• Title/Summary/Keyword: the moon

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Cryptanalysis of the Randomized Signed-Scalar Multiplication (랜덤 부호화 스칼라 곱 알고리즘 분석)

  • 한동국;김태현;장상운;박영호
    • Proceedings of the Korea Institutes of Information Security and Cryptology Conference
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    • 2003.07a
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    • pp.83-88
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    • 2003

  • 부채널 공격(side channel attack)을 막는 새로운 접근방법으로 생각되는 랜덤 부호화 스칼라 곱 알고리즘은 Ha와 Moon에 의해서 제안되었다. 그러나 이 방법은 여전히 논쟁의 여지가 있다. 본 논문에서는 Ha-Moon 알고리즘이 기존의 세 가지 단순 전력 소모량 분석(simple power analysis, SPA)에 안전함을 보인다. 그리고 정수론의 성질을 이용하여 두 가지 중요한 정리를 제시하고 이 정리들을 이용하여 Ha-Moon 알고리즘에 적용할 수 있는 공격 알고리즘을 개발한다. 예를 들면, 163-비트 키들에 대하여 제안 알고리즘은 20개의 전력 소모량을 이용하여 키 복잡도 Ο(2$^{8}$ )를 가지고 공격할 수 있다.

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Analysis Distribution and Feature of Lunar Gravity Field Using SGM90d Model (SGM90d모델을 이용한 달 중력장 분포 및 특징 분석)

  • Huang, He;Yun, Hong-Sic;Lee, Dong-Ha
    • Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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    • v.27 no.2
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    • pp.129-138
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    • 2009

  • The lunar gravity field is an important source to understand the lunar interior structure, dichotomy and magma ocean of the moon, furthermore it can be used to study the origin and evolution history of the moon. In this paper, we firstly investigated the history of lunar exploration were performed for determining the lunar gravity field, in addition to investigating the procedure of progress related with the lunar gravity field model and gravity observations techniques. After, we determined practically the gravity anomalies of the moon using the new lunar gravity model, SGM90d (SELENE Gravity Model), which were developed by processing the tracking data from SELENE, the japanese lunar mission. Finally, we compared the lunar gravity anomalies from SGM90d model to the those from existing lunar gravity model (LP165P). As results from the comparison, we can make a sense that 4-way Doppler observations of SELENE is very effective to measure the gravity field on the farside of the moon. The precise lunar gravity field model including the farside of the moon which can be more helpful to understand the dichotomy of moon and to establish the detailed distribution of lunar gravity field, such as a mascon.

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Changes in Mechanical Properties of WC-Co by Ultrasonic Nanocrystal Surface Modification Technique (UNSM 기술을 이용한 초경의 기계적 특성변화)

  • Lee, Seung-Chul;Kim, Jun-Hyong;Kim, Hak-Doo;Choi, Gab-Su;Amanov, Auezhan;Pyun, Young-Sik
    • Tribology and Lubricants
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    • v.31 no.4
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    • pp.157-162
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    • 2015

  • In this study, an ultrasonic nanocrystalline surface modification (UNSM) technique is applied to tungsten carbide-cobalt (WC-Co) to extend the service life of carbide parts used in press mold. The UNSM technique modifies the structure, reduces the surface roughness, increases the surface hardness, induces the compressive residual stress, and increases the wear resistance of materials by introducing severe plastic deformation. The surface roughness, hardness, and compressive residual stress of WC after UNSM treatment improve by about 42, 10, and 71%, respectively. A wear test under dry conditions is used to assess the effectiveness of the UNSM technique on the friction and wear behavior of WC. The UNSM technique is found to reduce the WC friction coefficient by approximately 21% and enhance the wear resistance by approximately 85%. The improved friction and wear behavior of WC may be mainly attributed to the increased hardness and compressive residual stress. Moreover, the WC specimen is treated by UNSM technique using three different WC, silicon nitride (Si3N4) and stainless steel (STS304) balls. The surface treated by WC balls shows the highest hardness when compared with treatment by stainless steel and silicon nitride balls. According to the obtained results, the UNSM technique is believed to increase the durability of the carbide component by improving the friction and wear behavior.

  • https://doi.org/10.9725/kstle.2015.31.4.157 인용 PDF KSCI KPUBS HTML