Browsing by Author "Hu, CM"

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A new approach for visual cryptography
(2002-12-01)
Tzeng, WG
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Hu, CM
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資訊工程學系
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Department of Computer Science
Visual cryptography is to encrypt a secret image into some shares (transparencies) such that any qualified subset of the shares can recover the secret "visually." The conventional definition requires that the revealed secret images are always darker than the backgrounds. We observed that this is not necessary, in particular, for the textual images. In this paper, we proposed an improved definition for visual cryptography based on our observation, in which the revealed images may be darker or lighter than the backgrounds. We studied properties and obtained bounds for visual cryptography schemes based on the new definition. We proposed methods to construct visual cryptography schemes based on the new definition. The experiments showed that visual cryptography schemes based on our definition indeed have better pixel expansion in average.
Compatible ideal contrast visual cryptography schemes with reversing
(2005)
Hu, CM
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Tzeng, WG
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資訊工程學系
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Department of Computer Science
Recently, Viet and Kurosawa proposed a VCS with reversing, which is a Visual Cryptography Scheme(VCS) where every participant OF is allowed to change black pixels on the transparency to white pixels and vice-versa. The contrast of their scheme is almost ideal, depending on the number of the reconstruction runs performed. Before long, S. Cimato et al. proposed two VCSs with reversing where the contrast of the reconstructed secret image is ideal. However, both Cimato et al.'s schemes cannot be decrypted solely with the human eye. In this paper we propose a new ideal VCS with reversing which is compatible and requires less stacking and reversing operations compared to all previous schemes. Each participant is required to store only two transparencies to reconstruct the ideal contrast secret image.
Inter-protocol interleaving attacks on some authentication and key distribution protocols
(1999-03-26)
Tzeng, WG
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Hu, CM
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資訊工程學系
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Department of Computer Science
We present a new attack, called the inter-protocol interleaving attack, on authentication and key distribution protocols. The attack enlightens us two things. The first is that when considering attacks against a protocol, we should consider not only the protocol itself, but also the interaction with other protocols. The second is about a warning of "not using the shared secret keys between a server and its clients in any other places" that appears in many security-related communication standards, such as CCITT X.509 and ISO 9798. Our attack provides a concrete example for showing that this warning is necessary. (C) 1999 Elsevier Science B.V. All rights reserved.
Modeling the floating-body effects of fully depleted, partially depleted, and body-grounded SOI MOSFETs
(2004-06-01)
Chan, M
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Su, P
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Wan, H
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Lin, CH
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Fung, SKH
This paper describes a unified framework to model the floating-body effects of various SOI MOSFET operation modes, including body-contacted mode, partially depleted mode and fully depleted mode. As the operation mode is dimension and bias dependent, different modes can co-exist in a single SOI technology. A smooth transit from one type of operation mode to another is thus essential and has been included in the model. In addition, the floating-body effects can couple to a number of other SOI specific phenomena such as heating assisted impact ionization, gate tunneling induced dynamic behavior, and operation mode dependent small signal output resistance. A methodology to model the overall SOI MOSFET behavior due to the combination of multiple floating-body related effects will also be described. (C) 2004 Published by Elsevier Ltd.
Novel dual-metal gate technology using Mo-MoSix combination
(2006-06-01)
Li, TL
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Ho, WL
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Chen, HB
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Wang, HCH
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Chang, CY
A novel dual-metal gate technology that uses a combination of Mo-MoSix gate electrodes is proposed. An amorphous-Si/Mo stack was fabricated as a gate electrode for the n-channel device. It was thermally annealed to form MoSix. Pure Mo served as the gate electrode for the p-channel device. The work functions of MoSix and pure Mo gates on SiO2 are 4.38 and 4.94 eV, respectively, which are appropriate for devices with advanced transistor structures. The small increase in the work function (< 20 meV) and the negligible equivalent oxide thickness variation (< 0.08 nm) after rapid thermal annealing at 950 degrees C for 30 s also demonstrate the excellent thermal stabilities of Mo and MoSix on SiO2. Additional arsenic ion implantation prior to silicidation was demonstrated further to lower the work function of MoSix to 4.07 eV. This approach for modulating the work function makes the proposed combination of Mo-MoSix gate electrodes appropriate for conventional bulk devices. The developed dual-metal-gate technology on HfO2 gate dielectric was also evaluated. The effective work functions of pure Mo and undoped MoSix gates on HfO2 are 4.89 and 4.34 eV, respectively. A considerable work-function shift was observed on the high-k. gate dielectric. The effect of arsenic preimplantation upon the work function of the metal silicide on HfO2 was also demonstrated, even though the range of modulation was a little reduced.