• ETRI Journal
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• v.39 no.1
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• pp.108-115
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• 2017

ARIA is a 128-bit block cipher that has been selected as a Korean encryption standard. Similar to AES, it is robust against differential cryptanalysis and linear cryptanalysis. In this study, we analyze the security of ARIA against differential-linear cryptanalysis. We present five rounds of differential-linear distinguishers for ARIA, which can distinguish five rounds of ARIA from random permutations using only 284.8 chosen plaintexts. Moreover, we develop differential-linear attacks based on six rounds of ARIA-128 and seven rounds of ARIA-256. This is the first multidimensional differential-linear cryptanalysis of ARIA and it has lower data complexity than all previous results. This is a preliminary study and further research may obtain better results in the future.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.17 no.1
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• pp.121-125
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• 2007

Differential cryptanalysis and linear cryptanalysis are the most powerful approaches known for attacking many block ciphers and used to evaluating the security of many block ciphers. So designers have designed secure block ciphers against these cryptanalyses. In this paper, we present new three block cipher structures. And for given r, we prove that differential(linear) probabilities for r-round blockcipher structures are upper bounded by $p^2(q^2),\;2p^2(2q^2)$ if the maximum differential(linear) probability is p(q) and the round function is a bijective function.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.11 no.3
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• pp.45-52
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• 2001

In this paper, we examine the method for evaluating the security of SPN structures against differential cryptanalysis and linear cryptanalysis. We present an example of SPN structures in which there is a considerable difference between the differential probabilities and the characteristic probabilities. Then we 7pose an algorithm for estimating the maximum differential probabilities and the maximum linear hull probabilities of SPN structures and an useful method for accelerating the proposed algorithm. By using this method, we obain the maximum differential probabilities and the maximum linear probabilities of round function F of block cipher E2.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.28 no.6
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• pp.1379-1392
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• 2018

The complexity of the differential-linear cryptanalysis is strongly influenced by the probability of the differential-linear characteristic computed under the assumption of round independence, linear approximation independence, and uniformity for the trail that does not satisfy differential trail. Therefore, computing the exact probability of the differential-linear characteristic is a very important issue related to the validity of the attack. In this paper, we propose a new concept called DLCT(Differential-Linear Connectivity Table) for the differential-linear cryptanalysis. Additionally, we propose an improved probability computation technique of differential-linear characteristic by applying DLCT. By doing so, we were able to weaken linear approximation independence assumption. We reanalyzed the previous results by applying DLCT to DES and SERPENT. The probability of 7-round differential-linear characteristic of DES is $1/2+2^{-5.81}$, the probability of 9-round differential-linear characteristic of SERPENT is computed again to $1/2+2^{-57.9}$, and data complexity required for the attack is reduced by $2^{0.2}$ and $2^{2.2}$ times, respectively.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.9 no.3
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• pp.63-74
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• 1999

In this paper we present a Hangul Encryption Algorithm (HEA) which encrypts composition Hangul syllables into composition Hangul syllables using the non-linear structure of Hangul. Since ciphertexts generated by HEA are displayable characters HEA can be used in applications such as Privacy Enhanced mail (PEM) where ciphertexts should be displayable characters. HEA is based on DES and it can be shown that HEA is as safe as DES against the exhaustive key search differential cryptanalysis and linear cryptanalysis. HEA also has randomness of phonemes of ciphertexts and satisfies plaintext-ciphetext avalanche effect and key-ciphertext avalanche effect.

• Journal of the Korea Computer Industry Society
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• v.4 no.4
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• pp.523-532
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• 2003

In this paper, we designed a 128-bit block cipher, Lambda, which has 16-round extended 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 Lambda. Because of the strong diffusion effect of the algorithm, we could get a 8-round differential characteristic with probability $2^{-192}$ and a linear characteristic with probability $2^{-128}$. For the Lambda with 128-bit key, there is no shortcut attack, which is more efficient than the exhaustive key search, for more than 8 rounds of the algorithm.

• 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.

• ETRI Journal
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• v.23 no.4
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• pp.158-167
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• 2001

We examine the diffusion layers of some block ciphers referred to as substitution-permutation networks. We investigate the practical and provable security of these diffusion layers against differential and linear cryptanalysis. First, in terms of practical security, we show that the minimum number of differentially active S-boxes and that of linearly active S-boxes are generally not identical and propose some special conditions in which those are identical. We also study the optimal diffusion effect for some diffusion layers according to their constraints. Second, we obtain the results that the consecutive two rounds of SPN structure provide provable security against differential and linear cryptanalysis, i.e., we prove that the probability of each differential (resp. linear hull) of the consecutive two rounds of SPN structure with a maximal diffusion layer is bounded by $p^n(resp.q^n)$ and that of each differential (resp. linear hull) of the SDS function with a semi-maximal diffusion layer is bounded by $p^{n-1}(resp. q^{n-1})$, where p and q are maximum differential and linear probabilities of the substitution layer, respectively.

• 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.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.8 no.1
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• pp.65-70
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• 1998

K. Nyberg and L.R. Knudsen showed a prototype of a DES-like cipher$^{[1]}$ which has a provable security against differential cryptanalysis. But in the last year, at FSE'97 T. Jakobsen ane L.R.Knudsen broked it by using higher order differential attack and interpolation attack$^{[2]}$ . Furthermore the cipher was just a theoretically proposed one to demonstrate how to construct a cipher which is procably secure against differential cryptanalysis$^{[3]}$ and it was suspected to have a large complexity for its implementation.Inthis paper the two improved results for the dfficidnt hardware and software implementation.