• KIPS Transactions on Computer and Communication Systems
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• v.6 no.1
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• pp.25-30
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• 2017

The influence of the data deletion method which is one of anti-forensic techniques is substantial in terms of forensic analysis compared to its simplicity of the act. In academic world, recovery techniques on deleted files have been continuously studied in response to the data deletion method and representatively, the file system-based file recovery technique and file format based recovery technique exist. If there's metadata of deleted file in file system, the file can be easily recovered by using it, but if there's no metadata, the file is recovered by using the signature-based carving technique or the file format based recovery technique has to be applied. At this time, in the file format based recovery technique, the file structure analysis and possible recovery technique should be provided. This paper proposes the page recovery technique on deleted PDF file based on the structural characteristics of PDF file. This technique uses the tag value of page object which constitutes one page of PDF file. Object is extracted by utilizing each tag value as a kind of signature and by analyzing extracted object, the metadata of PDF file is recombined and then it's reconfigured page by page. Recovering by page means that even if deleted PDF file is damaged, even some pages consisting of PDF file can be recovered. Generally, if the file system based file is not recoverable, deleted file is recovered by applying the signature based carving technique. The technique which we proposed in this paper can recover PDF files that are damaged. In the digital forensic perspective, it can be utilized to recover more data than previously.

• Journal of Korea Society of Digital Industry and Information Management
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• v.11 no.4
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• pp.69-79
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• 2015

This research proposes a modified data hiding method to hide data in a slack space of an NTFS index record. The existing data hiding method is for anti-forensics, which uses traces of file names of an index entry in an index record when files are deleted in a direcotry. The proposed method in this paper modifies the existing method to make non-admittable ASCII characters for a file name applicable. By improving the existing method, problems of a file creation error due to non-admittable characters are remedied; including the non-admittable 9 characters (i. e. slash /, colon :, greater than >, less than <, question mark ?, back slash ${\backslash}$, vertical bar |, semi-colon ;, esterisk * ), reserved file names(i. e. CON, PRN, AUX, NUL, COM1~COM9, LPT1~LPT9) and two non-admittable characters for an ending character of the file name(i. e. space and dot). Two results of the two message with non-admittable ASCII characters by keyboard inputs show the applicability of the proposed method.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2019.11a
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• pp.58-60
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• 2019

Double JPEG compression detection is one of the most important ways of exposing the integrity of the JPEG image in image forensics. Several methods have been proposed for discriminating against the double JPEG image. In this paper, we propose a new method for restoring the JPEG compressed image and making the detector confused by introducing a Generative Adversarial Network (GAN). First, a generator network is designed for restoring the JPEG compressed image and analyzed the quality. Then, the restored image is tested with the double compression detector for evaluating the robustness of the proposed GAN model. The detection accuracy reduces from 98% to 58%.

• Proceedings of the Korean Society of Computer Information Conference
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• 2008.06a
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• pp.183-188
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• 2008

디지털 포렌식이 활성화 되고 수사에서 활용하는 사례가 증가함에 따라 기업과 개인을 비롯한 범죄혐의자들의 이에 대응하기 위한 기술도 증가하고 있다. 이를 안티포렌식 또는 항포렌식이라고 하는데 이는 디지털 자료의 변조, 파괴, 은닉 등으로 나누어 볼 수 있다. 본 논문에서는 범죄 수사현장에서 필요한 안티포렌식에 대응하는 기술인 위 변조된 데이터 추출 기법, 슬랙 영역의 숨겨진 데이터 추출 기법, 스테카노 그래픽 추출 및 분석 기법, 암호 복호화 기법, 삭제된 데이터 및 파괴된 데이터 복원 기법을 소개하고, 이에 대한 대비책을 제시한다. 본 연구를 통하여 첨단 범죄 수사관들이 안티디지털포렌식에 대한 새로운 디지털 증거의 추출과 분석에 기여하여 컴퓨터 및 첨단 범죄에 대한 디지털 포렌식 기술로 새로운 수사의 방향을 제시 할 수 있을 것이다.

• Journal of the Korea Society of Computer and Information
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• v.24 no.9
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• pp.51-58
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• 2019

Temporal analysis is very useful and important for digital forensics for reconstructing the timeline of digital events. Forgery of a file's timestamp can lead to inconsistencies in the overall temporal relationship, making it difficult to analyze the timeline in reconstructing actions or events and the results of the analysis might not be reliable. The purpose of the timestamp change is to hide the data in a steganographic way, and the other purpose is for anti-forensics. In both cases, the time stamp change tools are requested to use. In this paper, we propose a classification method based on the behavior of the timestamp change tools. The timestamp change tools are categorized three types according to patterns of the changed timestamps after using the tools. By analyzing the changed timestamps, it can be decided what kind of tool is used. And we show that the three types of the patterns are closely related to API functions which are used to develop the tools.

• Proceedings of the Korean Society of Computer Information Conference
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• 2019.07a
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• pp.391-392
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• 2019

본 논문에서는 타임스탬프의 위변조를 위한 안티포렌식의 도구로 사용되는 타임스탬프 변경도구들에 기능에 대하여 디지털 포렌식 관점에서 분석을 수행한다. 타임스탬프 변경도구들로써 수행할 수 있는 타임스탬프 변경작업의 범위와 특징을 찾아본다. NTFS파일시스템에서 사용하는 타임스탬프 변경도구들의 기능상의 분류는 그것들이 변경할 수 있는 타임스탬프 종류와 정밀도를 기준으로 정하고 그 도구들을 사용한 후에 기록된 타임스탬프의 특징들을 디지털 포렌식 관점에서 분석을 수행하기로 한다. 이 연구에서의 분류 형태 중 타입 I은 FileTouch.exe, SKTimeStamp, BulkFileChanger류의 도구들과 타입 II는 timestomp, 타입 III은 SetMACE로 분류하고 각 도구들을 사용한 후에 변경된 타임스탬프들의 특징을 살펴보기로 한다.

• Journal of Information Processing Systems
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• v.18 no.3
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• pp.402-410
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• 2022

Digital data can be manipulated easily, so information related to the timestamp is important in establishing the reliability of the data. The time values for a certain file can be extracted following the analysis of the filesystem metadata or file internals, and the information can be utilized to organize a timeline for a digital investigation. Suppose the reversal of a timestamp is found on a mobile device during this process. In this case, a more detailed analysis is required due to the possibility of anti-forensic activity, but little previous research has investigated the handling and possible manipulation of timestamps on mobile devices. Therefore, in this study, we determine how time values for multimedia files are handled according to the operating system or filesystem on mobile devices. We also discuss five types of timestamps-file created (C), last modified (M), last accessed (A), digitalized (Di), and filename (FN) of multimedia files, and experimented with their operational features across multiple devices such as smartphones and cameras.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.28 no.3
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• pp.625-633
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• 2018

Realm is an open source database developed to replace SQLite, which is commonly used in mobile devices. The data stored in the database must be checked during the digital forensic analysis process for mobile devices because it can help to understand the behavior of the user and whether the mobile device is operating or not. In addition, since the user can intentionally use anti-forensic techniques such as deleting data stored in the database, research on how to recover deleted records is needed. In this paper, we propose a method to recover records that have not been overwritten after deletion based on the analysis of the structure and record and deletion process of the Realm database file.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.27 no.3
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• pp.489-499
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• 2017

MS office is a office software which is widely used in the world. The OOXML format has been applied to the document structure from MS office 2007 to the newest version. In this regard, the method of data concealing, which is a representative anti-forensic act has been researched and developed, so the method of detecting concealed data is very important to the digital forensic investigation. In this paper, we present an improved data concealing method bypassing the previewers detecting methods for OOXML formatted MS office documents. In addition, we show concealment of the internal data like sheets and slides for MS office 2013 Excel and PowerPoint, and suggest an improved detecting algorithm against this data concealing.

• Journal of Digital Forensics
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• v.12 no.3
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• pp.39-54
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• 2018

Recently, discussions for the eradication of illegal shooting have been carried out in a socially-oriented way. The government has established comprehensive measures to eradicate cyber sexual violence crimes such as illegal shooting. Although the social interest in illegal shooting has increased, the illegal film shooting case is evolving more and more due to the development of information and communication technology. Applications that can hide confused videos are constantly circulating around the market and community sites. As a result, field investigators and professional analysts are experiencing difficulties in collecting and analyzing evidence. In this paper, we propose an evidence collection and analysis framework for illegal shooting cases in order to give practical help to illegal shooting investigation. We also proposed a system that can detect hidden applications, which is one of the main obstacles in evidence collection and analysis. We developed a detection tool to evaluate the effectiveness of the proposed system and confirmed the feasibility and scalability of the system through experiments using commercially available concealed apps.