• 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 Korea Multimedia Society
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• v.12 no.5
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• pp.717-727
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• 2009

P2P (Peer-to-Peer) network depends on cooperation of peers considerably. However, some peers do not share files at all and only download files. Peers also share low quality files or unpopular files. These selfish behavior of peers is referred to 'free riding'. The free riding of peer may decrease participation of other peers or the system performance. In this paper, we propose an incentive mechanism, called IcMFS (Incentive Mechanism for File Sharing System), which provides the correct use of incentive mechanism using trust peer, computes contribution values referring behavior of peers and rewards peers. The proposed mechanism assigns bandwidth and TTL(Time-To-Live) to a peer and differentiates the use of service. A case study on simulations shows the service differentiation according to the contribution value of peer, the correct use of incentive mechanism using trust peer and the advantage by use of trust peer. To prove the stability of proposed mechanism, we also show the disadvantage that a peer receives from the incorrect use of incentive mechanism.

• The KIPS Transactions:PartB
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• v.9B no.1
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• pp.67-76
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• 2002

MP3 audio format has good quality and high compression rate ; therefore, the use of MP3 format increases. The requirement of keeping the extra information such as author and lyrics in MP3 files increases. And the tagging systems designed to meet this requirement are suggested. ID3 vl tag and Lyrics3 v2 tag are two most widely used tagging systems. But ID3 vl tag and Lyrics3 v2 tag are the last things to arrive when the file is being streamed. Therefore, users cannot get the tag information until the entire audio file is downloaded. Moreover information synchronized with audio stream may lose its feature. In this paper, a system searching and playing audio files based on tag information in MP3 files is implemented. This system solves the problem that the tag information is ignored when an MP3 files is played on internet. An audio object is described in an XML document, and timing and synchronization between elements in that In document is provided in HTML+TIME style using XSL.

• Imaging Science in Dentistry
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• v.30 no.4
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• pp.265-274
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• 2000

Purpose: The aims of the present study are to determine the optimum compression rate in terms of file size reduction and diagnostic quality of the images after compression and evaluate the transmission speed of original or each compressed image. Materials and Methods: The material consisted of 24 extracted human premolars and molars. The occlusal surfaces and proximal surfaces of the teeth had a clinical disease spectrum that ranged from sound to varying degrees of fissure discoloration and cavitation. The images from Digora system were exported in TIFF and the images from conventional intraoral film were scanned and digitalized in TIFF by Nikon SF-200 scanner (Nikon, Japan). And six compression factors were chosen and applied on the basis of the results from a pilot study. The total number of images to be assessed were 336. Three radiologists assessed the occlusal and proximal surfaces of the teeth with 5-rank scale. Finally diagnosed as either sound or carious lesion by one expert oral pathologist. And sensitivity, specificity and k value for diagnostic agreement was calculated. Also the area (Az) values under the ROC curve were calculated and paired t-test and oneway ANOVA test was performed. Thereafter, transmission time of the image files of the each compression level was compared with that of the original image files. Results: No significant difference was found between original and the corresponding images up to 7% (1 : 14) compression ratio for both the occlusal and proximal caries (p<0.05). JPEG3 (1 : 14) image files are transmitted fast more than 10 times, maintained diagnostic information in image, compared with original image files. Conclusion: 1 : 14 compressed image file may be used instead of the original image and reduce storage needs and transmission time.

• Journal of The Korean Astronomical Society
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• v.47 no.3
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• pp.115-122
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• 2014

The New Vacuum Solar Telescope (NVST) is a 1-meter vacuum solar telescope that aims to observe the fine structures of active regions on the Sun. The main tasks of the NVST are high resolution imaging and spectral observations, including the measurements of the solar magnetic field. The NVST has been collecting more than 20 million FITS files since it began routine observations in 2012 and produces maximum observational records of 120 thousand files in a day. Given the large amount of files, the effective archiving and retrieval of files becomes a critical and urgent problem. In this study, we implement a new data archiving system for the NVST based on the Fastbit Not Only Structured Query Language (NoSQL) database. Comparing to the relational database (i.e., MySQL; My Structured Query Language), the Fastbit database manifests distinctive advantages on indexing and querying performance. In a large scale database of 40 million records, the multi-field combined query response time of Fastbit database is about 15 times faster and fully meets the requirements of the NVST. Our slestudy brings a new idea for massive astronomical data archiving and would contribute to the design of data management systems for other astronomical telescopes.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.17 no.4
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• pp.35-41
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• 2017

This paper introduces a new method for storing a private key. This method can be achieved by dividing the private key into "n" pieces by a (k, n) secret sharing method, and then storing each piece into photo files utilizing a steganography method. In this way, a user can restore a private key as long as he can remember the locations of "k" photos among the entire photo files. Attackers, meanwhile, will find it extremely difficult to extract the private key if a user has hidden the pieces of the private key into numerous photo files stored in the system. It also provides a high degree of user convenience, as the user can restore the private key from his memory of k positions among n photo files. Coupled with this, a certain level of security can be guaranteed because the attacker cannot restore a private key, even if he knows k-1 photo file locations.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.5
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• pp.83-90
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• 2012

This paper is a research on the design and implementation of a small real-time radio broadcasting system by using smart phone based on Android. It was designed as the server-client structure, and used the progressive download of HTTP as methods of transferring data to further simplify the system. In order to realize the real-time broadcasting, the original audio source was divided with a short interval and captured to be compressed and stored into files. Then the client receives and plays the compressed files sequentially as it is downloaded. However, this method occurs two problems each of which is the loss of capturing the original source in the server and the discontinuity of playing the files in the client. We solved the problem in the server by separating the thread into two parallel threads of which is each captured and compressed/stored, also by using the double buffering method. The problem in the client was solved using MediaPlayer in Android and the file queue to store the multiple files.

• The Journal of the Korea institute of electronic communication sciences
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• v.13 no.2
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• pp.397-404
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• 2018

As the usage of internet is increasing, a lot of user behavior are written in a log file and the researches and industries using the log files are getting activated recently. This paper uses the Hadoop based on open source distributed computing platform and proposes a customized tourism system by analyzing user behaviors in the log files. The proposed system uses Google Analytics to get user's log files from the website that users visit, and stores search terms extracted by MapReduce to HDFS. Also it gathers features about the sight-seeing places or cities which travelers want to tour from travel guide websites by Octopus application. It suggests the customized cities by matching the search terms and city features. NBP(next bit permutation) algorithm to rearrange the search terms and city features is used to increase the probability of matching. Some customized cities are suggested by analyzing log files for 39 users to show the performance of the proposed system.

• KIPS Transactions on Computer and Communication Systems
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• v.2 no.1
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• pp.43-50
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• 2013

File identification and analysis is an important process of computer forensics, since the process determines which subjects are necessary to be collected and analyzed as digital evidence. An efficient file classification aids in the file identification, especially in case of copyright infringement where we often have huge amounts of files. A lot of file classification methods have been proposed by far, but they have mostly focused on classifying malicious behaviors based on known information. In copyright infringement cases, we need a different approach since our subject includes not only malicious codes, but also vast number of normal files. In this paper, we propose an efficient file classification method that relies on undocumented information in the header of the PE format files. Out method is useful in copyright infringement cases, being applied to any sort of PE format executable file whether the file is malicious, packed, mutated, transformed, virtualized, obfuscated, or not.

• KIPS Transactions on Software and Data Engineering
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• v.9 no.4
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• pp.123-128
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• 2020

As the use of digital devices is becoming more commonplace, digital forensics techniques recover data to collect physical evidence during the investigation. Among them, the file forensics technique recovers deleted files, therefore, it can recover the database by recovering all files which compose the database itself. However, if the record is deleted from the database, the modified record contents will not be restored even if the file is recovered. For this reason, the database forensics technique is required to recover deleted records. Database forensics obtains metadata from database configuration files and recovers deleted records from data files. However, record recovery is difficult if database metadata such as block size cannot be obtained from the database. In this paper, we propose three methods for obtaining block size, which is database metadata. The first method uses the maximum size of free space in the block, and the second method uses the location where the block appears. The third method improves the second method to find the block size faster. The experimental results show that three methods can correctly find the block size of three DBMSes.