• The Journal of the Korea Contents Association
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• v.1 no.1
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• pp.83-92
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• 2001

In this study, we combine information hiding technique with digital contents protection scheme. For providing secure distribution on digital contents, a new paradigm can be proposed after considering both watermarking and fingerprinting techniques. In detail, publicly verifiable digital signature schemes are applied into digital contents. On signing digital copyrights, we can publicly verify its correctness if needed.

• Journal of the Korea Institute of Military Science and Technology
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• v.11 no.3
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• pp.115-122
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• 2008

Wu and Tsai's pixel-value differencing method and Chang and Tseng's side-match method are based on the theory that the number of bits which can be embedded is determined by the degree of the pixel's smoothness, or its proximity to the edge of the image. If pixels are located in the edge area, they may tolerate larger changes than those in smooth areas. However, both methods are subject to the fall off the boundary problem(FOBP). This study proposes a new scheme that can solve the FOBP. The experimental results demonstrate that the proposed method resolves the problem, and achieves a higher image quality index value than other methods.

• Electronics and Telecommunications Trends
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• v.16 no.4 s.70
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• pp.54-66
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• 2001

본 논문은 지금까지 제안 및 개발되어 온 암호화 파일시스템에 대하여 살펴본다. 암호화 파일시스템은 사용자 개개인 혹은 조직 등에서 기밀을 유지하여야 하는 중요한 데이터에 대한 안전한 저장을 목적으로 개발되었다. 암호화 파일시스템의 기능으로는 침입자 혹은 원하지 않는 타인의 접근에 대해 데이터의 기밀성 및 안정성을 보장하고, 암호화 기능의 투명화를 통해 사용의 편리성을 제공하며, 암호화 기능의 수행으로 인해 시스템의 성능이 저하되는 것을 방지하는 것 등이 있다. 현재까지 개발되어 온 대표적인 암호화 파일시스템으로는 Cryptographic File System(CFS), Transparent Cryptographic File System(TCFS), Cryptfs, 그리고 Steganographic File System(StegFS) 등이 있다. 차후에는 분석된 암호화 파일시스템을 통해 좀 더 효율적인 보안성과 이식성을 제공하고, 사용자에 대해 편리성을 제공하는 파일시스템 구조의 설계 및 개발이 필요하다.

• Journal of Korea Society of Industrial Information Systems
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• v.13 no.3
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• pp.23-30
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• 2008

A data hiding method based on least significant bit (LSB) substitution and multi-pixel differencing (MPD) is presented on the proposed method to improve the capacity of the hidden secret data and to provide an imperceptible visual quality. First, a sum of different values for four-pixel sub-block is calculated. The low value of the sum can be located on a smooth block and the high value is located on an edged block. The secret data are hidden into the cover image by LSB method in the smooth block, while MPD method in the edged block. The experimental results show that the proposed method has a higher capacity and maintains a good visual quality.

• Journal of Korea Society of Industrial Information Systems
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• v.13 no.3
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• pp.54-62
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• 2008

For a message hiding technique to be effectual, it needs to have availability, confidentiality and integrity. Steganography is the science of hiding one message within other types of digital contents. In this case, attempt to defeat steganalysis by restoring the statistics of the composite image to resemble that of the cover, these discrepancies expose the fact that hidden communication is happening. In this paper, I present a steganography scheme capable of concealing a piece of secrete information in a host image and base on the technique's OCT, RGB, statistical restoration.

• 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.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.2
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• pp.405-424
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• 2013

In publishing applications, it is advantageous to embed data in halftone images. The CPT scheme (Chen-Pan-Tseng, 2000) is a steganographic data hiding scheme that was proposed for binary images, e.g., facsimiles. The CPT scheme uses a secret key and weight matrix to protect the hidden data and can hide as many as $r={\lfloor}{\log}_2(m{\times}n+1){\rfloor}$ bits of data in the image by changing at most 2 bits in the image. Our proposed scheme also uses a secret key to protect it from being compromised and a weight matrix to increase the data hiding rate. Our scheme improves the performance of the CPT scheme by using the simple principle of splitting each block into two parts. Our proposed scheme is called improved CPT (ICPT) and has a very high embedding capacity compared to previous schemes. Experimental results demonstrate that our proposed scheme generally has higher performance than previous schemes.

• Journal of Korea Multimedia Society
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• v.13 no.7
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• pp.1088-1094
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• 2010

Image authentication algorithms have to discriminate forged contents in the various critical fields of military, medical services, digital documents. They must ensure perceptual invisibility and fragility against malicious attacks. It is desirable that watermarking algorithms support sufficient insertion capacity and blind feature. And, high reliable algorithms that can eliminate false-positive and false-negative errors are needed in the watermark extraction process. In this paper, we control coefficients of high frequency band in a DCT domain and compensate brightness histogram for high reliability. As a result, we found that the proposed algorithm guarantee various requirements such as perceptual invisibility with high PSNR values, fragility, high reliability and blind feature. In addition, experiment results show that the proposed algorithm can be used steganographic applications by sufficient capacity of watermark.

• Journal of Information Processing Systems
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• v.12 no.3
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• pp.525-537
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• 2016

Data hiding is a wide field that is helpful to secure network communications. It is common that many data hiding researchers consider improving and increasing many aspects such as capacity, stego file quality, or robustness. In this paper, we use an audio file as a cover and propose a reversible steganographic method that is modifying the sample values using modulus function in order to make the reminder of that particular value to be same as the secret bit that is needed to be embedded. In addition, we use a location map that locates these modified sample values. This is because in reversible data hiding it needs to exactly recover both the secret message and the original audio file from that stego file. The experimental results show that, this method (measured by correlation algorithm) is able to retrieve exactly the same secret message and audio file. Moreover, it has made a significant improvement in terms of the following: the capacity since each sample value is carrying a secret bit. The quality measured by peak signal-to-noise ratio (PSNR), signal-to-noise ratio (SNR), Pearson correlation coefficient (PCC), and Similarity Index Modulation (SIM). All of them have proven that the quality of the stego audio is relatively high.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.7
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• pp.3353-3370
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• 2016

The way of combination of Product Perfect Codes (PPCs) is based on the theory of short codes constructing long codes. PPCs have larger embedding rate than Hamming codes by expending embedding columns in a coding block, and they have been proven to enhance the performance of the F₅ steganographic method. In this paper, the proposed modified product codes called MPCs are introduced as an efficient way to embed more data than PPCs by increasing 2^r₂-1-r₂ embedding columns. Unlike PPC, the generation of the check matrix H in MPC is random, and it is different from PPC. In addition a simple solving way of the linear algebraic equations is applied to figure out the problem of expending embedding columns or compensating cases. Furthermore, the MPCs over ℤ₄ have been proposed to further enhance not only the performance but also the computation speed which reaches O(n₁+σ). Finally, the proposed ℤ₄-MPC intends to maximize the embedding rate with maintaining less distortion , and the performance surpasses the existing improved product perfect codes. The performance of large embedding rate should have the significance in the high-capacity of covert communication.