• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.4A
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• pp.512-518
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• 2000

Self-certified public keys, introduced by Girault allow the authenticity of public keys to be verified implicitly during the use of the keys. This paper first presents new concept of verifiable self-certified public keys and provides concrete examples satisfying our conditions. Verifiable self-certified public keys combine the benefit of certification-based schemes and Girault's self-certified public keys. Furthermore, we also cryptanalyze Petersen's pseudonymous self-certified keys and present the more secure protocol.

• Proceedings of the KIEE Conference
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• 1998.07b
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• pp.672-674
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• 1998

Inside keys for the automobiles are the keys whose key teeth are engraved on the inside of the keys. These types of the keys are very effective in prohibiting making the copies of the keys for the criminal purposes and have excellent mechanical strenth comparing with the ordinary types of the keys. In this paper, a development of the control system for the milling machine which is used for cutting the teeth of the inside keys. This machine is controlled by a computer and the cutting is done automatically according to the key codes which are contained in the key code file. This work is presented to show an example of the industry-university cooperation.

• Journal of Computing Science and Engineering
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• v.6 no.3
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• pp.193-206
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• 2012

Keys play a fundamental role in all data models. They allow database systems to uniquely identify data items, and therefore, promote efficient data processing in many applications. Due to this, support is required to discover keys. These include keys that are semantically meaningful for the application domain, or are satisfied by a given database. We study the discovery of keys from SQL tables. We investigate the structural and computational properties of Armstrong tables for sets of SQL keys. Inspections of Armstrong tables enable data engineers to consolidate their understanding of semantically meaningful keys, and to communicate this understanding to other stake-holders. The stake-holders may want to make changes to the tables or provide entirely different tables to communicate their views to the data engineers. For such a purpose, we propose data mining algorithms that discover keys from a given SQL table. We combine the key mining algorithms with Armstrong table computations to generate informative Armstrong tables, that is, key-preserving semantic samples of existing SQL tables. Finally, we define formal measures to assess the distance between sets of SQL keys. The measures can be applied to validate the usefulness of Armstrong tables, and to automate the marking and feedback of non-multiple choice questions in database courses.

• Smart Structures and Systems
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• v.24 no.3
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• pp.345-360
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• 2019

The shear keys are set in a seismic isolation system to resist the long-term service loadings, and are cut off to isolate the earthquakes. This paper investigated the influence of shear keys on the seismic performance of a vertical spring-viscous damper-concave Coulomb friction isolation system by an incremental dynamic analysis (IDA) and a performance-based assessment. Results show that the cutting off process of shear keys should be simulated in a numerical analysis to accurately predict the seismic responses of isolation system. Ignoring the cutting off process of shear keys usually leads to untrue seismic responses in a numerical analysis, and many of them are unsafe for the design of isolated structure. And those errors will be increased by increasing the cutting off force of shear keys and decreasing the spring constant of shear keys, especially under a feeble earthquake. The viscous damping action postpones the cutting off time of shear keys during earthquakes, and reduces the seismic isolation efficiency. However, this point can be improved by increasing the spring constant of shear keys.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1998.10a
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• pp.120-127
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• 1998

This paper deals with the dynamic responses of the multi-span continuous bridge with longitudinal shear keys. It is motivated by a need to understand the effects of longitudinal shear keys which may be used for the reduction of the longitudinal seismic force in continuous bridges. The results show that (1) The force reduction of fixed pier is proportional to the ratio of gap size and elastic maximum displacement of the bridges without shear keys ; (2) The thermal movement has little effect on the response of the continuous bridges with shear keys. Also the simplified equation is proposed to calculate the maximum response of the continuous bridges with longitudinal shear keys. The equation requires only the elastic analysis results of the bridge and the gap size between superstructure and shear keys.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1999.10a
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• pp.313-318
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• 1999

The seismic performance of multi-span bridge without seismic detailing is found to be insufficient in longitudinal direction. Shear keys and stoppers can be introduced as an alternative to enhance seismic capacity. The capacity curve of bridge with shear keys is obtained considering two extreme contact conditions of shear keys. Its curve is converted into ADRS spectra and compared with demand spectra. It is concluded that seismic performance can be improved effectively by shear keys and its performance can be evaluated graphically on the ADRS specta.

• Archives of design research
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• v.15 no.3
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• pp.241-248
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• 2002

Researches of Hangul automation have been focused mainly on the set of character system. But, practical problem of using the Korean standard keyboard system of two sets is increment of errors and fatigue due to frequent use of shift keys. The author formulate a hypothesis as follows to solve the problem. 'Changing location and design of shift keys can reduce errors in typing Korean by avoiding interferences with other keys when pressing shift keys.' This study verify the hypothesis by the analysis of experiments using improved keyboard prototypes which have changed layout and design of shift keys. On the result, change of shift key location causes confusion to experienced user. But, while keeping its location, removing other keys at the bottom row and magnifying size of shift keys decrease errors in typing by avoiding interferences. And, the efficiency of typing in Korean is increased, too, because there is not any influence on typing speed. This study focuses on layout and design of shift keys only, but further study for entire layout of keyboard including alternative location of other function keys is needed to improve general usability.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.13 no.4
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• pp.71-84
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• 2003

Self-certified public keys need not be accompanied with a separate certificate to be authenticated by other users because the public keys are computed by both the authority and the user. At this point, verifiable self-certified public keys are proposed that can determine which is wrong signatures or public keys if public keys are used in signature scheme and then verification of signatures does not succeed. To verify these public keys, key generation center's public key trusted by users is required. If all users trust same key generation center, public keys can be verified simply. But among users in different domains, rusty relationship between two key generation centers must be accomplished. In this paper we propose inter-domain verifiable self-certified public keys that can be verified without certificate between users under key generation centers whose trusty relationship is accomplished. Also we present the execution of signature and key distribution between users under key generation centers use different public key parameters.

• Journal of Korean Association for Spatial Structures
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• v.7 no.1 s.23
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• pp.45-53
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• 2007

Recently, high-rise base isolated building structures with shear keys are often constructed in Japan which frequently occurs earthquakes. High-rise buildings are less damaged because those buildings have longer natural period than md or low rise buildings. The shear key is device that prevents the base isolators operating by the wind loads not by the earthquake loads. In case of big base shear force acts on the shear keys by earthquake, this device is broken and base isolator is operated. Therefore, seismic intensities play a role in acting on the shear keys. If wind loads are hither than the earthquake loads, the shear keys designed by wind loads are not operated in earthquakes. So, the requirements of shear keys in high-rise base isolated building structures must be examined in Korea with moderate seismic legions. In this study shear keys are applied with 5 and 15 stories base isolated building structures and investigated their dynamic responses to original and 1/2 scale downed El Centre NS(1940) ground motions. The results show that the yield shear forces of the shear keys affect significantly the dynamic behavior of base isolated building structures

• Journal of KIISE:Information Networking
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• v.30 no.6
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• pp.705-713
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• 2003

For group security to protect group data or to charge, group keys should be updated via key update messages when the membership of group changes. If we lose these messages, it is not possible to decrypt the group data and so this is why the recovery of lost keys is very significant. Any message lost during a certain member is logged off can not be recovered in real-time. Saving all messages and resending them by KDC (Key Distribution Center) not only requests large saving spaces, but also causes to transmit and decrypt unnecessary keys. This paper analyzes the problem of the loss of key update messages along with other problems that may arise during member login procedure, and also gives an efficient method for recovering group keys and auxiliary keys. This method provides that group keys and auxiliary keys can be recovered and sent effectively using information stored in key-tree. The group key generation method presented in this paper is simple and enable us to recover any group key without storing. It also eliminates the transmissions and decryptions of useless auxiliary keys.