• The Journal of the Korea Contents Association
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• v.5 no.2
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• pp.95-105
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• 2005

As a research on PKI is being very popular, the study relating to certificate status validation is being grown with aim to reduce an overhead of the protocol and to provide an efficient operation. The OCSP of the standard protocol related to the study enables applications to determine the revocation state of an identified certificate. However, the OCSP server can not service millions of certificate status validation requests from clients in a second on E-commerce because of the computational time for signature and verification. So, we propose the Real-time Certificate Status Validation Protocol(RCSVP) that has smaller computational time than OCSP. RCSVP server reduce the computational time of certificate status validation using hash function and common secret value. Also RCSVP client does not need the computational time of certificate verification to acquire the public key from an identified certificate. Therefore, the proposed protocol enables server to response millions of certificate status validation requests from clients in a second on E-commerce.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.3B
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• pp.91-99
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• 2008

In this paper, we design the function of ULSLE(Upper Layer Shared LAN Emulation) to provide both the efficient LAN service and compatibility with 802.1D bridge in Hybrid two-stage AWG based WDM-PON. The ULSLE layer lies above MAC control layer in order to provide a mean to interface WDM-PON and 802.1D bridge. It also performs LAN emulation based on PON-Tag which is only used to decide both the transmission mode and the destination of frames transmitted from ONUs. That is, the PON-Tag is not used for downstream frames but destination address field in original frame instead. This decreases the processing overhead and complexity caused by PON-Tag at OLT and ONU. The verification of designed ULSLE is performed according to the specific scenarios based on transmission mode and destination using OPNET.

• Journal of KIISE:Computer Systems and Theory
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• v.32 no.3
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• pp.115-124
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• 2005

When the application code is downloaded into the mobile device, it is important to provide authentication. Usually, mobile code execution is overlapped with downloading to reduce transfer delay. To the best of our knowledge, there has not been any algorithm to authenticate the mobile code in this environment. In this paper, we present two efficient code authentication schemes that permit overlapping of execution and downloading under the two cases: the first is when the order of transmission of code chunks is determined before the transmission and the second is when this order is determined during the transmission. The proposed methods are based on hash chaining and authentication trees, respectively. Especially, the latter scheme utilizes previously received authentication informations to verify the currently received chunk, which reduces both communication overhead and verification delay. When the application code consists of n chunks, communication overheads of the both schemes are 0(n) and verification delays of these two schemes are O(1) and O(log n), respectively.

• Journal of the Korean Society for Nondestructive Testing
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• v.32 no.6
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• pp.637-647
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• 2012

Bridges are ones of fundamental facilities for roads which become social overhead capital facilities and they are designed to get safety in their life cycles. However as time passes, bridge can be damaged by changes of external force and traffic environments. Therefore, a bridge should be repaired and maintained for extending its life cycle. The working load on a bridge is one of the most important factors for safety, it should be calculated accurately. The most important load among working loads is live load by a vehicle. Thus, the travel characteristics and weight of vehicle can be useful for bridge maintenance if they were estimated with high reliability. In this study, a B-WIM system in which the bridge is used for a scale have been developed for measuring the vehicle loads without the vehicle stop. The vehicle loads can be estimated by the developed B-WIM system with the reaction responses from the supporting points. The algorithm of developed B-WIM system have been verified by numerical analysis.

• Proceedings of the IEEK Conference
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• 2008.06a
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• pp.89-90
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• 2008

We present an implementation and it's real-sea test of an underwater acoustic communication system, which allows the system to reduce complexity and increase robustness in time variant underwater environments. For easy adaptation to complicated and time-varying environments of the ocean, all-digital transmitter and receiver systems were implemented. For frame synchronization the CAZAC sequence was used, and QPSK modulation/demodulation method with carrier frequency of 25kHz and a bandwidth of 5kHz were applied to generate 10kbps transmission rate including overhead. To improve transmission quality, we used several techniques and algorithms such as adaptive beamforming, adaptive equalizer, and convolution coding/Viterbi decoding. For the verification of the system performance, measurement of BER has been done in a very shallow water with depth of 20m at JangMok, Geoje. During the experiment, image data were successfully transmitted up to about 9.6km.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.3
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• pp.1212-1228
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• 2016

Secure communication is an important aspect of today's interconnected environments and it can be achieved by the use of cryptographic algorithms and protocols. However, many existing cryptographic mechanisms are tightly integrated into communication protocols. Issues emerge when security vulnerabilities are discovered in cryptographic mechanisms because their replacement would eventually require replacing deployed protocols. The concept of cryptographic agility is the solution to these issues because it allows dynamic switching of cryptographic algorithms and keys prior to and during the communication. Most of today's secure protocols implement cryptographic agility (IPsec, SSL/TLS, SSH), but cryptographic agility mechanisms cannot be used in a standalone manner. In order to deal with the aforementioned limitations, we propose a lightweight cryptographically agile agreement model, which is formally verified. We also present a solution in the Agile Cryptographic Agreement Protocol (ACAP) that can be adapted on various network layers, architectures and devices. The proposed solution is able to provide existing and new communication protocols with secure communication prerequisites in a straightforward way without adding substantial communication overhead. Furthermore, it can be used between previously unknown parties in an opportunistic environment. The proposed model is formally verified, followed by a comprehensive discussion about security considerations. A prototype implementation of the proposed model is demonstrated and evaluated.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.12
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• pp.4661-4676
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• 2014

In Wireless Mesh Networks (WMN), an authentication technique can be compromised due to the distributed network architecture, the broadcast nature of the wireless medium and dynamic network topology. Several vulnerabilities exist in different protocols for WMNs. Hence, in this paper, we propose trust based authentication and key establishment for secure routing in WMN. Initially, a trust model is designed based on Ant Colony Optimization (ACO) to exchange the trust information among the nodes. The routing table is utilized to select the destination nodes, for which the link information is updated and the route verification is performed. Based on the trust model, mutual authentication is applied. When a node moves from one operator to another for accessing the router, inter-authentication will be performed. When a node moves within the operator for accessing the router, then intra-authentication will be performed. During authentication, keys are established using identity based cryptography technique. By simulation results, we show that the proposed technique enhances the packet delivery ratio and resilience with reduced drop and overhead.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.8
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• pp.1256-1261
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• 2015

Along with the increase of railway catenary system operation speed to 400 km/h, there have been growing demands for good quality current collection systems that satisfy quality standards as well as criteria for safe working. Retaining uniform elasticity tension of contact wires is essential in maintaining high quality contact between pantograph and OCL (Overhead Contact Line) of current collection systems in high speed railways. Therefore, the tension of contact wire must be kept within tight tolerance limits in both working conditions and adverse weather conditions of catenary system. In accordance with these conditions, this paper presents a real time monitoring system for the tensioning device of the newly installed catenary system on the special route of Honam high speed line for 400 km/h operation. For the verification of the true value of tension of contact wires, we have developed ring-type tensioning sensors which were installed on supporting points of mast which compose the catenary system. According to the field test performed on the Honam high speed line catenary system, variation of tension was measured accurately in real-time.

• Journal of KIISE:Computer Systems and Theory
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• v.31 no.11
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• pp.617-625
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• 2004

We propose an efficient stream authentication scheme that is an improvement of PCC scheme by using information dispersal algorithm. The drawback of PCC scheme is that received packets for each group are verifiable only if the signature packet of the group is successfully received. The proposed scheme processes the signature packet by introducing some amount of redundancy and splitting the result into pieces, which are then transmitted. The receiver is able to reconstruct the signature packet if the number of the received pieces is larger than the threshold. It is shown that under the same communication overhead verification probability of the proposed scheme is higher than that of SAIDA. Moreover, its computational cost is lower than that of SAIDA.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.12C
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• pp.1722-1728
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• 2004

To discover a certificate path is a very important topic in the PKI with a lot of candidate paths. The certificate path discovery processing is executed via many verifications and as the number of verification times increases, the validity of the discovered path becomes high. The selection of the path with high validity provides high-speed certificate validation by reducing the number of repetition times of path discovery and validation processing. Otherwise, there is a problem that the speed and computation overheads are increased. In this paper, we propose an efficient certificate path discovery algorithm can make high the certificate validity with low overhead.