• Proceedings of the Korean Institute of Communication Sciences Conference
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• 2004.11a
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• pp.156-156
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• 2004

• Proceedings of the KIEE Conference
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• 1996.07b
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• pp.1243-1247
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• 1996

In this paper, a small PLC system is designed and developed for the distributed building control and fire control system. It uses 8031, a 8-bit micro controller from Intel Inc. The size of the PLC is $7cm{\times}8cm$ and the PLC can accept 4 sensor inputs and drive 4 relay outputs, which operates at 24V. Multiple access of PLC by one host computer is implemented by assigning a unique 10 to each PLC, which ranges from 0 to 126. The operation starts by sending a command packet from host computer to a PLC and the PLC of the same 10 fetches the command packet by comparing the first byte of the command packet with its own 10. The PLC is programmed to perform a various functions and the function is selected by the content of the command byte, which is the second byte of the command packet. The third byte, which is the last byte, is a checksum byte. The checksum byte is the sum of the first byte and the second byte and is used to detect the communication error. Depending on the content of the command byte, PLC performs the desired function and returns the response packet back to the host computer. The response packet is also a three-byte packet, 10 byte, response byte and checksum byte. For the independent operation of PLC without being controlled by the host computer, variable length RULE data packet is sent to PLC. In case the communication line is broken, the PLC perform the independent operation by referencing the RULE data. The applicable areas are; building automation system, distributed factory automation, measurement of temperature of toxic or dangerous area.

• Journal of KIISE:Computing Practices and Letters
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• v.14 no.2
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• pp.206-210
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• 2008

The most noticeable aspect of progressive streaming is the media playback during its download through TCP to avoid a lengthy wait for a content to finish downloading. By employing TCP, it is usually possible to detect lost packets by using the checksum and sequence numbering functions of TCP Thereafter, we can recover the lost packets by the retransmission function of TCP. However, there must remain enough amount of media data in the recipient buffer in order to guarantee seamless media playback even during retransmission. In this paper, we propose an efficient algorithm for determining the initial buffering time before start of playback to guarantee seamless playback during retransmission considering the probability of client buffer under-flow. The effectiveness of the proposed algorithm will be proved through extensive simulation results.

• Journal of Korean Society for Geospatial Information Science
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• v.6 no.1 s.11
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• pp.27-34
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• 1998

A Unique Feature Identifier(UFID) is a way of referring to a feature, generally representing a tangible feature in the real world. In other words, a UFID uniquely identifies the related feature in the database and is normally used to link two or more databases together. This paper presents a UFID system aiming at the internal uses for National Geography Institute(NGI) as well as external uses for National Geographic Information System(NGIS) generally to link datasets together. The advantage of the proposed type of UFID lies in the meaningful nature of the identifier in providing a direct spatial index - administrative area and feature code. The checksum character proposed in this research is designed to remove any uncertainty about the number being corrupt. It will account lot digit transposition during manual input as well as corruption in transfer or processing.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.7 no.1
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• pp.75-83
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• 2008

In this paper, we propose an efficient algorithm that assigns single temporary IPv4 address and port number to improve efficiency of IPv4 address that is allocated in DSTM service. And, we have analyzed the elementary functions for DSTM and have designed the functional modules. Also, we have implemented the DTI interface for encapsulation and decapsulation of IPv6 packets. The performance analysis and comparison are investigated whether the appropriate interworking service is possible or not. Our observation results show that the performance of IPv4 over IPv6 tunneling is suitable to DSTM service due to the reduction of delay by eliminating checksum calculations in the header of IPv6 tunneling.

• The Transactions of the Korea Information Processing Society
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• v.1 no.3
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• pp.391-397
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• 1994

In this paper, we have developed a PLD Designer which is a design tool for digital circuits design using PLD device. PLD designer consists of a state graphic editor to extract boolean equations from state table within 20 states of FSM and a pin map editor to assign pin map for PLD device(PAL16R4, PAL22V10, GAL16V8, etc), which is suitable for extracted boolean equations. Also pin map editor generates a necessary JEDEC file to implement PLD device by using fuse map and checksum algorithm. To verify extracted boolean equation, we have developed simulation test vector generation algorithm. The results of JEDEC files generated by PLD designer is same with the results of JEDEC files generated by PALASM.

• Proceedings of the Korean Information Science Society Conference
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• 2005.11a
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• pp.151-153
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• 2005

체크섬은 에러검출의 우수성 때문에 TCP등에서 널리 사용하고 있다. 이 체크섬 방식은 연산이 간단하고 빠르나, 미검출 에러가 생기는 경우가 있기 때문에 여러 다른 형태의 체크섬 방식등이 연구가 진행되고 있고 각 방식에 성능과 효율면에서 상관관계가 있어 어플리케이션에따라 선택에 어려움이 있는 경우가 있다. 이에 저자는 새로운 개념인 이차원 체크섬이라는 방식을 제안하고자 한다. 알고리즘이 단순하면서도 기존의 체크섬의 미검출 에러의 문제를 현저하게 줄일 수 있고 비용-이득 스펙트럼상에서 매우 효과적이고 효율적이다.

• Honam Mathematical Journal
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• v.33 no.2
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• pp.153-161
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• 2011

Greg([Greg]) considered that $$N_k= \sum\limits_{i=1}^k(-1)^{i+1}P_{i,k}(p)N_1^i$$ where the $P_{i,k}$'s were polynomials with positive integer coefficients. In this paper, we will give the equations for $\sum\limits{P_{i,k}$ modulo 3. Using this, if we send a information for elliptic curve to sender, we can make a new checksum method for Manchester coding in IEEE 802.3 or IEEE 802.4.

• Proceedings of the IEEK Conference
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• 2003.11b
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• pp.53-56
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• 2003

Ethernet is one of the most successful LAN technologies. Now gigabit ethernet is available in real network and some network interface cards(NIC) supports TCP segment offloading (TSO), IP checksum offloading(ICO), Jumbo frame and interrupt moderation. If we use this features appropriately, we obtain high throughput with low CPU utilization. This paper represents the network performance by varying above features.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.29 no.1
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• pp.205-214
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• 2019

Android uses app cache files to improve app execution performance. However, this optimization technique may raise security issues that need to be examined. In this paper, we present a practical design of "Android app cache manipulation attack" to intentionally modify the cache files of a target app, which can be misused for stealing personal information and performing malicious activities on target apps. Even though the Android framework uses a checksum-based integrity check to protect app cache files, we found that attackers can effectively bypass such checks via the modification of checksum of the target cache files. To demonstrate the feasibility of our attack design, we implemented an attack tool, and performed experiments with real-world Android apps. The experiment results show that 25 apps (86.2%) out of 29 are vulnerable to our attacks. To mitigate app cache manipulation attacks, we suggest two possible defense mechanisms: (1) checking the integrity of app cache files; and (2) applying anti-decompilation techniques.