• Journal of the Korea Institute of Information Security & Cryptology
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• v.9 no.1
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• pp.135-146
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• 1999

Most public key cryptosystems are constructed based on a modular exponentiation, which is further decomposed into a series of modular multiplications. We design a new systolic array multiplier to speed up modular multiplication using Montgomery algorithm. This multiplier with simple circuit for each processing element will save about 14% logic gates of hardware and 20% execution time compared with previous one.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.12 no.4
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• pp.99-114
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• 2002

Improved algorithms for elliptic scalar multiplication secure against side-channel attacks, such as timing and power analysis, are presented and analyzed. We first point out some potential security flaws often overlooked in most previous algorithms and then present a simple $\pm$1-signed encoding scheme that can be used to enhance the security and performance of existing algorithms. More specifically, we propose concrete signed binary and window algorithms based on the proposed $\pm$ 1-signed encoding and analyze their security and performance. The proposed algorithms are shown to be more robust and efficient than previous algorithms.

• International Journal of Computer Science & Network Security
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• v.21 no.4
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• pp.289-300
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• 2021

Non-abelian group based Cryptography is a field which has become a latest trend in research due to increasing vulnerabilities associated with the abelian group based cryptosystems which are in use at present and the interesting algebraic properties associated that can be thought to provide higher security. When developing cryptographic primitives based on non-abelian groups, the researchers have tried to extend the similar layouts associated with the traditional underlying mathematical problems and assumptions by almost mimicking their operations which is fascinating even to observe. This survey contributes in highlighting the different analogous extensions of traditional assumptions presented by various authors and a set of open problems. Further, suggestions to apply the Hamiltonian Cycle/Path Problem in a similar direction is presented.

• Proceedings of the Korea Information Processing Society Conference
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• 2009.04a
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• pp.1515-1518
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• 2009

최적정규기저(Optimal Normal Basis)를 이용한 $GF(2^m)$상의 곱셈은 ECC(Elliptic Curve Cryptosystems: 타원곡선 암호시스템) 및 유한체 산술 연산의 하드웨어 구현에 적합하다는 것은 잘 알려져 있다. 본 논문에서는 최적정규기저의 하드웨어적 장점을 이용하여 합성체(Composit Field)상의 곱셈기를 제안하며, 기존에 제안된 합성체상의 곱셈기와 비교 및 분석한다. 제안된 곱셈기는 최적정규기저 타입 I, II의 대칭성과 가수의 중복성을 이용한 열벡터의 재배열에 따른 XOR 연산의 재사용으로 낮은 하드웨어 복잡도와 작은 지연시간을 가진다.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.28 no.5
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• pp.1099-1112
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• 2018

The field of post-quantum cryptography (PQC) is an active area of research as cryptographers look for public-key cryptosystems that can resist quantum adversaries. Among those categories in PQC, code-based cryptosystem provides high security along with efficiency. Recent works on code-based cryptosystems focus on the side-channel resistant implementation since previous works have indicated the possible side-channel vulnerabilities on existing algorithms. In this paper, we recovered the secret key in HyMES(Hybrid McEliece Scheme) using a single power consumption trace. HyMES is a variant of McEliece cryptosystem that provides smaller keys and faster encryption and decryption speed. During the decryption, the algorithm computes the parity-check matrix which is required when computing the syndrome. We analyzed HyMES using the fact that the joint distributions of nonlinear functions used in this process depend on the secret key. To the best of our knowledge, we were the first to propose the side-channel analysis based on joint distributions of leakages on public-key cryptosystem.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.19 no.2
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• pp.11-21
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• 2009

The NTRU cryptosystem proposed by Hoffstein et al. in 1990s is a public key cryptosystem based on hard lattice problems. NTRU has many advantages compared to other public key cryptosystems such as RSA and elliptic curve cryptosystems. For example, it guarantees high speed encryption and decryption with the same level of security, and there is no known quantum computing algorithm for speeding up attacks against NTRD. In this paper, we analyze the security of NTRU against the simple power analysis (SPA) attack and the statistical power analysis (STPA) attack such as the correlation power analysis (CPA) attack First, we implement NTRU operations using NesC on a Telos mote, and we show how to apply CPA to recover a private key from collected power traces. We also suggest countermeasures against these attacks. In order to prevent SPA, we propose to use a nonzero value to initialize the array which will store the result of a convolution operation. On the other hand, in order to prevent STPA, we propose two techniques to randomize power traces related to the same input. The first one is random ordering of the computation sequences in a convolution operation and the other is data randomization in convolution operation.

• The Transactions of the Korea Information Processing Society
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• v.2 no.4
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• pp.611-618
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• 1995

In the high information societies, the requirement of encryption security is increasing so as to protect information from the threat of attacks by illegal changes of data, illegal leakage of data, disorder of data sequences and the unauthorized sender and an unauthorized receiver etc. In this paper, multivariable knapsack crytosystem is proposed for security of computer communication. This system is securer and simpler than the conventional knapsack cryptosystems. And, proposed cryptosystem composed what represented each element of superincreasing vector with multivar able polynomial after transforming it of ciphervector. For the deciphering of ciphertext, the plaintext is determined by using the integers of secret and the superincreasing vector of secret key. Thus, the stability of this cryptosystem is based on the difficulty of obtaining the root that ciphervector becomes the superincreasing vector, in substituting the integers of secret for ciphervector to represent with the miltivariable polynomial. The propriety of proposed multivariable knapsack cryptosystem was proved through computer simulation.

• ETRI Journal
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• v.42 no.4
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• pp.619-632
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• 2020

Highly dispersive S-boxes are desirable in cryptosystems as nonlinear confusion sublayers for resisting modern attacks. For a near optimal cryptosystem resistant to modern cryptanalysis, a highly nonlinear and low differential probability (DP) value is required. We propose a method based on a piecewise linear chaotic map (PWLCM) with optimization conditions. Thus, the linear propagation of information in a cryptosystem appearing as a high DP during differential cryptanalysis of an S-box is minimized. While mapping from the chaotic trajectory to integer domain, a randomness test is performed that justifies the nonlinear behavior of the highly dispersive and nonlinear chaotic S-box. The proposed scheme is vetted using well-established cryptographic performance criteria. The proposed S-box meets the cryptographic performance criteria and further minimizes the differential propagation justified by the low DP value. The suitability of the proposed S-box is also tested using an image encryption algorithm. Results show that the proposed S-box as a confusion component entails a high level of security and improves resistance against all known attacks.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.5
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• pp.1328-1342
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• 2013

Searchable encryption is a cryptographic protocol for searching a document in encrypted databases. A simple searchable encryption protocol, which is capable of using only one keyword at one time, is very limited and cannot satisfy demands of various applications. Thus, designing a searchable encryption with useful additional functions, for example, conjunctive keyword search, is one of the most important goals. There have been many attempts to construct a searchable encryption with conjunctive keyword search. However, most of the previously proposed protocols are based on public-key cryptosystems which require a large amount of computational cost. Moreover, the amount of computation in search procedure depends on the number of documents stored in the database. These previously proposed protocols are not suitable for extremely large data sets. In this paper, we propose a new searchable encryption protocol with a conjunctive keyword search based on a linked tree structure instead of public-key based techniques. The protocol requires a remarkably small computational cost, particularly when applied to extremely large databases. Actually, the amount of computation in search procedure depends on the number of documents matched to the query, instead of the size of the entire database.

• Journal of Korea Multimedia Society
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• v.20 no.8
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• pp.1321-1329
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• 2017

A quantum computer, based on quantum mechanics, is a paradigm of information processing that can show remarkable possibilities of exponentially improved information processing. This paradigm can be solved in a short time by calculating factoring problem and discrete logarithm problem that are typically used in public key cryptosystems such as RSA(Rivest-Shamir-Adleman) and ECC(Elliptic Curve Cryptography). In 2013, Lei et al. proposed a secure NTRU-based key distribution protocol for quantum computing. However, Lei et al. protocol was vulnerable to man-in-the-middle attacks. In this paper, we propose a NTRU(N-the truncated polynomial ring) key distribution protocol with mutual authentication only using NTRU convolution multiplication operation in order to maintain the security for quantum computing. The proposed protocol is resistant to quantum computing attacks. It is also provided a secure key distribution from various attacks such as man-in-the middle attack and replay attack.