• Journal of the Korea Institute of Information Security & Cryptology
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• 제22권1호
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• pp.57-65
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• 2012

People leave voicemails or record phone conversations in their daily cell phone use. Sometimes important voice data is deleted by the user accidently, or purposely to cover up criminal activity. In these cases, deleted voice data must be able to be recovered for forensics, since the voice data can be used as evidence in a criminal case. Because cell phones store data that is easily fragmented in flash memory, voice data recovery is very difficult. However, if there are identifiable patterns for the deleted voice data, we can recover a significant amount of it by researching images of it. There are several types of voice data, such as QCP, AMR, MP4, etc.. This study researches the data recovery solutions for EVRC codec and AMR codec in QCP file, Qualcumm's voice data format in cell phone.

• KIPS Transactions on Computer and Communication Systems
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• 제12권7호
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• pp.209-216
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• 2023

Modern HPC systems are equipped with many-core CPUs with dozens of cores. When performing parallel I/O in such a system, there is a limit to scalability due to the problem of the LRU lock management policy of the Linux system. The study proposes an improved FinerLRU to solve this problem. Our new FinerLRU improves the parallel write performance of file systems using the buffer cache through granular lock management by increasing the number of LRU locks upto the maximum number of cores. The proposed method was implemented in Linux 5.18.11, and the performance was measured on two types of CPUs, Intel Icelake Xeon and Intel Knights landing, with different characteristics, and it was found that a performance improvement of about two times can be obtained in both types of systems.

• Journal of Internet Computing and Services
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• 제13권3호
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• pp.49-59
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• 2012

Throughout developing digital technology, reproduction of image is growing better day by day. And at the same time, diverse image editing softwares are developed to manage images easily. In the process of editing images, those programs could delete or modify EXIF files which have the original image information; therefore images without the origin source are widely spread on the web site after editing. This matter could affect analysis of images due to the distortion of originality. Especially in the court of law, the source of evidence should be expressed clearly; therefore digital image EXIF file without deletion or distortion could not be the objective evidence. In this research, we try to trace the identification of a digital camera in order to solve digital images originality, and also we focus on lens distortion correction algorism which is used in digital image processing. Lens distortion correction uses mapping algorism, and at this moment it also uses interpolation algorism to prevent aliasing artifact and reconstruction artifact. At this point interpolation shows the similar mapping pattern; therefore we want to find out the interpolation evidence. We propose a minimum filter algorism in order to detect interpolation pattern and adjust the same minimum filter coefficient in two areas; one has interpolation and the second has no interpolation. Throughout DFT, we confirm frequency character between each area. Based on this result, we make the final detection map by using differences between two areas. In other words, thereby the area which has the interpolation caused by mapping is adjusted using minimum filter for detection algorism; the second area which has no interpolation tends to different frequency character.

• Journal of the Korea Institute of Information Security & Cryptology
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• 제28권2호
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• pp.347-355
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• 2018

Ransomware uses symmetric-key algorithm such as a block cipher to encrypt users' files illegally. If we find the traces of a block cipher algorithm in a certain program in advance, the ransomware will be detected in increased rate. The inclusion of a block cipher can consider the encryption function will be enabled potentially. This paper proposes a way to determine whether a particular program contains a block cipher. We have studied the implementation characteristics of various block ciphers, as well as the AES used by ransomware. Based on those characteristics, we are able to find what kind of block ciphers have been contained in a particular program. The methods proposed in this paper will be able to detect ransomware with high probability by complementing the previous detection methods.

• Journal of the Korea Institute of Information and Communication Engineering
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• 제20권12호
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• pp.2410-2416
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• 2016

Recently, most countries in the world have pursued a denuclearization. So it has been of interest to increase to Nuclear weapon in such as North Korea's continued nuclear test. Pulsed gamma rays produced in the nuclear explosion and the space environment can give the big damage to the electronic device in a very short period of time. To confirm the extent of damage of these electronic devices, pulsed gamma irradiation facility that can occur in nuclear weapon or space environment are required. In this paper, we implemented the pulsed gamma-ray detection module and analyzed output of the irradiation test. We have experimented using an electron beam accelerator research facilities in Pohang Accelerator similar conditions to equip and Nuclear weapon. As a result, we confirmed that the pulsed gamma rays emitted by the gamma radiation and electron beam conversion device. The results of this paper will contribute to improve the reliability and accuracy of studies for utilizing pulsed gamma rays.

• Proceedings of the Korean Information Science Society Conference
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• 한국정보과학회 2005년도 한국컴퓨터종합학술대회 논문집 Vol.32 No.1 (A)
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• pp.826-828
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• 2005

이동 기기의 저장 장치로 플래시 메모리가 널리 사용되고 있으며 고정 하드 디스크를 대체하는 저장 매제로 부상하고 있다. 그러므로 플래시 메모리의 특성을 잘 이해하고, 최대한 효율적으로 플래시 메모리를 사용할 필요성이 있다. 이러한 역할을 해주는 것은 플래시 내부의 시스템 소프트웨어인 FTL(Fiash Translation Layer)이다. FTL은 운영체제가 디스크에 전달하는 블록을 물리적인 플래시 메모리에 맵핑하는 역할을 한다. 그러므로 플래시 메모리의 성능은 FTL 알고리즘이 결정한다. 플래시를 대체한 플래시 디스크에서는 기존의 파일 시스템이 탑재되며 간단한 섹터 기반외 이동형 기기에서와는 다른 특성을 가진다. FTL 성능을 평가하기 위해서는 실제적으로 플래시 메모리가 장착된 제품들이 동작하는 시스템에서 실험을 해야 한다. 많은 플래시 디스크는 윈도우즈에서 동작하므로 윈도우즈의 디스크 I/O를 추출하여 실험을 해야만 한다. 본 논문에서는 윈도우즈에서 물리적인 디스크 I/O 패턴을 추출하여 FTL 알고리즘의 성능을 평가하기 위한 도구 개발에 대하여 설명하고 이에 대한 간단한 결과를 보인다.

• Journal of the Korea Institute of Information and Communication Engineering
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• 제23권10호
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• pp.1269-1274
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• 2019

The paper presents a design of simple four-element microstrip-patch array antenna that is suitable for 5G applications. The proposed array consists of four rectangular microstrip patch elements with semicircular etches made on both sides of each elements. The antenna is fed using the combination of series and corporate feeding networks. The size of the ground is also changed to improve the antenna frequency. Finally, yagi elements are also added to improve the directive gain of the antenna. The presented microstrip patch array is able to achieve wide frequency bandwidth of 21.95-31.86 GHz. The antenna has also attained gain of 9.7 dB at 28 GHz and has maintained high gain and high directivity throughout the frequency band. The proposed array antenna fed by series-corporate feeding network, with low profile and simple structure is a good candidate for 5G applications.

• Journal of the Korea Institute of Information Security & Cryptology
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• 제33권5호
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• pp.753-760
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• 2023

KakaoTalk has the highest market share among domestic messengers. As such, KakaoTalk's conversation content is an important evidence in digital forensics, and the conversation is stored in the form of an encrypted database on a user's device. In addition, macOS has the characteristic that it is difficult to access because the disk encryption function is basically activated. The decryption method of the KakaoTalk database for Windows has been studied, but the decryption method has not been studied for KakaoTalk for macOS. In this paper, research the decryption method of the KakaoTalk database for macOS and a way to Brute-Force plan using the characteristics of KakaoTalk's UserID and compare it with KakaoTalk for Windows to examine the commonalities and differences. The results of this paper are expected to be used to analyze users' actions and events when investigating crimes using macOS.

• Spatial Information Research
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• 제23권1호
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• pp.41-48
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• 2015

BIM Technology contains data from the life cycle of facility through 3D modeling. For these, one building products the huge file because of massive data. One of them is IFC which is the standard format, and there are issues that large scale data processing based on geometry and property information of object. It increases the rendering speed and constitutes the graphic card, so large scale data is inefficient for screen visualization to user. The light weighting of large scale BIM data has to solve for process and quality of program essentially. This paper has been searched and confirmed about light weight techniques from domestic and abroad researches. To control and visualize the large scale BIM data effectively, we proposed and verified the technique which is able to optimize the BIM character. For operating the large scale data of facility on web based GIS platform, the quality of screen switch from user phase and the effective memory operation were secured.

• Journal of KIISE
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• 제41권11호
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• pp.982-991
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• 2014

The integrity assurance of recorded video by car black boxes are necessary as the car black box is becoming more popular. In this paper, we propose a video data integrity assurance scheme reflecting the features of car black box. The proposed method can detect any kind of deletion, insertion, modification of frames by cyclic chaining using inter block relation. And, it provides the integrity assurance function consistently even in cases of file overwriting because of no more free space in storage, partial file data lost. And non-repudiation is supported. Experimental results with a car black box embedded system with A8 application processor show that our method has a feasible computational overhead to process full HD resolution video at 30 frames per second in a real time.