• Journal of the Korea Institute of Information Security & Cryptology
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• v.24 no.2
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• pp.319-325
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• 2014

Since smart phones or tablet PCs have been widely used recently, the users can create and edit documents anywhere in real time. If the input and edit flows of documents can be traced, it can be used as evidence in digital forensic investigation. The typical document application is the MS(Microsoft) Office. As the MS Office applications consist of two file formats that Compound Document File Format which had been used from version 97 to 2003 and OOXML(Office Open XML) File Format which has been used from version 2007 to now. The studies on MS Office files were for making a decision whether the file has been tampered or not through detection of concealed items or analysis of documents properties so far. This paper analyzed the input order of text cells on MS Excel files and shows how to figure out what cell is the last edited in digital forensic perspective.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.29 no.4
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• pp.835-845
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• 2019

File Carving is a technique for attempting to recover a file without metadata, such as a formated storage media or a damaged file system, and generally looks for a specific header / footer signature and data structure of the file. However, file carving is faced with the problem of recovering fragmented files for a long time, and it is very important to propose a solution for digital forensics because important files are relatively fragmented. To overcome these limitations, various carving techniques and tools are continuously being developed, and data sets from various researches and institutions are provided for functional verification. However, existing data sets are ineffective in verifying tools because of their limited environmental conditions. Therefore, this paper refers to the importance of fragmented file carving and develops 16 images for carving tool verification based on scenarios. The developed images' carving rate and accuracy of each media is shown through Foremost which is well known as a commercial carving tool.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2011.05a
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• pp.660-663
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• 2011

The file security function, which this paper suggests, restricts the access of an unauthorized users by using password algorithm and saving file. Saved files that are encrypted are read by decrypting them with decryption algorithm. These features are user interface to design the program for user friendly. The security function implements both file encryption and decryption programs and tests whether the experiment works or not. In addition, when a decryption is progressed and the settings of between decryption and encryption are different each other, the security function also checks the possibility of decryption. We can enhance the security on important files stored in Windows servers or personal computers by developing this program.

• The Journal of the Korea institute of electronic communication sciences
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• v.14 no.1
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• pp.243-250
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• 2019

In this paper, we develop a Secure File Management Security(: SFMS) based on media in a cloud environment to encrypt and decrypt cloud data on a computer using a Bluetooth - based cryptographic module. The Bluetooth cipher module makes it easy to browse files stored in the cloud, but it is never possible to browse without a module. It is a solution that fundamentally blocks the problems such as hacking and leakage of personal data that have recently become an issue.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.9 no.2
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• pp.49-60
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• 1999

IC 카드의 하드웨어적인 제약으로 대부분의 IC 카드는 대칭키 알고리즘을 사용하고 있지만 IC 카드 하드웨어 제조 기술의 발전으로 앞으로는 보안성이 우수한 비대 칭키 알고리즘이 많이 사용될 것이다. 그리고 IC 카드의 가장 큰 제약적 중 하나는 메모리 용량의 한계이다. 따라서 보안상 안전하면서도 메모리를 적게 사용하는 IC 카드 운영체제의 구현을 중요한 문제이다. 그래서 본 논문에서는 다양한 종류의 키 알고리즘을 수용할 수 있는 키 파일 탐색 기법을 제안하였다. 또한 데이터 파일 헤더에 잠금 필드를 삽입하여 보안성을 향상시켰으며 메모리 사용량을 줄일 수 있도록 데이터 파일 헤더만을 이용한 파일 탐색 기법과 자유 공간 탐색 기법을 제안하였다. Because of the evolution of IC card hardware fabrication technologies IC card will be able to accept asymmetric key encryption algorithm in the future. One of the most restrictive points of IC card is memory capacity. Therefore it is an important problem to design a secure IC card operating system using memory in small. In this paper we proposed a key file search mechanism using a key length field inserted in a key file header structure. The key file search mechanism makes IC card execute any key-based encryption algorithm. In addition we proposed inserting a lock field in data file header structure. The lock field intensifies the security of a data file. Finally we proposed a data file search mechanism and free space search mechanism using only data file header. The file system using these mechanisms spends smaller memory than that using a file description table and record of unallocated space.

• The KIPS Transactions:PartC
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• v.10C no.7
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• pp.929-936
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• 2003

We Propose the Suity Cryptography File System to encrypt or decrypt a plaintext or an encrypted tort by using the dynamic linking mechanism In the Linux kernel. The dynamic linking mechanism gives the flexibility of the kernel without changing the kernel. The Sorority Cryptography File System uses the blowfish algorithm to encrypt or decrypt a data. To overcome the overhead of the key server, I use key generating algorithm which is installed in the same Security Cryptography File System. The Security Cryptography file System is fitted into the Linux system.

• Journal of Convergence for Information Technology
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• v.9 no.1
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• pp.142-150
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• 2019

This study is a file management security system that encrypts and decrypts computer and cloud data by using Bluetooth based cryptographic module. It is a necessary solution in terms of abuse of personal information and protection of social and national information. We developed H/W and S/W for SFMS(: Safe File Management Security) related Bluetooth module in cloud environment and implemented firmware development, encryption key generation and issuance, client program for system mobile and key management system. In the terminal internal encryption and decryption, SFMS was developed to ensure high security that the hacking itself is not possible because key values exist separately for each file.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.25 no.6
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• pp.1485-1494
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• 2015

Traditionally, data hiding has been done mainly in such a way that insert the data into the large-capacity multimedia files. However, the document files of the previous versions of Microsoft Office 2003 have been used as cover files as their structure are so similar to a File System that it is easy to hide data in them. If you open a compound-document file which has a secret message hidden in it with MS Office application, it is hard for users who don't know whether a secret message is hidden in the compound-document file to detect the secret message. This paper presents an analysis of Compound-File Binary Format features exploited in order to hide data and algorithms to detect the data hidden with these exploits. Studying methods used to hide data in unused area, unallocated area, reserved area and inserted streams led us to develop an algorithm to aid in the detection and examination of hidden data.

• Journal of the Korea Convergence Society
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• v.10 no.3
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• pp.7-14
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• 2019

With the development of information and communication technology, we have been able to access and manage documents containing corporate information anytime and anywhere using smart devices. As the work environment changes to smart work, the scope of information distribution is expanded, and more efforts are needed to manage security. This paper proposes a file sharing system that enables users who have smart devices to manage and share files through mutual cooperation. Proposed file sharing system, the user can add a partner to share files with each other when uploading files kept by spliting the part of the file and the other uses an algorithm to store on the server. After converting the file to be uploaded to base64, it splits it into encrypted files among users, and then transmits it to the server when it wants to share. It is easy to manage and control files using dedicated application to view files and has high security. Using the system developed with proposed algorithm, it is possible to build a system with high efficiency even for SMEs(small and medium-sized enterprises) that can not pay much money for security.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.29 no.4
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• pp.859-866
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• 2019

Cybersecurity attack targeting a specific user is rising in number, even enterprises are trying to strengthen their cybersecurity. Network segmentation environment where public network and private network are separated could block information coming from the outside, however, it is unable to control outside information for business efficiency and productivity. Even if enterprises try to enhance security policies and introduce the network segmentation system and a solution incorporating CDR technology to remove unnecessary data contained in files, it is still exposed to security threats. Therefore, we suggest a system that uses file format conversion to transmit a secure file in the network separation environment. The secure file is converted into an image file from a document, as it reflects attack patterns of inserting malicious code into the document file. Additionally, this paper proposes a system in the environment which functions that a document file can keep information for incident response, considering forensic readiness.