• Journal of the Korea Computer Industry Society
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• v.5 no.3
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• pp.405-414
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• 2004

In this paper, we designed a 128-bits block cipher, Circle-g, which has 18-rounds modified Feistel structure and analyzed its secureness by the differential cryptanalysis and linear cryptanalysis. We could have full diffusion effect from the two rounds of the Circle-g. Because of the strong diffusion effect of the F-function of the algorithm, we could get a 9-rounds DC characteristic with probability 2^{-144} and a 12-rounds LC characteristic with probability 2^{-144}. For the Circle-g with 128-bit key, there is no shortcut attack, which is more efficient than the exhaustive key search, for more than 12 rounds of the algorithm.

• The Journal of Society for e-Business Studies
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• v.5 no.1
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• pp.55-73
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• 2000

Recently; EC(Electronic Commerce) is increasing with high speed based on the expansion of Internet. EC which is done on the cyber space through Internet has strong point like independence from time and space. On the contrary, it also has weak point like security problem because anybody can access easily to the system due to open network attribute of Internet. Therefore, we need the solutions that protect the security problem for safe and useful EC activity. One of these solutions is the implementation of strong cipher algorithm. NC(Nonpolynomial Complete) cipher algorithm proposed in this paper is good for the security and it overcome the limit of current 64bits cipher algorithm using 128bits key length for input, output and encryption key, Moreover, it is designed for the increase of calculation complexity and probability calculation by adapting more complex design for subkey generation regarded as one of important element effected to encryption. The result of simulation by the comparison with other cipher algorithm for capacity evaluation of proposed NC cipher algorithm is that the speed of encryption and decryption is 7.63 Mbps per block and the speed of subkey generation is 2,42 μ sec per block. So, prosed NC cipher algorithm is regarded as proper level for encryption. Furthermore, speed of subkey generation shows that NC cipher algorithm has the probability used to MAC(Message Authentication Code) and block implementation of Hash function.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.24 no.4
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• pp.753-763
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• 2014

Recently financial institutions and large retailers have a large amount of personal information leakage accident occurred one after another, and the damage is a trend of increasing day by day. Regulation such as enforcing the encryption of the personal identification information are strengthened. Efficient technology to encrypt personal information is Format-preserving encryption. Typical encryption expand output data length than input data length and change a format. Format Preserving Encryption is an efficient method to minimize database and application modification, because it makes preserve length and format of input data. In this paper, to encrypt personal information efficiently, we propose newly Format Preserving Encryption using Block cipher mode of operation.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.12 no.5
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• pp.3-14
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• 2002

Rijndael-like structure is the special case of SPN structure. The linear transformation of Rijndael-like structure consisits of linear transformations of two types, the one is byte permutation $\pi$ and the other is linear tranformation $\theta$＝ ($\theta_1, \theta_2, \theta_3, \theta_4$), where each of $\theta_i$ separately operates on each of the four rows of a state. The block cipher, Rijndael is an example of Rijndael-like structures. In this paper. we present a new method for upper bounding the maximum differential probability and the maximum linear hull probability for Rijndael-like structures.

• KNOM Review
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• v.22 no.1
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• pp.68-76
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• 2019

Bitcoin, based on the blockchain technology is an online crypto-currency developed by Satoshi Nagamoto. Bitcoin, which was first issued on January 3, 2009, is rapidly evolving with increasing number of transactions. However, untoward incidents are occurring due to an increase in the number of Bitcoin transactions. Predicting the number of Bitcoin transactions is important to prepare for any issues that can occur in the Bitcoin network. This paper proposes to design model for predicting the number of Bitcoin transactions by applying two machine learning algorithms and then a model for predicting the number of Bitcoin transactions through experiments.

• Journal of IKEEE
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• v.19 no.3
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• pp.424-430
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• 2015

This paper proposes an optical cryptography application to 2-D page-oriented data based on CFB(Cipher Feedback) mode algorithm. The proposed method uses a free-space optical interconnected dual-encoding technique which performs XOR logic operations in order to implement 2-D page-oriented data encryption. The proposed method provides more enhanced cryptosystem with greater security strength than the conventional CFB block mode with 1-D encryption key due to the huge encryption key with 2-D arrayed page type. To verify the proposed method, encryption and decryption of 2-D page data and error analysis are carried out by computer simulations. The results show that the proposed CFB optical encryption system makes it possible to implement stronger cryptosystem with massive data processing and long encryption key compared to 1-D block method.

• Journal of Convergence for Information Technology
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• v.11 no.11
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• pp.66-74
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• 2021

With the development of the Internet, user authentication technology that proves me online is improving. Existing ID methods pose a threat of personal information leakage if the service provider manages personal information and security is weak, and the information subject is to the service provider. In this study, as online identification technology develops, we propose a DID-based self-authentication model to prevent the threat of leakage of personal information from a centralized format and strengthen sovereignty. The proposed model allows users to directly manage personal information and strengthen their sovereignty over information topics through VC issued by the issuing agency. As a research method, a self-authentication model that guarantees security and integrity is presented using a decentralized identifier method based on distributed ledger technology, and the security of the attack method is analyzed. Because it authenticates through DID Auth using public key encryption algorithms, it is safe from sniffing, man in the middle attack, and the proposed model can replace real identity card.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.16 no.5
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• pp.67-77
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• 2006

Radio Frequency IDentification (RFID) will soon become an important technology in various industries. Therefore, security mechanisms for Rm systems are emerging crucial problems in RFID systems. In order to guarantee privacy and security, it is desirable to encrypt the transferred data with a strong crypto algorithm. In this paper, we present the ultra-light weight Advanced Encryption Standard (AES) processor which is suitable for RFID tags. The AES processor requires only 3,992 logic gates and is capable of both 128-bit encryption and decryption. The processor takes 446 clock cycles for encryption of a 128-bit data and 607 clock cycles for decryption. Therefore, it shows 55% improved result in encryption and 40% in decryption from previous cases.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.20 no.6
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• pp.3-13
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• 2010

Differential Fault Analysis (DFA) is widely known for one of the most efficient method analyzing block cipher. In this paper, we propose a new type of DFA on DES (Data Encryption Standard). DFA on DES was first introduced by Biham and Shamir, then Rivain recently introduced DFA on DES middle rounds (9-12 round). However previous attacks on DES can only be applied to the encryption process. Meanwhile, we first propose the DFA on DES key-schedule. In this paper, we proposed a more efficient DFA on DES key schedule with random fault. The proposed DFA method retrieves the key using a more practical fault model and requires fewer faults than the previous DFA on DES.