative Analysis of Control-Flow Obfuscating Transformations
(2009-06-01)
Tsai, Hsin-Yi
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Huang, Yu-Lun
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Wagner, David
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電控工程研究所
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Institute of Electrical and Control Engineering
Modern obfuscation techniques are intended to discourage reverse engineering and malicious tampering of software programs. We study control-flow obfuscation, which works by modifying the control flow of the program to be obfuscated, and observe that it is difficult to evaluate the robustness of these obfuscation techniques. In this paper, we present a framework for quantitative analysis of control-flow obfuscating transformations. Our framework is based upon the control-flow graph of the program, and we show that many existing control-flow obfuscation techniques can be expressed as a sequence of basic transformations on these graphs. We also propose a new measure of the difficulty of reversing these obfuscated programs, and we show that our framework can be used to easily evaluate the space penalty due to the transformations.
An Analytic Hierarchy Process-Based Risk Assessment Method for Wireless Networks
(2011-12-01)
Tsai, Hsin-Yi
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Huang, Yu-Lun
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電控工程研究所
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Institute of Electrical and Control Engineering
This paper presents a wireless risk assessment method to help an administrator manage wireless network security. The assessment method consists of a risk model and an assessment measure. The risk model is in charge of modeling the wireless network risk. Security requirements, wireless attacks, and system configurations are considered in the model. The assessment measure is an algorithm which determines the risk value of the wireless network according to the risk model. Our risk model is developed upon an extended analytic hierarchy process, which contains the 4 layers: the risk layer, the requirement layer, the attack layer, and the configuration layer. The separate layers of the risk model are helpful in dealing with the dynamics of a wireless network because only the related layers are introduced to the assessment measure when changes of the network are detected. Based on the risk model per device, our assessment measure evaluates the wireless network risk in consideration of the relations between devices, attacks, and configurations. Hence, our risk assessment method, composed of the risk model and the assessment measure, can determine the wireless network risk efficiently while considering the dependencies in the wireless network. Two examples are introduced in this paper to examine the feasibility of our method. In the first example, we demonstrate that the risk values derived by our method meet the ground truth by performing practical experiments. The second example shows that our method can evaluate the risk of a changing wireless network with efficiency, and can distinguish disparities in different wireless networks.
Facet-Dependent Photocatalytic Behaviors of ZnS-Decorated Cu2O Polyhedra Arising from Tunable Interfacial Band Alignment
(2019-01-23)
Naresh, Gollapally
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Hsieh, Pei-Lun
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Meena, Vandana
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Lee, Shih-Kuang
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Chiu, Yi-Hsuan
ZnS particles were grown over Cu2O cubes, octahedra, and rhombic dodecahedra for examination of their facet-dependent photocatalytic behaviors. After ZnS growth, Cu2O cubes stay photocatalytically inactive. ZnS-decorated Cu2O octahedra show enhanced photocatalytic activity, resulting from better charge carrier separation upon photo excitation. Surprisingly, Cu2O rhombic dodecahedra give greatly suppressed photocatalytic activity after ZnS deposition. Electron paramagnetic resonance spectra agree with these experimental observations. Time-resolved photoluminescence profiles provide charge-transfer insights. The decrease in the photocatalytic activity is attributed to an unfavorable band alignment caused by significant band bending within the Cu2O(110)/ZnS(200) plane interface. A modified Cu2O-ZnS band diagram is presented. Density functional theory calculations generating plane -specific band energy diagrams of Cu2O and ZnS match well with the experimental results, showing that charge transfer across the Cu2O(110)/ZnS(200) plane interface would not happen. This example further illustrates that the actual photocatalysis outcome for semiconductor heterojunctions cannot be assumed because interfacial charge transfer is strongly facet-dependent.
Novel Supramolecular Side-Chain Banana-Shaped Liquid Crystalline Polymers Containing Covalent- and Hydrogen-Bonded Bent bores
(2010-02-09)
Wang, Ling-Yung
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Tsai, Hsin-Yi
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Lin, Hong-Cheu
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材料科學與工程學系
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Department of Materials Science and Engineering
Novel supramolecular side-chain banana-shaped liquid crystalline (LC) polymer complexes AmBn-N bearing various (m/n) molar ratios of hydrogen- and covalent-bonded bent-core components were acquired by the free radical polymerization, where the hydrogen-bonded (H-bonded) structures were executed via mixing equimolar portions of proton donor (H-donor) polymers AmBn (homopolymers/copolymers) and pyridyl proton acceptor (H-acceptor) bent cores (small molecules). The influences of the molar ratios of bent-core H-bonded components in side-chain banana-shaped LC polymers and their corresponding polymer complexes on mesomorphic and electro-optical properties were first investigated. The voltage-dependent antiferroelectric properties of spontaneous polarization (Ps) values in the polar smectic phase of the supramolecular side-chain banana-shaped copolymers were also reported. The nematic and tilted smectic phases were verified by XRD measurements, and the SmCp phase was further confirmed by the triangular wave method. Suprinsingly, a novel enantiotropic polar smectic (SmCP(A)) phase was generated in some bent-core side-chain polymer complexes AmBn-N. Therefore, a special approach to constructing (or stabilizing) the SmCP phase was first developed in this study by copolymerization of bent-core covalent - and H-bonded units in side-chain polymer complexes (with proper m/n molar ratios of 16/1 and 10/1 from both bent-core covalent- and H-bonded monomers (i.e., B and A-N units, respectively) without the SmCP phase.
Optical imaging with spectrum aberration correction using a filtering macrolens
(2013-07-20)
Lin, Yu-Hsuan
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Lai, Jyun-Yi
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Tsai, Hsin-Yi
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Chang, Han-Chao
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Huang, Hung Ji
A filtering macrolens was developed to simultaneously achieve macro-optical imaging and correct spectrum aberration. The macrolens was a doublet lens comprising a filtering lens and a close-up lens. The shape of the filtering lens was designed to eliminate the optical path differences between the light rays in the absorbing medium. The close-up lens was designed to decrease the effective focal length of an ordinary camera lens to provide high magnification capability and collimate the diverging beams through the filtering lens. Experimental results demonstrated that the spectrum uniformity of the macro-optical images was markedly improved by the filtering macrolens. This innovation may be used in finite conjugate optical systems. (C) 2013 Optical Society of America
Threat as a Service? Virtualization's Impact on Cloud Security
(2012-01-01)
Tsai, Hsin-Yi
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Siebenhaar, Melanie
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Miede, Andre
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Huang, Yu-Lun
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Steinmetz, Ralf
Understanding the physical and economic consequences of attacks on control systems
(2009-10-01)
Huang, Yu-Lun
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Cardenas, Alvaro A.
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Amin, Saurabh
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Lin, Zong-Syun
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Tsai, Hsin-Yi
"This paper describes an approach for developing threat models for attacks on control systems. These models are useful for analyzing the actions taken by an attacker who gains access to control system assets and for evaluating the effects of the attacker's actions on the physical process being controlled. The paper proposes models for integrity attacks and denial-of-service (DoS) attacks, and evaluates the physical and economic consequences of the attacks on a chemical reactor system. The analysis reveals two important points. First, a DoS attack does not have a significant effect when the reactor is in the steady state; however, combining the DoS attack with a relatively innocuous integrity attack rapidly causes the reactor to move to an unsafe state. Second, an attack that seeks to increase the operational cost of the chemical reactor involves a radically different strategy than an attack on plant safety (i.e., one that seeks to shut down the reactor or cause an explosion). (C) 2009 Elsevier B.V. All rights reserved."