• Journal of the Korea Institute of Information Security & Cryptology
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• v.12 no.6
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• pp.71-80
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• 2002

To provide the confidentiality of messages transmitted over the network, the use of cryptographic system is increasing gradually and the hybrid cryptosystem, which combines the advantages of the symmetric cryptosystem and the public key cryptosystem is widely used. In this paper, we proposes a new hybrid cryptosystem capable of providing implicit authentication for the sender of the ciphertext by means of the 1-pass key distribution protocol that offers implicit key authentication, hash function and symmetric cryptosystem. Also, we describe some examples such as the Diffie-Hellman based system and the Nyberg-Ruppel based system. The proposed hybrid cryptosystem is an efficient more than general public key cryptosystems in the aspect of computation work and provides implicit authentication for the sender without additional increase of the communication overhead.

• 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 Society of Industrial Information Systems
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• v.10 no.3
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• pp.57-63
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• 2005

Kim and Fenn et al. proposed two modular AB multipliers based on LFSR(Linear Feedback Shift Register) architecture. These multipliers use AOP, which has all coefficients with '1', as an irreducible polynomial. Thereby, they have good hardware complexity compared to the previous architectures. This paper proposes a modular $AB^2$ multiplier based on LFSR architecture and a modular exponentiation architecture to improve the hardware complexity of the Kim's. Our multiplier also use the AOP as an irreducible polynomial as the Kim architecture. Simulation result shows that our multiplier reduces the hardware complexity about $50\%$ in the perspective of XOR and AND gates compared to the Kim's. The architecture could be used as a basic block to implement public-key cryptosystems.

• 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.

• Convergence Security Journal
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• v.24 no.2
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• pp.71-78
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• 2024

As the rapid development of quantum computing compromises current public key encryption methods, the National Institute of Standards and Technology (NIST) in the United States has initiated the Post-Quantum Cryptography(PQC) project to develop new encryption standards that can withstand quantum computer attacks. This project involves reviewing and evaluating various cryptographic algorithms proposed by researchers worldwide. The initially selected quantum-resistant cryptographic algorithms were developed based on lattices and hash functions. Currently, algorithms offering diverse technical approaches, such as BIKE, Classic McEliece, and HQC, are under review in the fourth round. CRYSTALS-KYBER, CRYSTALS-Dilithium, FALCON, and SPHINCS+ were selected for standardization in the third round. In 2024, a final decision will be made regarding the algorithms selected in the fourth round and those currently under evaluation. Strengthening the security of public key cryptosystems in preparation for the quantum computing era is a crucial step expected to have a significant impact on protecting future digital communication systems from threats. This paper analyzes the security and efficiency of quantum-resistant cryptographic algorithms, presenting trends in this field.

• 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.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.15 no.3
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• pp.77-89
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• 2005

As the ID-based public key cryptosystems become a very active research area, a number of ID-based key agreement protocols have been proposed, but unfortunately many of them were analyzed that there were some security flaws in the protocols. In addition to key agreement protocols, in recent, Liu et al. and Kim et al. proposed the key agreement protocols that multiple session keys are established at once among participated entities. In this paper, we propose an ID-based tripartite key agreement protocol that establishes 8 keys by improving the efficiency of the Liu et al's. Moreover, the proposed protocol can be used in the situation where multiple different private key generators(PKG) are involved. Therefore, because the private key issued by different PKGs belonging to each entity's domain can be used, our proposed scheme is more efficiently applicable to the practical applications.

• Journal of Korea Society of Industrial Information Systems
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• v.8 no.3
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• pp.85-90
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• 2003

This paper proposes a modular multiplier based on LFSR (Linear Feedback Shift Register) architecture with efficient area complexity over GF(2/sup m/). At first, we examine the modular exponentiation algorithm and propose it's architecture, which is basic module for public-key cryptosystems. Furthermore, this paper proposes on efficient modular multiplier as a basic architecture for the modular exponentiation. The multiplier uses AOP (All One Polynomial) as an irreducible polynomial, which has the properties of all coefficients with '1 ' and has a more efficient hardware complexity compared to existing architectures.

• ETRI Journal
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• v.25 no.5
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• pp.315-320
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• 2003

Elliptic curve cryptography (ECC) offers the highest security per bit among the known public key cryptosystems. The operation of ECC is based on the arithmetic of the finite field. This paper presents the design of a 193-bit finite field multiplier and an inversion unit based on a normal basis representation in which the inversion and the square operation units are easy to implement. This scalable multiplier can be constructed in a variable structure depending on the performance area trade-off. We implement it using Verilog HDL and a 0.35 ${\mu}m$ CMOS cell library and verify the operation by simulation.

• Proceedings of the Korea Information Processing Society Conference
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• 2002.11b
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• pp.1083-1086
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• 2002

1999년에 Paillier는 합성수 잉여류(composite residuosity class)에 기반을 둔 공개키 암호 방식을 제안하였다. 이는 고차 잉여를 결정하는 것이 계산상 어렵다는 가정 아래 제안된 새로운 확률 암호 방식이다. 현재, 이 새로운 공개키 암호 방식에 대한 안전성 및 변형된 Paillier 암호 방식들에 대한 연구가 다양한 방향에서 진행되고 있다. 요즘, 암호 알고리즘 연구에서 가장 활발하게 연구되고 있는 Paillier 암호 방식에 대하여 그 내용과 안전성에 대하여 수학적으로 자세히 분석하고, 개선된 Paillier 방식의 안전성과 선택적 암호문 공격에 대하여 분석하였나. 이후, Paillier 방식과 개선된 Paillier 방식의 효율성 및 안전성을 비교한다.