• Journal of the Korea Institute of Information Security & Cryptology
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• v.9 no.3
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• pp.27-38
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• 1999

We study on the security for the block ciphers with 20block structure which have provable security against DC and LC on the view point of higher order DC, 2-block structures are classified three types according to the location of round function such as C(Center)-type R(Right)-type and L(Left)-type We prove that in the case of 4 rounds encryption function these three types provide the equal strength against higher order DC and that in the case of 5 or more rounds R-type is weaker than C-type and L-type.

• ETRI Journal
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• v.36 no.6
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• pp.1032-1040
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• 2014

The Lai-Massey scheme, proposed by Vaudenay, is a modified structure in the International Data Encryption Algorithm cipher. A family of block ciphers, named FOX, were built on the Lai-Massey scheme. Impossible differential cryptanalysis is a powerful technique used to recover the secret key of block ciphers. This paper studies the impossible differential cryptanalysis of the Lai-Massey scheme with affine orthomorphism for the first time. Firstly, we prove that there always exist 4-round impossible differentials of a Lai-Massey cipher having a bijective F-function. Such 4-round impossible differentials can be used to help find 4-round impossible differentials of FOX64 and FOX128. Moreover, we give some sufficient conditions to characterize the existence of 5-, 6-, and 7-round impossible differentials of Lai-Massey ciphers having a substitution-permutation (SP) F-function, and we observe that if Lai-Massey ciphers having an SP F-function use the same diffusion layer and orthomorphism as a FOX64, then there are indeed 5- and 6-round impossible differentials. These results indicate that both the diffusion layer and orthomorphism should be chosen carefully so as to make the Lai-Massey cipher secure against impossible differential cryptanalysis.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.18 no.3
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• pp.69-77
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• 2008

In the recent years, power attacks were widely investigated, and so various countermeasures have been proposed. In the case of block ciphers, masking methods that blind the intermediate results in the algorithm computations(encryption, decryption, and key-schedule) are well-known. Applications of masking methods are able to vary in different block ciphers, therefore suitable masking methods about each ciphers have been researched. Existed methods of ARIA have many revisions of mask value. And because existed masking methods pay no regard for key schedule, secret information can be exposed. In the case of ARIA, this problem is more serious than different block ciphers. Therefore we proposes an efficient masking scheme of ARIA including the key-schedule. Our method reduces time-complexity of ARIA encryption, and solve table-size problem of the general ARIA masking scheme from 256*8 byte to 256*6 byte.

• Journal of Advanced Information Technology and Convergence
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• v.9 no.2
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• pp.115-123
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• 2019

White-box cryptography is an implementation technique in order to protect secret keys of cryptographic algorithms in the white-box attack model, which is the setting that an adversary has full access to the implementation of the cryptographic algorithm and full control over their execution. This concept was introduced in 2002 by Chow et al., and since then, there have been many proposals for secure implementations. While there have been many approaches to construct a secure white-box implementation for the ciphers with SPN structures, there was no notable result about the white-box implementation for the block ciphers with Feistel structure after white-box DES implementation was broken. In this paper, we propose a secure white-box implementation for a block cipher SEED with Feistel structure, which can prevent the previous known attacks for white-box implementations. Our proposal is simple and practical: it is performed by only 3,376 table lookups during each execution and the total size of tables is 762.5 KB.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.17 no.1
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• pp.165-184
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• 2023

The ARX-based lightweight block cipher is widely used in resource-constrained IoT devices due to fast and simple operation of software and hardware platforms. However, there are three weaknesses to ARX-based lightweight block ciphers. Firstly, only half of the data can be changed in one round. Secondly, traditional ARX-based lightweight block ciphers are static structures, which provide limited security. Thirdly, it has poor diffusion when the initial plaintext and key are all 0 or all 1. This paper proposes a new dynamic ARX-based lightweight block cipher to overcome these weaknesses, called DABC. DABC can change all data in one round, which overcomes the first weakness. This paper combines the key and the generalized two-dimensional cat map to construct a dynamic permutation layer P1, which improves the uncertainty between different rounds of DABC. The non-linear component of the round function alternately uses NAND gate and AND gate to increase the complexity of the attack, which overcomes the third weakness. Meanwhile, this paper proposes the round-based architecture of DABC and conducted ASIC and FPGA implementation. The hardware results show that DABC has less hardware resource and high throughput. Finally, the safety evaluation results show that DABC has a good avalanche effect and security.

• Journal of IKEEE
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• v.22 no.1
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• pp.38-45
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• 2018

An integrated cryptographic processor that efficiently integrates ARIA, AES block ciphers and Whirlpool hash function into a single hardware architecture is described. Based on the algorithm characteristics of ARIA, AES, and Whirlpool, we optimized the design so that the hardware resources of the substitution layer and the diffusion layer were shared. The round block was designed to operate in a time-division manner for the round transformation and the round key expansion of the Whirlpool hash, resulting in a lightweight hardware implementation. The hardware operation of the integrated ARIA-AES-Whirlpool crypto-processor was verified by Virtex5 FPGA implementation, and it occupied 68,531 gate equivalents (GEs) with a 0.18um CMOS cell library. When operating at 80 MHz clock frequency, it was estimated that the throughputs of ARIA, AES block ciphers, and Whirlpool hash were 602~787 Mbps, 682~930 Mbps, and 512 Mbps, respectively.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.18 no.3
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• pp.23-32
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• 2008

The computing power of graphics processing units(GPU) has already surpassed that of CPU and the gap between their powers is getting wider. Thus, research on GPGPU which applies GPU to general purpose becomes popular and shows great success especially in the field of parallel data processing. Since the implementation of cryptographic algorithm using GPU was started by Cook et at. in 2005, improved results using graphic libraries such as OpenGL and DirectX have been published. In this paper, we present skills and results of implementing block ciphers using CUDA library announced by NVIDIA in 2007. Also, we discuss a general method converting source codes of block ciphers on CPU to those on GPU. On NVIDIA 8800GTX GPU, the resulting speeds of block cipher AES, ARIA, and DES are 4.5Gbps, 7.0Gbps, and 2.8Gbps, respectively which are faster than the those on CPU.

• Journal of Advanced Navigation Technology
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• v.13 no.6
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• pp.977-983
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• 2009

Recently, several DDP, DDO and COS-based block ciphers have been proposed for hardware implementations with low cost. However, most of them are vulnerable to related-keyt attacks. A 12-round block cipher SCOS-3 is desinged to eliminate the weakness of DDP, DDO and COS-based block ciphers. In this paper, we propose a related-key differential attack on an 11-round reduced SCOS-3. The attack on an 11-round reduced SCOS-3 requires $2^{58}$ related-key chosen plaintexts and $2^{117.54}$ 11-round reduced SCOS-3 encryptions. This work is the first known attack on SCOS-3. Therefore, SCOS-3 is still vulnerable to related-key attacks.

• Journal of information and communication convergence engineering
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• v.3 no.1
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• pp.5-8
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• 2005

Dynamic cipher has the property that the key-size, the number of round, and the plaintext-size are scalable simultaneously. We present the method for designing secure Dynamic cipher against meet-in-the-middle attack and linear cryptanalysis. Also, we show that the differential cryptanalysis to Dynamic cipher is hard. In this paper we propose a new network called Dynamic network for symmetric block ciphers.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.21 no.5
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• pp.15-25
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• 2011

A differential fault analysis(DFA) is one of the most important side channel attacks on block ciphers. Most block ciphers, such as DES, AES, ARIA, SEED and so on., have been analysed by this attack. In 2008, Wei et al. proposed the first DFA on ARIA-128. Their attack can recover the 128-bit secrey key by about 45 faulty ciphertexts. In this paper, we propose an improved DFA on ARIA-128. We can recover the 12S-bit secret key by only 4 faulty ciphertexts with the computational complexity of O($2^{32}$).