• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2012년도 춘계학술대회 논문집
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• pp.723-724
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• 2012

• Journal of Information Processing Systems
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• 제12권2호
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• pp.249-262
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• 2016

In 2004, Yang et al. proposed a threshold proxy signature scheme that efficiently reduced the computational complexity of previous schemes. In 2009, Hu and Zhang presented some security leakages of Yang's scheme and proposed an improvement to eliminate the security leakages that had been pointed out. In this paper, we will point out that both Yang and Hu's schemes still have some security weaknesses, which cannot resist warrant attacks where an adversary can forge valid proxy signatures by changing the warrant $m_w$. We also propose two secure improvements for these schemes.

• 소성∙가공
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• 제18권6호
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• pp.444-447
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• 2009

Piston crown to the hot forge a unified nature of the product has a shape with multi-level step forging process, so if you are not a mechanical professional, this process could lead to a significant loss to the material. Therefore, material technology in minor terms; continue to improve the collection rate that undamaged the product material. The piston crown and the manufacturing products such as marine diesel engines are being forged to reduce costs and to improve mechanical properties. Piston crown molding is a hot forging process that works in large volume forging products. Because of the size of the hard plastic material flow process for improving the design and actual field experience through advanced plastic technology, it is important to interpret the results. Also for many experimental plastic procedures, the accumulation of results is very important.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2009년도 추계학술대회 논문집
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• pp.89-92
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• 2009

As a class of materials, Ni-base superalloys are among the most difficult metal alloys to forge together with refractory metals and cobalt-base superalloys. The mechanical properties of Ni-base superalloys depend very much on grain size and the strengthening phases, $\gamma$' ($Ni_3$(Al,Ti)-type) and $\gamma$".($Ni_3$Nb-type). Especially, the control of grain size remains as a sole means for the control of mechanical properties. The grain size and distribution changes of the wrought superalloys during hot working and heat treatment are mainly controlled by the recrystallization and grain growth behaviors. In this presentation, prediction technology of grain size through the computer-aided process design, and numerical modeling for predicting the microstructure evolution of Ni-base superalloy during hot working were introduced. Also, some case studies were dealt with actual forming processes of Ni-base superalloys.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2009년도 추계학술대회 논문집
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• pp.379-381
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• 2009

In designing full vehicle, crash safety, fuel efficiency, exhaust gas, and driving stability are very important factors. Especially, automotive wheel which supports total vehicle weight is a critical component in view of driving stability. Most of automotive wheel have been manufactured for beautiful appearance by using aluminum alloy in domestic industry. However, the amount of automotive steel wheel used are on an increasing trend according to developing the advanced high strength steel with good formability property recently. In this study, the circumferential deviation of rim with various thickness and yield strength was investigated. The formability evaluation of the rim was developed by using a finite element module furnished by Forge software.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2009년도 춘계학술대회 논문집
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• pp.98-101
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• 2009

Piston crown to the hot forge a unified nature of the product has a shape with multi-level step forging process, so if you are not a mechanical process that can be a significant loss is material. Therefore, minor in terms of material technology; continue to improve the collection rate should be. The Piston crown and the manufacturing of products such as marine diesel engines, reducing costs and to improve mechanical properties of the method are being forged. Piston crown molding hot forging process the large volume forging products handling because of the size of the size of the hard plastic material flow process for improving the design and actual field experience through advanced plastic technology, and it is important to interpret the results and for many experimental plastic The accumulation of results is very important.

• 정보통신설비학회논문지
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• 제8권2호
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• pp.53-56
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• 2009

Kim et al. recently proposed an identity-based aggregate signature scheme to construct a secure routing protocol in ad-hoc networks. In this note, we unfortunately show that the identity-based aggregate signature scheme is universally forgeable, that is, anyone can forge the signature of any messages of its choice. This subsequently means that their secure routing protocol is not secure.

• 소성∙가공
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• 제18권6호
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• pp.453-457
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• 2009

In this paper, plastic deformation behaviors of ESW105 and SCM435 steels are revealed by simulations and experiments. ESW105 is the special pre-heat-treated steel characterized by high initial yield strength and negligible strain-hardening behavior. The flow stresses of the two steels for large stain are calculated from tensile tests. Axial and lateral compressions of cylindrical bars are tested and simulated and the deformed shapes are compared to characterize the plastic deformation behaviors of the two materials. A forward extrusion process of a cylindrical bar is also simulated to reveal the difference. It has been shown that there are pretty much difference in plastic flow between ESW105 and SCM435 which causes from the difference in strain-hardening capability, implying that the experience-oriented design rules for common commercial materials may lead to failure in process design when the new material of ESW105 is applied without consideration of its plastic deformation behavior.

• 정보보호학회논문지
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• 제19권6호
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• pp.17-22
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• 2009

인증서 없는 공개키 시스템은 기존의 공개키 암호시스템에서 인증서의 필요성을 제거하고 신원 기반 암호시스템에서 키 위탁 문제를 해결하였다. 본 논문에서는 Guo 등과 Wang 등에 의해서 제안된 각각의 인증서 없는 서명 기법들이 공격자 종류 I에 의해 키 대치공격에 취약하다는 것을 보인다. 다시 말해, 서명자의 공개키를 대치할 수 있는 능력을 가진 공격자가 서명자의 비밀키를 알지 못함에도 불구하고 서명을 위조할 수 있음을 보이고 이러한 공격을 방지하기 위한 대응법을 제안한다.

• 정보처리학회논문지C
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• 제16C권1호
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• pp.21-26
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• 2009

최근 소비자들의 다양한 요구로 인하여 IPTV에 대한 수요가 폭발적으로 증가하고 있다. IPTV는 트리플 플레이(음성, 인터넷, 비디오)를 소비자에게 전달하며, IP 컨버젼스 네트워크의 킬러 어플리케이션으로 주목 받고 있다. IPTV는 서비스 공급자의 이익을 위하여 수신자 접근 제어 수단으로 CAS를 이용한다. 현재 CAS는 수신자 인증을 통하여 접근 제어를 제공하지만, 서비스 공급자로부터 전달되는 컨텐츠에 대해서는 어떠한 인증도 제공하지 않는다. 그러므로, 공격자가 서비스 공급자로부터 전달되는 컨텐츠를 조작하여 해로운 정보를 수신자에게 전달할 수 있는 보안 취약점이 존재한다. 본 논문은 해쉬 트리 스킴에 기반하여 현재 IPTV 시스템의 취약점을 제거하는 효율적이고 강력한 소스 인증 프로토콜을 제안한다. 또한, IPTV의 요구사항 관점에서 제안한 프로토콜을 평가한다.