• 한국HCI학회:학술대회논문집
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• 2006.02a
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• pp.931-936
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• 2006

This paper presents different issues of the real-time compression algorithms without compromising the video quality in the distributed environment. The theme of this research is to manage the critical processing stages (speed, information lost, redundancy, distortion) having better encoded ratio, without the fluctuation of quantization scale by using IP configuration. In this paper, different techniques such as distortion measure with searching method cover the block phenomenon with motion estimation process while passing technique and floating measurement is configured by discrete cosine transform (DCT) to reduce computational complexity which is implemented in this video codec. While delay of bits in encoded buffer side especially in real-time state is being controlled to produce the video with high quality and maintenance a low buffering delay. Our results show the performance accuracy gain with better achievement in all the above processes in an encouraging mode.

• Proceedings of the KIEE Conference
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• 2005.05a
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• pp.161-163
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• 2005

In this paper, we propose an efficient motion vector recovery algorithm for the new coding standard H.264, which makes use of the Lagrange interpolation formula. In H.264/AVC, a 16$\times$16 macroblock can be divided into different block shapes for motion estimation, and each block has its own motion vector. In the natural video the motion vector is likely to move in the same direction, hence the neighboring motion vectors are correlative. Because the motion vector in H.264 covers smaller area than previous coding standards, the correlation between neighboring motion vectors increases. We can use the Lagrange interpolation formula to constitute a polynomial that describes the motion tendency of motion vectors, and use this polynomial to recover the lost motion vector. The simulation result shows that our algorithm can efficiently improve the visual quality of the corrupted video.

• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.5-6
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• 2006

iSCSI is a block-oriented storage access protocol that enables a user to recognize a remote storage as their own local block device through general TCP/IP networks. This paper presents an alternative approach to overcome the limited storage space of mobile devices based on the iSCSI initiator driver in IPv6 environment, which was originally designed for wired networks.

• The KIPS Transactions:PartC
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• v.12C no.5 s.101
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• pp.765-772
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• 2005

In this paper, we propose E-mail sending-server authorization method using a distance estimation algorithm between W addresses to check whether the E-mail sending server is registered in the domain of mail sending server or belongs to the domain for filtering spam mail. This method utilizes the distance between the IP address of sending server and IP addresses registered in the DNS to figure out that the E-mail sending server exists in the domain to filter spam mail. The experimental result of applying the proposed algorithm to sample E-mails gathered in a large size laboratory says that 88 percents of legitimate E-mails and only 10 percents of spam mails are sent by servers in the same domains of senders. The algorithm may be effectively used to block spam mails sent by servers outside of the domains of mail senders. It may be also hired as a temporary E-mail protecting system until the standard E-mail authorization protocol is fully deployed.

• Management Science and Financial Engineering
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• v.14 no.1
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• pp.91-96
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• 2008

Robust knapsack problem appears when dealing with data uncertainty on the knapsack constraint. This note presents a generalization of the cover inequality for the problem with its lifting procedure. Specifically, we show that the lifting can be done in a polynomial time as in the usual knapsack problem. The results can serve as a building block in devising an efficient branch-and-cut algorithm for the general robust (0, 1) IP problem.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.3A
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• pp.368-376
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• 2006

This paper describes a Fcore_GenSim(Parameterized FFT Core Generation & Simulation Program), which can be used as an essential If(Intellectual Property) in various OFDM modem designs. The Fcore_Gensim is composed of two parts, a parameterized core generator(PFFT_CoreGen) that generates Verilog-HDL models of FFT cores, and a fixed-point FFT simulator(FXP_FFTSim) which can be used to estimate the SQNR performance of the generated cores. The parameters that can be specified for core generation are FFT length in the range of 64 ~2048-point and word-lengths of input/output/internal/twiddle data in the range of 8-b "24-b with 2-b step. Total 43,659 FFT cores can be generated by Fcore_Gensim. In addition, CBFP(Convergent Block Floating Point) scaling can be optionally specified. To achieve an optimized hardware and SQNR performance of the generated core, a hybrid structure of R2SDF and R2SDC stages and a hybrid algorithm of radix-2, radix-2/4, radix-2/4/8 are adopted according to FFT length and CBFP scaling.

• KIISE Transactions on Computing Practices
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• v.23 no.6
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• pp.350-358
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• 2017

Spill of personal information using a stolen ID and password that recently occurred in large enterprises and portal web site such as Nate, Auction, National Agricultural Cooperative Federation, suggesting the importance of protecting personal information. By managing access to user accounts in real time, users will be able to block access before personal information is leaked. Therefore, In this paper, we propose a method to prevent spill of personal information that may occur when connected to others by using an authorized ID and password from portals. Specifically, we offer a mobile status control app that controls the logged status of user account in real time to view login status information to user by visualization and information about specific time and IP address. Also, we propose a method for detecting and blocking duplicated login that connect via IP address change.

• Journal of Advanced Navigation Technology
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• v.18 no.6
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• pp.600-608
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• 2014

In this paper, CABAC H/W module is developed using co-design method. After entire H.264/AVC encoder was developed with C using reference SW(JM), CABAC H/W IP is developed as a block in H.264/AVC encoder. Context modeller of CABAC is included on the hardware to update the changed value during binary encoding, which enables the efficient usage of memory and the efficient design of I/O stream. Hardware IP is co-operated with the reference software JM of H.264/AVC, and executed on Virtex-4 FX60 FPGA on ML410 board. Functional simulation is done using Modelsim. Compared with existing H/W module of CABAC with register-level design, the development time is reduced greatly and software engineer can design H/W module more easily. As a result, the used amount of slice in CABAC is less than 1/3 of that of CAVLC module. The proposed co-design method is useful to provide hardware accelerator in need of speed-up of high efficient video encoder in embedded system.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2012.10a
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• pp.99-102
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• 2012

An image scaler is a IP used in a image processing block of display devices to adjust image size. Proposed image scaler adopts line memories instead of a conventional method using a frame memory. This method reduced hardware resources and enhanced data precision by using shift operations that number is multiplied by $2^m$ and divided again at final stage for scaling. Also image scaler increased efficiency of IP by using serial divider to calculate parameters by itself. Parameters used in image scaling is automatically produced by it. Suggested methods are designed by Verilog HDL and implemented with Xilinx Vertex-4 XC4LX80 and ASIC using TSMC 0.18um process.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.5
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• pp.1445-1462
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• 2012

While botnets are used for various malicious activities, it is well known that they are widely used for email spam. Though the spam filtering systems currently in use block IPs that send email spam, simply blocking the IPs of zombie PCs participating in a botnet is not enough to prevent the spamming activities of the botnet because these IPs can easily be changed or manipulated. This IP blocking is also insufficient to prevent crimes other than spamming, as the botnet can be simultaneously used for multiple purposes. For this reason, we propose a system that detects botnets and zombie PCs based on email spam analysis. This study introduces the concept of "group pollution level" - the degree to which a certain spam group is suspected of being a botnet - and "IP pollution level" - the degree to which a certain IP in the spam group is suspected of being a zombie PC. Such concepts are applied in our system that detects botnets and zombie PCs by grouping spam mails based on the URL links or attachments contained, and by assessing the pollution level of each group and each IP address. For empirical testing, we used email spam data collected in an "email spam trap system" - Korea's national spam collection system. Our proposed system detected 203 botnets and 18,283 zombie PCs in a day and these zombie PCs sent about 70% of all the spam messages in our analysis. This shows the effectiveness of detecting zombie PCs by email spam analysis, and the possibility of a dramatic reduction in email spam by taking countermeasure against these botnets and zombie PCs.