• Journal of the Korea Society of Computer and Information
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• v.13 no.4
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• pp.169-175
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• 2008

The existing block encryption algorithms have been designed for the encryption key value to be unchanged and applied to the round functions of each block. and enciphered. Therefore, it has such a weak point that the plaintext or encryption key could be easily exposed by differential cryptanalysis or linear cryptanalysis, both are the most powerful methods for decoding block encryption of a round repeating structure. Dynamic cipher has the property that the key-size, the number of round, and the plaintext-size are scalable simultaneously. Dynamic network is the unique network satisfying these characteristics among the networks for symmetric block ciphers. We analyze the strength of Dynamic network for meet-in-the-middle attack, linear cryptanalysis, and differential cryptanalysis. Also, In this paper we propose a new network called Dynamic network for symmetric block ciphers.

• Journal of the Institute of Convergence Signal Processing
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• v.3 no.3
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• pp.36-40
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• 2002

In this paper, we proposed a digital watermarking method based on the edge-wavelet transform to protect digital contents copyrights. We find out the optimal watermark insertion region and the proper amount of watermark in order to satisfy robustness and imperceptibility against various attacks such as noise, compression, collusion, clipping, scaling. Especially through this experiment, we could find out the adequate location of watermark insertion and proper amount of watermark and it is also viewed to satisfy robustness and imperceptibility in the lower frequency region with small watermark quantity.

• The KIPS Transactions:PartB
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• v.9B no.4
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• pp.459-464
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• 2002

In this paper, we propose a private digital watermarking method based on a wavelet transform to protect digital contents copyrights. We find out the optimal watermark insertion region and the optimal amount of watermark in order to satisfy robustness and imperceptibility against various attacks such as noise, compression, collusion, clipping, scaling to transfer the contents safely. Through this experiment, we could find out the adequate location of watermark insertion and proper amount of watermark, and transfer the watermarked image safely.

• Journal of Advanced Navigation Technology
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• v.16 no.1
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• pp.8-15
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• 2012

This paper on the assumption that the target is stationary and the velocity of missile is fixed value. In three dimensional space. Using flight path angle to simultaneous control impact-time-and-angle base on a homing guidance law. The independent variable in the nonlinear engagement model is the flight path angle of the missile. The propose homing guidance law can see the controllability of impact-time-and-angle. And also can see the processing of the missile arrive at the target. It is applied to several salvo attack scenarios. The performance of the proposed guidance law is verified by simulations.

• Convergence Security Journal
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• v.17 no.1
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• pp.3-13
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• 2017

As security log plays important roles in various fields, the integrity of log data become more and more important. Especially, the stored log data is an immediate target of the intruder to erase his trace in the system penetrated. Several theoretical schemes to guarantee the forward secure integrity have been proposed, even though they cannot provide the integrity of the log data after the system is penetrated. Authentication tags of these methods are based on the linear-hash chain. In this case, it is difficult to run partial validation and to accelerate generating and validating authentication tags. In this paper, we propose a log authentication mechanism, based on Mekle Tree, which is easy to do partial validation and able to apply multi threading.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.7C
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• pp.726-734
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• 2005

Traditional watermarking technologies are symmetric method which embedding and detection keys are the same. Although the symmetric watermarking method is easy to detect the watermark, this method has weakness against to malicious attacks remove or modify the watermark information when the symmetric key is disclosure. Recently, the asymmetric watermarking method that has different keys to embed and detect is watched by several researchers as a next generation watermarking technology. In this paper, hybrid asymmetric watermarking algorithm is proposed. This algorithm is composed of correlation detection method and critical criteria method. Each method can be individually used to detect watermark from a watermarked content. Hybrid asymmetric detection is complement between two methods, and more feasible than when each method is used respectively, Private key and public key are generated by secure linear transformation and specific matrix. As a result, we have proved the proposed algorithm is secured than symmetric watermarking algorithms. This algorithm can expand to multi bits embedding watermark system and is robust to JPEG and JPEG2000 compression.

• Journal of the Institute of Electronics Engineers of Korea TE
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• v.39 no.3
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• pp.21-27
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• 2002

The digital watermarking methods have been proposed as a solution for solving the illegal copying and proof of ownership problems in the context of multimedia data. But it is still difficult to have been overcame the problem of the protection of property to multimedia data, such as digital images, digital video, and digital audio. This paper describes a watermarking algorithm that embeds non-linearly audio logo watermark data which is converted from audio signal of the ownership in the components of pixel intensities in an original image and that insists of ownership by hearing the audio signal transformed from the extracted audio logo through the speaker. Experimental results show that our algorithm using audio logo proposed in this paper is robust against attacks such as particularly lossy JPEG image compression. 

• Journal of the Korea Computer Industry Society
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• v.10 no.4
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• pp.167-176
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• 2009

In this paper, we propose an improved SHACAL-1 of the same encryption and decryption with a simple symmetric layer. SHACAL-1 has 4 rounds, and each round has 20 steps. Decryption is becoming inverse function of encryption, In this paper, we proposed SHACAL-1 are composed of the first half, symmetry layer and the last half. The first half with SHACAL-1 encryption algorithm 1 round does with 10 steps and composes of 4 round. The last half identically with SHACAL-1 decryption algorithm, has a structure. On the center inserts a symmetry layer, encryption and decryption algorithm identically, composes. In the experiments, the proposed SHACAL-1 algorithm showed similar execution time to that of the SHACAL-1. Thanks to the symmetric layer, the proposed algorithm makes it difficult for the attacks which take advantages of high probability path such as the linear cryptanalysis, differential cryptanalysis. The proposed algorithm can be applicable to the other block cipher algorithms which have different encryption and decryption and useful for designing a new block cipher algorithm.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.4
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• pp.860-868
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• 2011

Feistel and SPN are the two main structures in a block cipher. Feistel is a symmetric structure which has the same structure in encryption and decryption, but SPN is not a symmetric structure. In this paper, we propose a SPN block cipher so called SSB which has a symmetric structure in encryption and decryption. The proposed SSB is composed of the even numbers of N rounds. Each round consists of a round key addition layer, a subsitution layer, a byte exchange layer and a diffusion layer. The subsitution layer of the odd round is inverse function of one of the even round. And the diffusion layer is a MDS involution matrix. The differential and linear attack probability of SSB is $2^{-306}$ which is same with AES. The proposed symmetric SPN block cipher SSB is believed to construct a safe and efficient cipher in Smart Card and RFID environments which is in limited hardware and software resources.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.43 no.4 s.310
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• pp.80-87
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• 2006

Recently, the distribution and using of the digital multimedia contents are easy by developing the internet application program and related technology. However, the digital signal is easily duplicated and the duplicates have the same quality compare with original digital signal. To solve this problem, there is the multimedia fingerprint which is studied for the protection of copyright. Fingerprinting scheme is a techniques which supports copyright protection to track redistributors of electronic inform on using cryptographic techniques. Only regular user can know the inserted fingerprint data in fingerprinting schemes differ from a symmetric/asymmetric scheme and the scheme guarantee an anonymous before recontributed data. In this paper, we present a new scheme which is the detection of colluded multimedia fingerprint by neural network. This proposed scheme is consists of the anti-collusion code generation and the neural network for the error correction. Anti-collusion code based on BIBD(Balanced Incomplete Block Design) was made 100% collusion code detection rate about the average linear collusion attack, and the hopfield neural network using (n,k)code designing for the error bits correction confirmed that can correct error within 2bits.