• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.11
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• pp.878-883
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• 2020

Cryptographic algorithms are used to prevent the illegal manipulation of data. They are divided into public-key cryptosystems and symmetric-key cryptosystems. Public-key cryptosystems require considerable time for encryption and decryption compared to symmetric-key cryptosystem. On the other hand, key management, and delivery are easier for public-key cryptosystems than symmetric-key cryptosystems because different keys are used for encryption and decryption. Furthermore, hash functions are being used very effectively to verify the integrity of the digital content, as they always generate output with a fixed size using the data of various sizes as input. This paper proposes a method using RSA public-key cryptography and a hash function to determine if a digital image is deformed or not and to detect the manipulated location. In the proposed method, the entire image is divided into several blocks, 64×64 in size. The watermark is then allocated to each block to verify the deformation of the data. When deformation occurs, the manipulated pixel will be divided into smaller 4×4 sub-blocks, and each block will have a watermark to detect the location. The safety of the proposed method depends on the security of the cryptographic algorithm and the hash function.

• Journal for History of Mathematics
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• v.11 no.2
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• pp.8-16
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• 1998

We survey the development of cryptography from the ancient to the present as a mathematical point of view, and recent results of public key cryptosystems.

• Proceedings of the Korea Multimedia Society Conference
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• 2003.11a
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• pp.158-161
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• 2003

1985년 N. Koblitz와 V. Miller가 각각 독립적으로 제안한 타원곡선 암호시스템(ECC : Elliptic Curve Cryptosystems)은 유한체 위에서 정의된 타원곡선 군에서의 이산대수 어려움에 기초한다. 타원곡선 암호시스템은 다른 공개키 시스템에 비해 보다 짧은 길이의 키만으로도 동일한 수준의 안전도를 유지할 수 있다는 장점으로 인하여, 스마트카드나 모바일 시스템 등에서와 같이 메모리와 처리능력이 제한된 하드웨어에도 이식 가능한 장점이 있다. 본 논문에서는 타원곡선 암호시스템에 필요한 유한체 연산을 이진체(Binary Finite Field)인 GF(2$^{193}$ )과 OEF(Oprimal Extension Field) 상에서 VHDL 언어를 사용하여 구현을 하였고 각 연산의 성능을 비교하였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.4
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• pp.2254-2275
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• 2017

In this paper, we present an IND-CCA2 secure certificateless proxy re-encryption scheme in the random oracle model. A certificateless public key cryptography simplifies the certificate management in a traditional public key infrastructure and the built-in key escrow feature in an identity-based public key cryptography. Our scheme shares the merits of certificateless public key encryption cryptosystems and proxy re-encryption cryptosystems. Our certificateless proxy re-encryption scheme has several practical and useful properties - namely, multi-use, unidirectionality, non-interactivity, non-transitivity and so on. The security of our scheme bases on the standard bilinear Diffie-Hellman and the decisional Bilinear Diffie-Hellman assumptions.

• ETRI Journal
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• v.29 no.5
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• pp.619-632
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• 2007

Side channel attacks are a very serious menace to embedded devices with cryptographic applications. To counteract such attacks many randomization techniques have been proposed. One efficient technique in elliptic curve cryptosystems randomizes addition chains with binary signed digit (BSD) representations of the secret key. However, when such countermeasures have been used alone, most of them have been broken by various simple power analysis attacks. In this paper, we consider combinations which can enhance the security of countermeasures using BSD representations by adding additional countermeasures. First, we propose several ways the improved countermeasures based on BSD representations can be attacked. In an actual statistical power analysis attack, the number of samples plays an important role. Therefore, we estimate the number of samples needed in the proposed attack.

• Smart Media Journal
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• v.6 no.2
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• pp.15-25
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• 2017

The security and privacy issues derived from unsecurely storing biometrics templates in biometric authentication/ recognition systems have opened a new research area about how to secure the stored biometric templates. Biometrics-based key generation is the newest approach that provides not only a mechanism to protect stored biometric templates in authentication/ recognition systems, but also a method to integrate biometric systems with cryptosystems. Therefore, this approach has attracted much attention from researchers worldwide. A review of current research state to summarize the achievements and remaining works is necessary for further works. In this study, we first outlined the requirements and the primary challenges when implementing these systems. We then summarize the proposed techniques and achievements in representative studies on biometrics-based key generation. From that, we give a discussion about the accomplishments and remaining works with the corresponding challenges in order to provide a direction for further researches in this area.

• Review of KIISC
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• v.7 no.4
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• pp.5-11
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• 1997

본 논문에서는 최근 주목받고 있는 타원 곡선을 이용한 암호 시스템에 대해 고찰해본다. 타원 곡선을 이용한 암호 시스템의 장점 및 이를 이용하여 구현한 여러가지 시스템에 대해 살펴보고, 또한 타원 곡선으로의 평문 imbedding 방법을 제시해 본다.

• Proceedings of the Optical Society of Korea Conference
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• 2008.02a
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• pp.417-418
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• 2008

• Journal of KIISE:Computer Systems and Theory
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• v.31 no.1_2
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• pp.51-58
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• 2004

Most of pubic-key cryptosystems are built on the basis of arithmetic operations defined over the finite field GF$GF(2^m)$ .The other operations of finite fields except addition can be computed by repeated multiplications. Therefore, it is very important to implement the multiplication operation efficiently in public-key cryptosystems. We propose an efficient bit-parallel normal basis multiplier for$GF(2^m)$ fields defined by All-One Polynomials. The gate count and time complexities of our proposed multiplier are lower than or equal to those of the previously proposed multipliers of the same class. Also, since the architecture of our multiplier is regular, it is suitable for VLSI implementation.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.2
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• pp.49-54
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• 2008

In cryptosystems based on finite fields, a modular multiplication operation is the most crucial part of finite field arithmetic. Also, in multipliers with resource constrained environments, bit-serial output structures are used in general. This paper proposes two efficient bit-serial output multipliers with the polynomial basis representation for irreducible trinomials. The proposed multipliers have lower time complexity compared to previous bit-serial output multipliers. One of two proposed multipliers requires the time delay of $(m+1){\cdot}MUL+(m+1){\cdot}ADD$ which is more efficient than so-called Interleaved Multiplier with the time delay of $m{\cdot}MUL+2m{\cdot}ADD$. Therefore, in elliptic curve cryptosystems and pairing based cryptosystems with small characteristics, the proposed multipliers can result in faster overall computation. For example, if the characteristic of the finite fields used in cryprosystems is small then the proposed multipliers are approximately two times faster than previous ones.