• Proceedings of the Korea Institutes of Information Security and Cryptology Conference
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• 1995.11a
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• pp.244-253
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• 1995

화상 내의 중복도를 의미하는 자기 상사성(self-similarity)을 제거하여 화상압출을 수행하는 프랙탈 화상압축 방식에 대한 연구가 최근에 활발히 진행되고 있다. 프랙탈 화상압축은 비가역 부호화 방식으로 화상을 일정블럭으로 분할하여 상사영역을 탐색하고 그 상사영역에 대한 파라메터를 압축을 위한 정보로 저장한다 전송하고자 하는 데이터가 화상과 기밀 데이터의 2가지가 혼재할 경우 일반적으로 각 데이터를 개별적으로 압축하고 전송가게 된다. 또한, 화상의 특징을 이용하여 기밀 데이터를 화상 내에 몰래 집어넣은 후, 그 화상을 압축하여 전송하는 방식이 있다. 본 논문에서는 이러한 방식과는 달리 기밀 데이터를 프랙탈 화상압축을 수행함과 동시에 예측부호화를 이용하여 제 3자가 인식할 수 없는 잡음의 형태로 합성하는 방법에 대하여 고찰하고 시뮬레이션 결과를 나타낸다.

• Annual Conference of KIPS
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• 2013.11a
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• pp.842-844
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• 2013

범죄예방이나 위급사항에 대한 대응 등 CCTV의 다양한 필요성에 따라 CCTV를 통합관리하는 CCTV 통합관제 센터가 늘어나고 있다. 행정안전부는 2015년까지 전국 시군구에 CCTV 통합관제센터 구축을 추진하고 있어 앞으로도 계속적으로 증가할 예정이다. 하지만 CCTV관제센터는 증가하고 있음에도 이를 관리할 전문 모니터링 요원이 부족하며, 동시에 이들이 영상정보를 개인의 호기심이나 이득을 위해 사용하는 일이 발생 할 수 있다. 본 논문을 Shamir's Secret Sharing 방법을 이용하여 암호화된 키를 분배하고 요청에 따라 일정 수 이상의 분배키가 모이면 영상 열람권한을 주는 방식으로 설계 하여 관리자가 임의로 영상정보에 접근하는 상황을 방지하였다. 또한 암호키와 랜덤한 값을 이용한 세션키 생성 등을 통해 다양한 보안위협에도 대응하였다.

• Journal of Information Processing Systems
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• v.20 no.1
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• pp.24-37
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• 2024

To address the requirement for high-speed encryption of large amounts of data, this study improves the widely adopted cipher block chaining (CBC) mode and proposes a controllable parallel cipher block chaining (CPCBC) block cipher mode of operation. The mode consists of two phases: extension and parallel encryption. In the extension phase, the degree of parallelism n is determined as needed. In the parallel encryption phase, n cipher blocks generated in the expansion phase are used as the initialization vectors to open n parallel encryption chains for parallel encryption. The security analysis demonstrates that CPCBC mode can enhance the resistance to byte-flipping attacks and padding oracle attacks if parallelism n is kept secret. Security has been improved when compared to the traditional CBC mode. Performance analysis reveals that this scheme has an almost linear acceleration ratio in the case of encrypting a large amount of data. Compared with the conventional CBC mode, the encryption speed is significantly faster.

• Journal of Broadcast Engineering
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• v.22 no.5
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• pp.643-651
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• 2017

Steganography is one of information hiding technologies and discriminated from cryptography in that it focuses on avoiding the existence the hidden information from being detected by third parties, rather than protecting it from being decoded. In this paper, as an image steganography method which uses images as media, we propose a new block matching method that embeds information into the discrete wavelet transform (DWT) domain. The proposed method, based on a statistical analysis, reduces loss of embedding capacity due to inequable use of candidate blocks. It works in such a way that computes the variance of each candidate block, preserves candidate blocks with high frequency components while reducing candidate blocks with low frequency components by compressing them exploiting the k-means clustering algorithm. Compared with the previous block matching method, the proposed method can reconstruct secret images with similar PSNRs while embedding higher-capacity information.

• Journal of the Institute of Convergence Signal Processing
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• v.20 no.4
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• pp.205-211
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• 2019

Steganalysis is a technique that aims to detect and recover data hidden by steganography. Steganalytic methods detect hidden data by analyzing visual and statistical distortions caused during data embedding. However, for recovering the hidden data, they need to know which steganographic methods the hidden data has been embedded by. Therefore, we propose a hierarchical convolutional neural network (CNN) structure that identifies a steganographic method applied to an input image through multi-level classification. We trained four base CNNs (each is a binary classifier that determines whether or not a steganographic method has been applied to an input image or which of two different steganographic methods has been applied to an input image) and connected them hierarchically. Experimental results demonstrate that the proposed hierarchical CNN structure can identify four different steganographic methods (LSB, PVD, WOW, and UNIWARD) with an accuracy of 79%.

• Journal of Convergence for Information Technology
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• v.7 no.5
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• pp.137-148
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• 2017

Recently, researchers are actively addressed to utilize Unmanned Aerial Vehicles(UAV) for military and industry applications. One of these applications is to trace the preceding flight when it is necessary to track the route of the suspicious reconnaissance aircraft in secret, and it is necessary to estimate the attitude of the target flight such as Roll, Yaw, and Pitch angles in each instant. In this paper, we propose a method for estimating in real time the attitude of a target aircraft using the video information that is provide by an external camera of a following aircraft. Various image processing methods such as color space division, template matching, and statistical methods such as linear regression were applied to detect and estimate key points and Euler angles. As a result of comparing the X-plane flight data with the estimated flight data through the simulation experiment, it is shown that the proposed method can be an effective method to estimate the flight attitude information of the previous flight.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.24 no.11
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• pp.1507-1518
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• 2020

High-quality images have a lot of information, so sensitive data is stored by encryption for private company, military etc. Encrypted images can only be decrypted with a secret key, but the original data cannot be retained when attacked by the Shear attack and Noise pollution attack techniques that overwrite some pixel data with arbitrary values. Important data is the more necessary a countermeasure for the recovery method against attack. In this paper, we propose a random number generator PingPong256 and a shuffling method that rearranges pixels to resist Shear attack and Noise pollution attack techniques so that image and video encryption can be performed more quickly. Next, the proposed PingPong256 was examined with SP800-22, tested for immunity to various noises, and verified whether the image to which the shuffling method was applied satisfies the Anti-shear attack and the Anti-noise pollution attack.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.15 no.4
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• pp.217-222
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• 2022

Information plays an important role in modern society. Most of the information is processed and moved in the digital space. In cyberspace, confidential communication based on resistance and security is fundamental. It is essential to protect the information sent and received over the network. However, information may be leaked and forged by unauthorized users. The effectiveness of the existing protection system decreases as an innovative technique is applied to identify the communication contents by a third party. Steganography is a technique for inserting secret information into a specific area of a medium. Stegganography and steganalysis techniques are at odds with each other. A new and sophisticatedly implemented system is needed to cope with the advanced steganalysis. To enhance step-by-step diffusion and irregularity, I propose a hybrid implementation technique of image steganography for Hangul messages based on layered encryption and variable ShiftRows. PSNR was calculated to measure the proposed steganography efficiency and performance. Compared to the basic LSB technique, it was shown that the diffusion and randomness can be increased even though the PSNR decreased by 1.45%.

• Journal of KIISE:Computer Systems and Theory
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• v.36 no.2
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• pp.73-86
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• 2009

This paper proposes a new data hiding scheme for binary image authentication with minimizing the distortion of host image. Based on the Hamming-Code-Based data embedding algorithm, the proposed scheme makes it possible to embed authentication information into host image with only flipping small number of pixels. To minimize visual distortion, the proposed scheme only modifies the values of the flippable pixels that are selected based on Yang et al's flippablity criteria. In addition to this, by randomly shuffling the bit-order of the authentication information to be embedded, only the designated receiver, who has the secret key that was used for data embedding, can extract the embedded data. To show the superiority of the proposed scheme, the two measurement metrics, the miss detection rate and the number of flipped pixels by data embedding, are used for the comparison analysis between the proposed scheme and the previous schemes. As a result of analysis, it has been shown that the proposed scheme flips smaller number of pixels than the previous schemes to embed the authentication information of the same bit-length. Moreover, it has been shown that the proposed scheme causes smaller visual distortion and more resilient against recent steg-analysis attacks than the previous schemes by the experimental results.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.23 no.6
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• pp.1037-1047
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• 2013

As damages from phishing have been increased, many anti-phishing solutions and related researches have been studied. Anti-phishing solutions are often built in web-browsers or provided as security toolbars. Other types of solutions are also developed such as email-filtering and solutions strengthening server authentication via secret image sharing. At the same time, researchers have tried to see the reasons why phishing works and how effective anti-phishing solutions are. In this paper, we review relevant anti-phishing solutions, their techniques and other phishing-related researches. Based on these, we summarize recommended ways to improve anti-phishing solutions and suggest the future directions to study to protect users from phishing attacks.