• Bulletin of the Korean Mathematical Society
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• v.46 no.4
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• pp.803-819
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• 2009

In classical encryption schemes, data is encrypted under a single key that is associated with a user or group. In Ciphertext-Policy Attribute-Based Encryption(CP-ABE) keys are associated with attributes of users, given to them by a central trusted authority, and data is encrypted under a logical formula over these attributes. We extend this idea to the case where an arbitrary number of independent parties can be present to maintain attributes and their corresponding secret keys. We present a scheme for multi-authority CP-ABE, propose the first two constructions that fully implement the scheme, and prove their security against chosen plaintext attacks.

• Proceedings of the IEEK Conference
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• 2000.11b
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• pp.321-324
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• 2000

In this paper, we proposed a new visual cryptography scheme based on optical interference which improves the contrast and SNR of reconstructed images comparing with conventional visual cryptography method. We divided an binary image to be encrypted into n slides. To encrypt them, (n-1) random independent keys and one another random key by XOR process between four random keys were prepared. XOR between each divided image and each random key makes encrypted n encrypted images. From these images, encrypted binary phase masks can be made. For decryption all of phase masks should be placed together in the interferometer such as Mach-Zehnder interferometer.

• Proceedings of the IEEK Conference
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• 2000.11c
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• pp.69-72
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• 2000

In this paper, a novel algorithm for digital watermarking is proposed. We use two pattern keys from BCH (15, 7) code and one randomizing key. In the embedding process, optimal watermark coefficients are determined by statistical analysis of the DCT coefficients from the standpoint of HVS. In the detection, watermark coefficients are restored by correlation matching of the possible pattern keys and minimizing the estimation errors. Attacks tested in the experiments ate image enhancement and image compression (JPEG). Performance is evaluated by BER of the logo images and SNR/PSNR of the restored images. Our method has higher performance against JPEG attacks. Analysis for the performance is included.

• Korean Journal of Plant Taxonomy
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• v.32 no.4
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• pp.417-447
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• 2002

Polygonatum taxa of Korea were classified as two sections, three series and 14 species and 2 varieties and reviewed taxonomically. Among the examined taxa, endemics in Korea were recorded as two species; P. grandicaule Y. S. Kim, B. U. Oh & C. G. Jang and P. infundiflorum Y. S. Kim, B. U. Oh & C. G. Jang. The habitat of Korean unrecorded species, P. acuminatifolium Kom. and P. odoratum var. odoratum were confirmed in this study. Keys to the sections, series and species including description of each taxon were provided here.

• Proceedings of the IEEK Conference
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• 2001.06a
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• pp.269-272
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• 2001

Since Multi-way Search Tree reduces the number of the memory access by increasing the branch factor, it is considered a method to archive the high-speed IP address lookup. Using the combination of initial 16 bit may and Multi-way Search Tree, it also reduces the search time of If address lookup. Multi-way Search Tree consists of K keys and K＋1 key pointers. This paper shows how the E update of Multi-way Search Tree which consists of the one pointer within a node can be performed. Using the one pointer within a node, it increases the number of keys within a node and reduces the search time of IP lookup. We also describes IP updating methods such as modification, Insertion and Deletion of address entries. Our update scheme performs better than the method which rebuilds the entire IP routing table when IP update processes.

• Journal of the Korean Institute of Telematics and Electronics
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• v.17 no.2
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• pp.1-9
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• 1980

A voltage synthesizing channel selection circuit was designed to improve on the conventional vol tape synthesizer which has been memorized each charnel's tuning vol cage itself. In the course of this study, tuning voltage was calculated by channel number entered from 10 keys. Then this circuit has tie function of direct access channel selection and rear display of channel number for the whole range of UHF and VHF, Attention was also given to realize the fine tuning by searching each commended channel, and the sequential selection by using 2keys, and the flash of channel indicator in case of inactive station.

• Proceedings of the Korean Information Science Society Conference
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• 1999.10c
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• pp.285-287
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• 1999

블록 암호알고리즘에 대한 기존의 연산 모드들(ECB 또는 CBC 등)은, 각 블록에 대하여 동일한 키로 암호화를 수행한다. 이것은 침입자가 한번의 암호 요청만을 수행하여 많은 수의 평문/암호문 쌍을 얻을 수 있게 함으로써 차분해독법 등의 공격에는 안전성을 제공하지 않는다. 본 논문에서는 블록 암호 알고리즘을 위한 새로운 모드를 제안하는데, 이 모드에서는 암호화되는 각각의 블록이 서로 다른 키로 암호화되도록 함으로써 블록의 개수가 많아짐에 따라 안전성 면에서 상당한 이득을 얻게 된다. 각 블록을 위한 서로 다른 키를 생성하는 것이 추가 연산을 필요로 하지만, 제안하는 모드를 DES에 적용한 TDK(a mode for DEA with unTraceable Dynamic Keys)의 수행 시간을 pentium과 sun sparc 상에서 측정해 본 결과 ECB 모드와 거의 유사함을 알 수 있었다.

• Animal Systematics, Evolution and Diversity
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• v.24 no.2
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• pp.185-189
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• 2008

Two species of the chloroperlid stonefly, Alloperla medlata and Sweltsa illiesi, are reported for the first time in Korea. Alloperla mediata can be distinguished by the smaller epiproct and the presence of a median sclerite under epiproct in male, and by the modified subgenital plate in female. Sweltsa illiesi can be distinguished by the presence of a pair of ridges on tergum 9 in male and upward V-shaped pattern on the center of head in adults. The line drawings of diagnostic characters and taxonomic remarks of the two species are provided with keys and comparative characters for adults of Korean Chloroperlidae.

• Proceedings of the Korea Society for Industrial Systems Conference
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• 2008.10b
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• pp.445-448
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• 2008

The key establishment between nodes is one of the most important issues to secure the communication in wireless sensor networks. Some researcher used the probabilistic key sharing scheme with a pre-shared key pool to reduce the number of keys and the key disclosure possibility. However, there is a potential possibility that some nodes do not have a common share in the key pool. The purpose of this paper is to devise a peer to peer key sharing protocol (PPKP) based on Quorum system and Diffie-Hellman key exchange scheme (DHS). The PPKP establishes a session key by creating a shared key using the DHS and then scrambles it based on Quorum system to secure that. The protocol reduces the number of necessary keys than the previous schemes and could solve the non-common key sharing possibility problem in the probabilistic schemes.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.177-183
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• 2008

For 10 kW-class Stirling engine using scroll expander and scroll compressor, considerations on thermal expansion of the fixed and orbiting scroll members of the scroll expander due to high gas temperature at the expander inlet has resulted in adopting of the keys between the fixed scroll and main frame for the fixed scroll side and spring type insertion between the orbiting scroll base plate and supporting holders for orbiting scroll side. Dynamic analysis on the fixed and orbiting scroll members and the shafts of the scroll expander showed that using of these devices for complying thermal expansion caused large variations of the forces acting on the fixed scroll keys and on the power transmitting shafts and also on the shaft bearings.