• The Journal of Korean Institute of Communications and Information Sciences
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• v.17 no.4
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• pp.323-335
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• 1992

In this paper, an adaptive cosine transform coding scheme which incorporate human visual properties into the coding scheme is investigated. Human vision is relatively sensitive to mid-frequency band, and insensitive to very low and very high frequency band. These property was mathematically modelled with MTF(Modulation Transfer Function) through many psychovisual experiment. DCT transforms energy in spatial domain into frequency domain, so can exploit the MTF very efficiently. Another well-known visual characteristics is spatial masking effect that visibility of noise is less in regions of high activity than in regions of low activity. Proposed coding scheme imploys quantization matrix which represent the properties of these spatial frequency response of human vision, and adaptively quality of an image. To compute the activity index of an image block, simple operation is performed in spatial domain, and according to activity index. block of low activity region is more exactly quantized relatively than that of high activity region. Results showed that, at low bit rate, the subjective quality of the reconstructed images by proposed coding scheme is acceptible than that of coding scheme without HVS properties.

• KEPCO Journal on Electric Power and Energy
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• v.2 no.4
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• pp.563-567
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• 2016

In this paper, the chaos-based secure scheme for power line communication is proposed for the first time. A digitalized chaotic generator based Lorenz system is utilized for generating nonlinear dynamic chaotic signal for masking the information signal instead of reported analog chaotic generators. A simple method of encryption and decryption is also given. In order to confirm the feasibility of the proposed scheme, the system is simulated using a simplified encryption/decryption method in Proteus. The gained results from simulation demonstrated that by using the chaos-based security method, the data can be encrypted and easily transmitted through the power line network efficiently.

• Journal of Broadcast Engineering
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• v.6 no.1
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• pp.13-20
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• 2001

In this paper, we propose a new digital audio watermarking scheme In the cepstrum domain. We insert a digital watermark signal Into the cepstral components of the audio signal using a technique analogous to spread spectrum Communications, hiding a narrow band signal in a wade band channel. In our proposed method, we use pseudo-random sequences to watermark the audio signal. The watermark Is then weighted in the cepstrum domain according to the distribution of cepstral coefficients and the frequency masking characteristics of the human auditory system. The proposed watermark embedding scheme minimizes audibility of the watermark signal. and the embedded watermark is robust to mu1tip1e watermarks, MPEG audio ceding and additive noose.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.9B
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• pp.1369-1380
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• 2010

In this paper, we propose the efficient Second-Order Differential Power Analysis attack, which has ability to find significant information such as secret key in the devices consisting IT convergence environment such as Smartgrid, Advanced Metering Infrastructure(AMI) and ZigBee-based home networking service. This method helps to find the secret key easily at a device, even though it uses a countermeasure like masking which makes First-Order DPA attack harder. First, we present the performance results of our implementation which implements practical Second-Order DPA attack using the existing preprocessing function, and analyze it. Then we propose a stronger preprocessing function which overcomes countermeasures like masking. Finally, we analyze the results of the Second-Order CPA attack using proposed preprocessing function and verify that proposed scheme is very threatening to the security fields of IT convergence technology through the experimental results.

• Journal of information and communication convergence engineering
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• v.12 no.4
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• pp.237-245
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• 2014

In this study, software-based countermeasures against a side-channel cryptanalysis of the Rabbit stream cipher were developed using Moteiv's Tmote Sky, a popular wireless sensor mote based on the Berkeley TelosB, as the target platform. The countermeasures build upon previous work by improving mask generation, masking and hiding other components of the algorithm, and introducing a key refreshment scheme. Our contribution brings improvements to previous countermeasures making the implementation resistant to higher-order attacks. Four functional metrics, namely resiliency, robustness, resistance, and scalability, were used for the assessment. Finally, performance costs were measured using memory usage and execution time. In this work, it was demonstrated that although attacks can be feasibly carried out on unprotected systems, the proposed countermeasures can also be feasibly developed and deployed on resource-constrained devices, such as wireless sensors.

• Proceedings of the KSRS Conference
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• 2005.10a
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• pp.26-29
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• 2005

In order to compute cloud coverage statistics over Asian region, an operational scheme for masking cloud-contaminated pixels in Advanced Very High Resolution Radiometer (AVHRR) daytime data was developed, evaluated and presented. Dynamic thresholding was used with channell, 2 and 3 to automatically create a cloud mask for a single image. Then the IO-day cloud coverage imagery was generated over the whole Asian region along with cloud-free composite imagery. Finally the monthly based statistics were computed based on the derived cloud coverage imagery in terms of land cover and country. As a result, it was found that 20-day is required to acquire the cloud free data over the whole Asia using NOAA AVHRR. The to-day cloud coverage and cloud-free composite imagery derived in this research is available via the web-site http://webpanda.iis.u-tokyo.ac.jp/CloudCover/.

• Communications for Statistical Applications and Methods
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• v.9 no.1
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• pp.291-304
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• 2002

This article is concerned with an effective algorithm for the identification of multiple outliers in linear regression. It proposes a hybrid algorithm which employs the least median of squares estimator, instead of the least squares estimator, to construct an Initial clean subset in the stepwise forward search scheme. The performance of the proposed algorithm is evaluated and compared with the existing competitor via an extensive Monte Carlo simulation. The algorithm appears to be superior to the competitor for the most of scenarios explored in the simulation study. Particularly it copes with the masking problem quite well. In addition, the orthogonal decomposition and Its updating techniques are considered to improve the computational efficiency and numerical stability of the algorithm.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07a
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• pp.411-414
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• 2005

We have developed a transflective liquid crystal display (LCD) with a single cell gap and a low twisted nematic (LTN) mode in combination with a self-integrated retardation layer. The retardation layer was made of UV curable liquid crystalline material in one step of photo masking process and has both the homeotropic and the planar parts. The proposed transflective configuration has advantages in a simple fabrication process, and the possibility for a single driving scheme due to the similarity between the transmittance and the reflectance.

• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.345-346
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• 2006

In this paper, we propose the noise suppressor with the psychoacoustic model and wavelet packet transform. The objective of the scheme is to enhance speech corrupted by colored or non-stationary noise. If corrupted noise is colored, subband approach would be more efficient than whole band one. To avoid serious residual noise and speech distortion, we must adjust the Wavelet Coefficient threshold. In this paper, the subband is designed matching with the critical band. And WCT is adapted by noise masking threshold(NMT) and segmental signal to noise ratio(seg_SNR). Consequently this work improve the PESQ-MOS about 0.23 in the case of coded speech.

• The Journal of the Korea institute of electronic communication sciences
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• v.9 no.11
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• pp.1267-1276
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• 2014

As the volume of internet rapidly increases, the number of IPv4 addresses available is quickly declining, while transition to IPv6 is being delayed. As a interim solution, Variable-Length Subnet Masking(VLSM) addressing scheme, which varies the length of each IP address allowing more efficient, is being used. This paper suggests effective example of network based on virtual network with topology designed using VLSM charting rather than usual theoretical approach in VLSM, which allows more efficient use of address space.