Browsing by Author "Wu, Hsin-Lung"

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An Efficient Fragile Watermarking Scheme for Pixel-wise Tamper Detection
(2012)
Lee, Yang-Kuo
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Chang, Jen-Chun
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Wu, Hsin-Lung
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Chen, Rong-Jaye
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資訊工程學系
In this paper we propose a novel pixel-wise fragile watermarking scheme which is able to detect tampered pixels with very high probability. Based on a new technique called Image-Dependent Seed (IDS), the proposed method is not only efficient but also secure against many known attacks. Furthermore, the proposed scheme can be simply implemented with only bit-wise AND and Exclusive-OR operations.
Complexity of Hard-Core Set Proofs
(2011-03-01)
Lu, Chi-Jen
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Tsai, Shi-Chun
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Wu, Hsin-Lung
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資訊工程學系
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Department of Computer Science
We study a fundamental result of Impagliazzo (FOCS'95) known as the hard-core set lemma. Consider any function f : {0,1}(n) -> {0,1} which is "mildly hard", in the sense that any circuit of size s must disagree with f on at least a delta fraction of inputs. Then, the hard-core set lemma says that f must have a hard-core set H of density delta on which it is "extremely hard", in the sense that any circuit of size s' = O(s/1/epsilon(2) log 1/epsilon(delta)))) must disagree wiht f on at least (1 - epsilon)/2 fraction of inputs from H. There are three issues of the lemma which we would like to address: the loss of circuit size, the need of non-uniformity, and its inapplicability to a low-level complexity class. We introduce two models of hard-core set proofs, a strongly black-box one and a weakly black-box one, and show that those issues are unavoidable in such models. First, we show that using any strongly black-box proof, one can only prove the hardness of a hard-core set for smaller circuits of size at most s' = O(s/1/epsilon(2) log 1/delta)). Next, we show that any weakly black-box proof must be inherently non-uniform-to have a hard-core set for a class G of functions, we need to start from the assumption that f is hard against a non-uniform complexity class with Omega(1/epsilon log vertical bar G vertical bar) bits of advice. Finally, we show that weakly black-box proofs in general cannot be realized in a low-level complexity class such as AC (0)[p]-the assumption that f is hard for AC (0)[p] is not sufficient to guarantee the existence of a hard-core set.
Decoding permutation arrays with ternary vectors
(2011-10-01)
Lee, Chia-Jung
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Lin, Te-Tsung
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Shieh, Min-Zheng
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Tsai, Shi-Chun
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Wu, Hsin-Lung
We give an explicit decoding scheme for the permutation arrays under Hamming distance metric, where the encoding is constructed via a distance-preserving mapping from ternary vectors to permutations (3-DPM).
Highly accelerated stress method for measuring water vapor transmission rate of PV backsheet
(2019-01-01)
Wu, Hsin-Lung
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Lie, Yu-Tai
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Chen, Syh-Homg
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Hsieh, Chao-Fan
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Yu, Peichen
In this study, we investigate the water vapor transmission rate (WVTR) with highly accelerated stress test (HAST) for the backsheets of the photovoltaic module. According to the Fick's equation, the WVTR can be fitted by the water concentration of EVA with time dependence. In order to receive the trend of the relative humidity in the photovoltaic module, the flexible printed circuit with high accuracy humidity sensors were embedded in two ethylene-vinyl-acetate (EVA) stacks and laminated with glass and backsheet. Compare to result of the commercial method, this way can reach high accuracy in 3 cycles. However, we get the WVTR of backsheets using dry process in the open air space, but the inhomogeneous temperature and humidity cause the lower WVTR.
Hybrid Organic Silicon Solar Cells Using a Carbon-Nanotube Doped PEDOT:PSS Hole Selective Layer
(2019-01-01)
Kuo, Li-Jung
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Lee, Li-Yu
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Chiu, Chi-Lin
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Wu, Hsin-Lung
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Chen, Yan-Syun
In this work, we employ carbon nanotube (CNT) doped PEDOT:PSS to increase the conductivity and evaluate the potential of CNT-doped PEDOT:PSS as a hole selective layer for conventional silicon solar cell. Two types of PEDOT: PSS noted as TC100, TC200 with a relative high and low CNT concentrations. The results have shown that PEDOT: PSS could effectively passivate the silicon surface. The contact resistivity for holes is also smaller than that for electrons on a polished surface. Finally, conventional solar cells with a polished or textured rear surfaces are incorporated with the TC100 and TC200. The results shown that the PEDOT:PSS increase the open-circuit voltage, and short-circuit current, compared to the reference cell. A power conversion efficiency of 14.55% has been achieved for the device with the TC100 hole selective layer.
Hybrid PEDOT: PSS - Silicon Solar Cell Packaging Employing Ultrathin Transparent Conductive Films
(2018-01-01)
Wu, Ching-Wen
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Li, You-Lan
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Chiu, Chi-Lin
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Wu, Hsin-Lung
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Kitazawa, Hiroyuki
In this work, we demonstrate the packaging of hybrid organic - silicon solar cell mini-modules employing flexible and ultrathin transparent conductive films. The unique engineering plastic substrates are printed with high-resolution, micrometer-scaled silver meshes to achieve superior optical transmittance and low sheet resistance, offering the efficient collection of charged carriers through distributed metallic grids. The width of silver grid can be as low as 3 mu m, which is a 10 to 15 fold reduction compared to the conventional grid width used in screen printing. By systematically comparing various substrate materials and process conditions, we achieve a power conversion efficiency of 9.5% on 2x2 cm(2) mini-modules.
Impossibility results on weakly black-box hardness amplification
(2007)
Lu, Chi-Jen
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Tsai, Shi-Chun
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Wu, Hsin-Lung
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資訊工程學系
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Department of Computer Science
We study the task of hardness amplification which transforms a hard function into a harder one. It is known that in a high complexity class such as exponential time, one can convert worst-case hardness into average-case hardness. However, in a lower complexity class such as NP or sub-exponential time, the existence of such an amplification procedure remains unclear. We consider a class of hardness amplifications called weakly black-box hardness amplification, in which the initial hard function is only used as a black box to construct the harder function. We show that if an amplification procedure in TIME(t) can amplify hardness beyond an O(t) factor, then it must basically embed in itself a hard function computable in TIME(t). As a result, it is impossible to have such a hardness amplification with hardness measured against TIME(t). Furthermore, we show that, for any k is an element of N, if an amplification procedure in Sigma P-k can amplify hardness beyond a polynomial factor, then it must basically embed a hard function in Sigma P-k. This in turn implies the impossibility of having such hardness amplification with hardness measured against Sigma P-k/poly.
Improved hardness amplification in NP
(2007-02-12)
Lu, Chi-Jen
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Tsai, Shi-Chun
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Wu, Hsin-Lung
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資訊工程學系
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Department of Computer Science
We study the problem of hardness amplification in NP. We prove that if there is a balanced function in NP such that any circuit of size s(n) = 2(Omega(n)) fails to compute it on a 1/poly(n) fraction of inputs, then there is a function in NP such that any circuit of size s(n) fails to compute it on a 1/2 - 1/s'(n) fraction of inputs, with s'(n) = 2(Omega(n2/13)). This improves the result of Healy et al. (STOC'04), which only achievess s' (n) = 2(Omega(n1/2)) for the case with s(n) = 2(Omega(n)). (c) 2006 Elsevier B.V. All rights reserved.
On the complexity of hardness amplification
(2008-10-01)
Lu, Chi-Jen
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Tsai, Shi-Chun
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Wu, Hsin-Lung
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資訊工程學系
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Department of Computer Science
For delta is an element of (0, 1) and k, n is an element of N, we study the task of transforming a hard function f : {0, 1}(n) -> {0, 1}, with which any small circuit disagrees on (1 - delta)/2 fraction of the input, into a harder function f', with which any small circuit disagrees on (1 - delta(k))/2 fraction of the input. First, we show that such hardness amplification, when carried out in some black-box way, must require a high complexity. In particular, it cannot be realized by a circuit of depth d and size 2(o(k1/d)) or by a nondeterministic circuit of size o(k/log k) (and arbitrary depth) for any delta is an element of (0, 1). This extends the result of Viola, which only works when (1 - delta)/2 is small enough. Furthermore, we show that even without any restriction on the complexity of the amplification procedure, such a black-box hardness amplification must be inherently nonuniform in the following sense. To guarantee the hardness of the resulting function f', even against uniform machines, one has to start with a function f, which is hard against nonuniform algorithms with Omega(k log(1/delta)) bits of advice. This extends the result of Trevisan and Vadhan, which only addresses the case with (1 - delta)/2 = 2(-n). Finally, we derive similar lower bounds for any black-box construction of a pseudorandom generator (PRG) from a hard function. To prove our results, we link the task of hardness amplifications and PRG constructions, respectively, to some type of error-reduction codes, and then we establish lower bounds for such codes, which we hope could find interest in both coding theory and complexity theory.
On the construction of permutation arrays via mappings from binary vectors to permutations
(2006-08-01)
Huang, Yen-Ying
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Tsai, Shi-Chun
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Wu, Hsin-Lung
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資訊工程學系
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Department of Computer Science
An (n, d, k)-mapping f is a mapping from binary vectors of length n to permutations of length n + k such that for all x, y is an element of {0, 1}(n), d(H) (f (x), f (y)) >= d(H)(x, y) + d, if d(H) (x, y) <= (n + k)-d and d(H) (f (x), f (y)) = n + k, if d(H) (x, y) > (n + k)-d. In this paper, we construct an (n, 3, 2)-mapping for any positive integer n >= 6. An (n, r)-permutation array is a permutation array of length n and any two permutations of which have Hamming distance at least r. Let P (n, r) denote the maximum size of an (n, r)-permutation array and A (n, r) denote the same setting for binary codes. Applying (n, 3, 2)-mappings to the design of permutation array, we can construct an efficient permutation array (easy to encode and decode) with better code rate than previous results [Chang (2005). IEEE Trans inf theory 51:359-365, Chang et al. (2003). IEEE Trans Inf Theory 49:1054-1059; Huang et al. (submitted)]. More precisely, we obtain that, for n >= 8, P(n, r) >= A(n-2, r-3) > A(n-1, r-2) = A (n, r-1) when n is even and P(n, r) >= A(n-2, r-3) = A(n-1, r-2) > A(n, r-1) when n is odd. This improves the best bound A(n-1, r-2) so far [Huang et al. (submitted)] for n >= 8.
Simple distance-preserving mappings from ternary vectors to permutations
(2008-07-01)
Lin, Te-Tsung
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Tsai, Shi-Chum
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Wu, Hsin-Lung
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資訊工程學系
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Department of Computer Science
We give a simple construction of distance-preserving Mappings from ternary vectors to permutations (3-DPM). Our result gives a lower bound for permutation arrays, i.e., P(n, d) >= A(3)(n, d), which significantly improves previous lower bounds for d <= 3n/5.