• Journal of the Korean Institute of Telematics and Electronics B
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• v.29B no.7
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• pp.62-69
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• 1992

The conventional BMA is performed with the fixed block size. For better performance at low bitrate, the block size is required to be large in relatively stationary area, while small in moving area. Thus, in this paper, a video coding technique using variable block size model is proposed. It decides the block size based on the degree of local motion defined by the local mean and variance of blocks. Computer simulation shows that the proposed method gives comparable performance to the conventional one with less bits required for motion vector coding.

• Journal of the Korean Institute of Telematics and Electronics
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• v.24 no.6
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• pp.1056-1067
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• 1987

This paper presents a design procedure for building block integrated circuits that is based on the digraph relaxation model. A set of optimization procedure is prosented for a minimum area and routing-fecsible placement of IC building blocks. Chip area optimization is subject to perimeter and area constraints on the component rectangles in the dissection.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.31B no.2
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• pp.45-55
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• 1994

In this paper, a block based image approximation technique using the Self Affine System(SAS) from the fractal theory is suggested. Each block of an image is divided into 4 tiles and 4 affine mapping coefficients are found for each tile. To find the affine mapping cefficients that minimize the error between the affine transformed image block and the reconstructed image block, the matrix euation is solved by setting each partial differential coefficients to aero. And to ensure the convergence of coding block. 4 uniformly partitioned affine transformation is applied. Variable block size technique is employed in order to applynatural image reconstruction property of fractal image coding. Large blocks are used for encoding smooth backgrounds to yield high compression efficiency and texture and edge blocks are divided into smaller blocks to preserve the block detail. Affine mapping coefficinets are found for each block having 16$\times$16, 8$\times$8 or 4$\times$4 size. Each block is classified as shade, texture or edge. Average gray level is transmitted for shade bolcks, and coefficients are found for texture and edge blocks. Coefficients are quantized and only 16 bytes per block are transmitted. Using the proposed algorithm, the computational load increases linearly in proportion to image size. PSNR of 31.58dB is obtained as the result using 512$\times$512, 8 bits per pixel Lena image.

• Journal of Information Processing Systems
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• v.13 no.1
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• pp.184-195
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• 2017

In recent decades, the ad hoc network for vehicles has been a core network technology to provide comfort and security to drivers in vehicle environments. However, emerging applications and services require major changes in underlying network models and computing that require new road network planning. Meanwhile, blockchain widely known as one of the disruptive technologies has emerged in recent years, is experiencing rapid development and has the potential to revolutionize intelligent transport systems. Blockchain can be used to build an intelligent, secure, distributed and autonomous transport system. It allows better utilization of the infrastructure and resources of intelligent transport systems, particularly effective for crowdsourcing technology. In this paper, we proposes a vehicle network architecture based on blockchain in the smart city (Block-VN). Block-VN is a reliable and secure architecture that operates in a distributed way to build the new distributed transport management system. We are considering a new network system of vehicles, Block-VN, above them. In addition, we examine how the network of vehicles evolves with paradigms focused on networking and vehicular information. Finally, we discuss service scenarios and design principles for Block-VN.

• The Transactions of the Korea Information Processing Society
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• v.7 no.5
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• pp.1587-1598
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• 2000

For the object-based video compression at very low bit rate, vieo segmentation is an essential part. In this paper, we propose a temporal video segmentation algorithms for motion pictures which is based on blocks. The algorithm is composed of three steps: (1) the change-detection, (2) the block merging, and (3) the block segmentation. The first step separates the change-detected region from background. Here, a new method for removing the uncovered region without motion estimation is presented. The second step, which is further divided into three substeps, estimates motions for the change-detected region and merges blocks with similar motions. The merging conditions for each substep as criteria are also given. The final step, the block segmentation, segments the boundary block that is excluded from the second step on a pixel basis. After describing our algorithm in detail, several experimental results along the processing order are shown step by step. The results demonstrate that the proposed algorithm removes the uncovered region effectively and produced objects that are segmented well.

• Proceedings of the Korea Information Processing Society Conference
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• 2011.04a
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• pp.986-989
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• 2011

Reversible data hiding is a technique that can embed information into cover media (image, video, voice signal) and can recover the original cover media after extracting the embedded information. In this papa, we propose a new reversible data hiding methods that based on block median preservation and the image local characteristic. By using the median value of a block, a high payload can be got and by considering the image local characteristic, a lot of distortion can be avoided and a high PSNR can be got. In the experiment, our methods can generate better result than the previous reversible data hiding methods.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.26 no.2
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• pp.315-318
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• 2016

In this paper, we present a new preimage attack on MJH, a double-block-length block cipher-based hash function. Currently, the best attack requires $O(2^{3n/2})$ queries for the 2n-bit MJH hash function based on an n-bit block cipher, while our attack requires $O(n2^n)$ queries and the same amount of memory, significantly improving the query complexity compared to the existing attack.

• Journal of Korea Multimedia Society
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• v.5 no.6
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• pp.665-673
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• 2002

In this paper, we introduce cellular automata and propose a new block cipher algorithm based on cellular automata. For the evaluation of performance and security, we compare the results of the proposed algorithm with them of the standard block ciphers such as DES, Rijndael regarding on avalanche effects and processing time, and analyze the differential cryptanalysis for a reduction version of the proposed algorithm. In addition, we perform the statistical tests in FIPS PUB 140-2(Federal Information Processing Standards Publication 140-2) for the output bit sequences of proposed algorithm to guarantee the randomness property.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.2C
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• pp.201-208
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• 2003

The error concealment is very useful technique for real-time communication, such as video conference. In this paper. we propose the error concealment technique to minimize discontinuity of block boundary in consideration of the fact that human visual system is sensitive to discontinuity. The error concealment for each loss block is performed by extended block matching method based on gradient difference. In the simulation result, performance improvement for the proposed technique is on the average 1.32㏈ in comparison with the conventional technique.

• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.329-330
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• 2006

This paper presents a recovery technique for images with block-based corruption by transmission losses. Conventional methods that do not consider edge directions can cause blocked blurring artifacts. In this paper, we present a block recovery scheme using Haar wavelet features. The adaptive selection of neighboring blocks is performed based on the energy ratio f wavelet subbands. The lost blocks are recovered by linear interpolation in the spatial domain using selected block pairs. The proposed directional recovery method is effective for the strong edge because it exploits the varying neighboring blocks adaptively according to the edges and the directional information in the image. The proposed method outperforms the previous methods that used only a predefined set of neighboring blocks.