• Journal of Digital Contents Society
• /
• v.17 no.6
• /
• pp.461-469
• /
• 2016

A novel steganography based on ternary BCH code with t = 2 is presented in this paper. Proposed method utilizes powerful BCH code with t = 2 for data hiding to the DCT coefficients from JPEG images. The presented data hiding technique uses a proposed look up table approach for searching multiple solutions for ternary BCH code with t = 2. The proposed look up table approach enables fast and efficient search for locations of DCT coefficients, which are necessary to modify for hiding data. Presented data hiding technique is the first steganography technique based on ternary BCH code. Experimental results clearly indicate advantages of using ternary BCH compared to binary BCH.

• Journal of KIISE:Software and Applications
• /
• v.28 no.12
• /
• pp.955-965
• /
• 2001

We propose a systematic method of compiling Haskell based on the spineless Tagless G-machine (STGM) for the Java, Virtual Machine (JVM) We introduce an intermediate language called L-code to identify each micro-operation of the machine by its instruction, Each macro operation of the machine is identified by a binding Each instruction of the L-code can be easily translated into Java statements. After our determination on representation and L-code program from a STG program is translated into Java program according to out compilation rules. Our experiment shows that the execution times of translated benchmarks are competitive compared with those in Haskell interpreter Hugs, particularly when Glasgow Haskell compiler's STG -level optimizations are applied.

• Journal of Communications and Networks
• /
• v.7 no.4
• /
• pp.489-498
• /
• 2005

For better performance over a noisy channel, mobile wireless networks transmit packets with forward error correction (FEC) code to recover corrupt bits without retransmission. The static determination of the FEC code size, however, degrades their performance since the evaluation of the underlying channel state is hardly accurate and even widely varied. Our measurements over a wireless sensor network, for example, show that the average bit error rate (BER) per second or per minute continuously changes from 0 up to $10^{-3}$. Under this environment, wireless networks waste their bandwidth since they can't deterministically select the appropriate size of FEC code matching to the fluctuating channel BER. This paper proposes an adaptive FEC technique called adaptive FEC code control (AFECCC), which dynamically tunes the amount of FEC code per packet based on the arrival of acknowl­edgement packets without any specific information such as signal to noise ratio (SNR) or BER from receivers. Our simulation experiments indicate that AFECCC performs better than any static FEC algorithm and some conventional dynamic hybrid FEC/ARQ algorithms when wireless channels are modeled with two-state Markov chain, chaotic map, and traces collected from real sensor networks. Finally, AFECCC implemented in sensor motes achieves better performance than any static FEC algorithm.

• Journal of Computing Science and Engineering
• /
• v.10 no.2
• /
• pp.39-50
• /
• 2016

In this paper, we present a comparative study of spatial domain features for writer identification and verification with different ink width conditions. The existing methods give high error rates, when comparing two handwritten images with different pen types. To the best of our knowledge, we are the first to design the feature with different ink width conditions. To address this problem, contour based features were extracted using a chain code method. To improve accuracy at higher levels, we considered histograms of chain code and variance in bins of histogram of chain code as features to discriminate handwriting samples. The system was trained and tested for 1,000 writers with two samples using different writing instruments. The feature performance is tested on our newly created dataset of 4,000 samples. The experimental results show that the histogram of chain code feature is good compared to other methods with false acceptance rate of 11.67%, false rejection rate of 36.70%, average error rates of 24.18%, and average verification accuracy of 75.89% on our new dataset. We also studied the effect of amount of text and dataset size on verification accuracy.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2013.05a
• /
• pp.586-589
• /
• 2013

In this paper, the proposed scheme is STBC system combined with convolutional code to ensure the reliability of data transmission for a high rate wireless communication. In addition, this scheme uses a modified viterbi algorithm in order to get a high system gain when data is transmitted. Because we combine STBC and comvolutional code, the proposed scheme can get a diversity gain of STBC and coding gain of convolutional code at the same time. Unlike existing viterbi docoding algorithm using Hamming distance in order to calculate branch matrix, the modified viterbi algorithm uses Euclidean distance value between received symbol and reference symbol. To analyze the system proposed, it was simulated by changing the constraint length of the convolutional code and the number of transmit and receive antennas of STBC.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.12 no.9
• /
• pp.4560-4575
• /
• 2018

Since smartphone contains various personal data, security is one of the important aspects in smartphone technologies. Up to now, various authentication techniques have been proposed to protect smartphones. The pattern lock on the Android system is one of the most widely used authentication methods for low-cost devices but it is known to be vulnerable to smudge attack or shoulder surfing attack. LG's smartphone uses its own technique, which is called "Knock Code." The knock code completes the authentication by touching the user defined area in turn on the screen. In this paper, we propose the new, enhanced version of knock code by adding the sliding operation and by using flexible area recognition. We conducted security analysis, which shows that under the same password size, the search space is overwhelmingly larger than the original algorithm. Also, by using the sliding operation, the proposed scheme shows resilience against smudge attacks. We implemented the prototype of our scheme. Experimental results show that compared with the original Knock Code and Android pattern lock, our scheme is more convenient while providing better security.

• Proceedings of the Korean Nuclear Society Conference
• /
• 1998.05a
• /
• pp.641-646
• /
• 1998

In order to enhance the dynamic and interactive simulation capability of a system thermal hydraulic code for nuclear power plant, applicability of flow network models in SINDA/FLUIN $T^{™}$ has been tested by modeling feedwater system and coupling to DSNP which is one of a system thermal hydraulic simulation code for a pressurized heavy water reactor. The feedwater system is selected since it is one of the most important balance of plant systems with a potential to greatly affect the behavior of nuclear steam supply system. The flow network model of this feedwater system consists of condenser, condensate pumps, low and high pressure heaters, deaerator, feedwater pumps, and control valves. This complicated flow network is modeled and coupled to DSNP and it is tested for several normal and abnormal transient conditions such turbine load maneuvering, turbine trip, and loss of class IV power. The results show reasonable behavior of the coupled code and also gives a good dynamic and interactive simulation capabilities for the several mild transient conditions. It has been found that coupling system thermal hydraulic code with a flow network code is a proper way of upgrading simulation capability of DSNP to mature nuclear plant analyzer (NPA).

• Journal of the Institute of Electronics Engineers of Korea SP
• /
• v.39 no.5
• /
• pp.504-512
• /
• 2002

This paper presents a new subfield method that can alleviate the visual artifact called the dynamic false contour (DFC), which occurs on plasma display panels. Nothing that the DFC is caused by the difference of time intervals between the adjacent subfields, we propose a constant slope code, in which the differences are maintained to be constant. Also, we propose a subfield code that can minimize the mean absolute error, considering the trade-off between the peak magnitude of the error and its duration. We will show that the proposed subfield method maintains an adequate performance in the view point of the human visual system, since the bound of the errors increases with the gray scale.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.48 no.6
• /
• pp.22-27
• /
• 2011

This paper presents an efficient technique to reduce PN code acquisition time considerably by adjusting threshold values in direct sequence spread spectrum (DS-SS) systems. The proposed algorithm employs a pre-dump mode prior to a search mode, and the pre-dump mode determines threshold values of both search and verification modes depending on its correlation energy, which can improve not only the rejection performance of false code phases in the search mode but also that in the verification mode. The proposed method can reduce the mean code acquisition time by about 40% without increase of hardware costs compared with the conventional technique.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.54 no.6
• /
• pp.11-16
• /
• 2017

Multi-level holographic data storage requires modulation codes for avoiding two dimensional inter-symbol interference (2D-ISI). Modulation codes can remove the fatal ISI pattern of neighboring the largest and the smallest symbols. In this paper, we propose a 4-level 4/6 modulation code and its trellis encoding for error correction. The proposed 4/6 modulation code prevents that the symbol 0 and 3 are not adjacent in any direction. Also, we compare the proposed modulation code with the same code rate modulation codes for four-level holographic data storage.