• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.367-372
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• 2001

Feature restoration is that restore feature to 3D solid model using the feature information in STEP AP224. Feature is very important in CAPP, but feature information is defined very complicated in STEP AP224. This paper recommends the algorithm of extraction the feature information in physical STEP AP224file. This program import STEP AP224 file, parse the geometric and topological information, the tolerance data, and feature information line-by-line. After importation and parsing, store data into database. Feature restoration module analyze database including feature information, extract feature information, e.g. feature type, feature's parameter, etc., analyze the relationship and then restore feature to 3D solid model.

• JSTS:Journal of Semiconductor Technology and Science
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• v.9 no.3
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• pp.148-152
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• 2009

Recent CMOS technology scaling has seriously eroded the bit-line noise immunity of register files due to the consequent increase in active bit-line leakage currents. To restore its noise immunity while maintaining performance, we propose and evaluate a $256{\times}40$-bit register file incorporating dual-$V_t$ bit-lines with a boosted gate overdrive voltage in 65 nm bulk CMOS technology. Simulation results show that the proposed bootsrapping scheme lowers leakage current by a factor of 450 without its performance penalty.

• Journal of Internet Computing and Services
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• v.21 no.3
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• pp.93-102
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• 2020

In order for data obtained through all stages of digital crime investigation to be recognized as evidence capability, it must satisfy legal / technical requirements. In this paper, we propose a mechanism and implement software to provide digital forensic evidence by automatically recovering files by scanning / inspecting the unallocated area inside the storage disk block without relying on information provided by the file system. The proposed technique checks / analyzes the RAW disk data of the system under analysis in 512-byte block units based on information on the storage format / file structure of various files stored on the disk without referring to the file system-related information provided by the operating system. The file carving process was implemented, and a smart carving mechanism was proposed to intelligently restore deleted or damaged files in the storage device. As a result, we have provided a block based smart carving method to intelligently identify fragmented and damaged files in storage efficiently for forgery analysis on digital forensic investigation.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.27 no.5
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• pp.1107-1115
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• 2017

The most commonly used PKZIP format is a ZIP file, as well as a file format used in MS Office files and application files for Android smartphones. PKZIP format files, which are widely used in various areas, require structural analysis from the viewpoint of digital forensics and should be able to recover when files are damaged. However, previous studies have focused only on recovering data or extracting meaningful data using the Deflate compression algorithm used in ZIP files. Although most of the data resides in compressed data in the ZIP file, there is also forensically meaningful data in the rest of the ZIP file, so you need to restore it to a normal ZIP file format. Therefore, this paper presents a technique to recover a damaged ZIP file to a normal ZIP file when given.

• KIPS Transactions on Computer and Communication Systems
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• v.6 no.1
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• pp.31-42
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• 2017

Thumbnail, the small sized graphic file such as JPEG or GIF, serves to help the users to be recognized as a rapidly helps to make it easier recognize while browsing the large sized graphic file. Gallery application, which is installed in a later version of the 4.4.x(Kitkat) Android smartphone records the generated time of graphic file in thumbnail metadata. Thumbnail can be used to draw up the timeline of user action about user's action such as creation, modification, deletion with original graphic file analysis. Also, take advantage of the features thumbnails are stored sequentially in a single thumbcache file, even if the thumbcache is deleted, we can restore the thumbnails. This paper illustrates the feature of thumbnail created by Android OS basic gallery app and methods for utilization in digital forensics.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.27 no.6
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• pp.1373-1383
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• 2017

Deduplication is a function to effectively manage data and improve the efficiency of storage space. When the deduplication is applied to the system, it makes it possible to efficiently use the storage space by dividing the stored file into chunks and storing only unique chunk. However, the commercial digital forensic tool do not support the file system analysis, and the original file extracted by the tool can not be executed or opened. Therefore, in this paper, we analyze the process of generating chunks of data for a Windows Server 2012 system that can apply deduplication, and the structure of the resulting file(Chunk Storage). We also analyzed the case where chunks that are not covered in the previous study are compressed. Based on these results, we propose the method to collect deduplicated data and reconstruct the original file for digital forensic investigation.

• Proceedings of the IEEK Conference
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• 2003.11b
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• pp.231-234
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• 2003

This paper designs and implements fault-tolerant server of meta server for shared filesystem (SANfs) in SAN environment. SANfs is the filesystem that many clients can share data in Network-attached storage in SAN environment and meta server is the server that processes file operation in SANfs. The focus of this paper is the implementation of fault-tolerant server of meta server in SANfs. In the event of a meta server, meta server failovers to a fault-tolerant server where its processing continues seamlessly. If meta server doesn't restore, fault-tolerant server searches reliable client and makes another fault-tolerant server and work as meta server. Heartbeat monitors meta server and shadow server and controls them.

• Proceedings of the Korean Society of Computer Information Conference
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• 2011.06a
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• pp.197-201
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• 2011

검찰과 경찰에서는 압수수색을 통해 조사를 수행하는데, 기업들은 압수수색 수사를 받기 전에 회계 DB 및 회계 관련 파일 삭제, 파손 및 은닉하는 등의 문제점을 발생시키고 있다. 2008년 삼성화재 비자금 조성 사건과, 2009년 교하 복합커뮤니티 센터의 입찰비리 사건 등 기업회계장부의 포렌식 기술적용방법 문제 등이 발생하고 있다. 본 논문에서는 포렌식 수사 도구인 EnCase, FinalData 등을 연구하고, 기업의 회계 서버에 대해 압수수색 준비와 압수 수색, 획득 증거 분석 등의 절차를 연구한다. 기업의 회계 서버 압수수색 후에 디스크에서 포렌식 증거분석에서 실시되는 증거물 원본 파일보관, 원본성이 입증된 사본생성, 삭제 파일 검사 및 복원, 삭제 내용 확인, 원본 파일과의 대조를 실험을 한다. 본 연구 결과는 포렌식 기술발전에 기여하게 될 것이다.

• The Journal of the Korea Contents Association
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• v.20 no.8
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• pp.368-374
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• 2020

Journaling file systems (JFS) manage changes of file systems not yet committed in a data structure known as a journal to restore the file system in the event of an unexpected failure. Extra write operations required for journaling negatively affect the performance of JFS. The high-performance and byte-addressable non-volatile memory (NVM) was expected to easily mitigate these performance problems by providing NVM space as journal storage. However, even with such non-volatile memory technologies, performance problems still arise due to scalability problems inherent in processing transactions of JFS. To solve this problem, we proposes a technique for processing file system transactions for scalable performance. To this end, lock-free data structures are used and multiple I/O requests are allowed to simultaneously be processed on high-performance storage devices with multiple I/O channels. We evaluate the file system with the proposed technique by comparing the original ext4 file system and the recent proposed NVM-based journaling file system on a multi-core server, and experimental results show that our file system has better performance (up-to 2.9/2.3 times) than the original ext4 file system and the recent NVM-based journaling file system, respectively.

• The Journal of the Acoustical Society of Korea
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• v.36 no.2
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• pp.136-143
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• 2017

In this paper, we propose a method for restoring damaged audio files using deep neural network. It is different from the conventional file carving based restoration. The purpose of our method is to infer lost information which can not be restored by existing techniques such as the file carving. We have devised methods that can automate the tasks which are essential for the restoring but are inappropriate for humans. As a result of this study it has been shown that it is possible to restore the damaged files, which the conventional file carving method could not, by using tasks such as speech or nonspeech decision and speech encoder recognizer using a deep neural network.