• The KIPS Transactions:PartD
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• v.13D no.3 s.106
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• pp.437-444
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• 2006

A chaos cipher system that focuses on the stream cipher system has a demerit that the longer the text is, the slower the speed of the encryption and description and the transmission and reception. On this study, we designed the cipher web mail system showing much better capabilities than the existing web mail system as the text is longer. In the embodiment of the cipher web mail system, we developed the key stream, the encryption and description of the text and the inside and outside mail viewer and so on. After the efficiency test, it was valued high in the respect of the speed of the encryption and description and the transmission and reception. And it made up for the defect of the stream cipher system. We expect that we can use it through the persistent applied study in the server system security, the file security, the security of the internet information, the protection of the e-commerce system information and other fields based on the cipher technique as the wide use cipher system that can replace the block cipher system.

• The KIPS Transactions:PartC
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• v.8C no.5
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• pp.585-596
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• 2001

In this paper, a new stream cipher algorithm based on the chaos theory is proposed and is applied to a Web security system. The Web security system is composed of three parts： certificate authority (CA), Web client, and Web server. The Web client and server system include a secure proxy client (SPC) and a secure management server (SMS), respectively, for data encryption and decryption between them. The certificate is implemented based on X.509 and the RSA public key algorithm is utilized for key creation and distribution to certify both the client and server. Once a connection is established between the client and server, outgoing and incoming data are encrypted and decrypted, respectively, using one of the three cipher algorithms： chaos, SEED, and DES. The proposed chaos algorithm outperforms the other two conventional algorithms in processing time and complexity. Thus, the developed Web security system can be widely used in electronic commerce (EC) and Internet banking.

• Journal of Information Processing Systems
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• v.11 no.2
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• pp.310-324
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• 2015

The stream cipher Salsa20 and its reduced versions are among the fastest stream ciphers available today. However, Salsa20/7 is broken and Salsa20/12 is not as safe as before. Therefore, Salsa20 must completely perform all of the four rounds of encryption to achieve a good diffusion in order to resist the known attacks. In this paper, a new variant of Salsa20 that uses the chaos theory and that can achieve diffusion faster than the original Salsa20 is presented. The method has been tested and benchmarked with the original Salsa20 with a series of tests. Most of the tests show that the proposed chaotic Salsa of two rounds is faster than the original four rounds of Salsa20/4, but it offers the same diffusion level.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.14 no.4
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• pp.183-194
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• 2004

The proliferation of the Internet and the rapid progress of wire/wireless communication technology makes security of digital images more and more important since the exchanges of digital images occur more and more frequently. And as the tight relationship between chaos theory and cryptography, many researches for development of new encryption systems based on chaotic maps have been widely progressed recently. In this paper, we propose a digital image encryption system based on both one-dimensional PLCM(Piecewise Linear Chaotic Map) and two-dimensional baker map. This proposed system is a product cipher that contains a perturbance-based chaotic stream cipher based on ID PLCM and a chaotic block cipher based on 2D baker map and is very high secure and easily implementable cipher having both a good confusion property and a good diffusion property. And with test results, we showed this system is very secure against statistical attacks.

• Journal of the Korea Society of Computer and Information
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• v.13 no.5
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• pp.155-162
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• 2008

The security of digital image has become increasingly important with the development of the computing performance and internet. Therefore, the encryption algorithms exploiting chaos signal have recently attracted considerable attentions as a new method of image-encryption techniques. In this Paper, it is demonstrated that two different chaotic systems are synchronized by the methods of noise-induced synchronization. Based on this synchronization method, an image-encryption system is implemented and an image of Seok-Ga-Tap is encrypted as a verification of the performance of our system. The method suggested in this paper in which the noise is used as the key of decryption is superior to the existing methods in the aspect of the degree of encryption. In this paper, we Propose that the method is a new effective encryption algorithm as well as an easily applicable one.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.49 no.1
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• pp.29-38
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• 2012

Due to the rapid development of network environment and wireless communication technology, the distribution of digital video has made easily and the importance of the protection for digital video has been increased. This paper proposes the digital video encryption system based on multiple chaos maps for MPEG-2 video encoding process. The proposed method generates secret hash key of having 128-bit characteristics from hash chain using Tent map as a basic block and generates $8{\times}8$ lattice cipher by applying this hash key to Logistic map and Henon map. The method can reduce the encryption overhead by doing selective XOR operations between $8{\times}8$ lattice cipher and some coefficient of low frequency in DCT block and it provides simple and randomness characteristic because it uses the architecture of combining chaos maps. Experimental results show that PSNR of the proposed method is less than or equal to 12 dB with respect to encrypted video, the time change ratio, compression ratio of the proposed method are 2%, 0.4%, respectively so that it provides good performance in visual security and can be applied in real time.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.9
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• pp.4487-4511
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• 2018

A fast image encryption system based on substitution and diffusion was proposed, which includes one covering process, one substitution process and two diffusion processes. At first, Chen's chaotic system together with an external 256-bit long secret key was used to generate the key streams for image encryption, in which the initial values of Chen's chaotic system were regarded as the public key. Then the plain image was masked by the covering process. After that the resulting image was substituted with the disturbed S-Box of AES. Finally, the substituted image was diffused twice with the add-modulo operations as the core to obtain the cipher image. Simulation analysis and comparison results with AES and some existing image cryptosystems show that the proposed image cryptosystem possesses the merits of fast encryption/decryption speed, good statistical characteristics, strong sensitivity and etc., and can be used as a candidate system of network security communication.