• Journal of the Korea Institute of Information Security & Cryptology
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• v.19 no.2
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• pp.31-38
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• 2009

To provide the privacy of a keyword, a public key encryption with keyword search(PEKS) firstly was propsed by Boneh et al. The PEKS scheme enables that an email sender sends an encrypted email with receiver's public key to an email server and a server can obtain the relation between the given encrypted email and an encrypted query generated by a receiver. In this email system, we easily consider the situation that a user sends the one identical encrypted email to multi-receiver like as group e-mail. Hwang and Lee proposed a searchable public key encryption considering multi-receivers. To reduce the size of transmission data and the server's computation is important issue in multi-receiver setting. In this paper, we propose an efficient searchable public key encryption for multi-receiver (mPEKS) which is more efficient and reduces the server's pairing computation.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.1
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• pp.100-108
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• 2018

This paper describes a design of scalable RSA public-key cryptography processor supporting four key lengths of 512/1,024/2,048/3,072 bits. The modular multiplier that is a core arithmetic block for RSA crypto-system was designed with 32-bit datapath, which is based on the CIOS (Coarsely Integrated Operand Scanning) Montgomery modular multiplication algorithm. The modular exponentiation was implemented by using L-R binary exponentiation algorithm. The scalable RSA crypto-processor was verified by FPGA implementation using Virtex-5 device, and it takes 456,051/3,496347/26,011,947/88,112,770 clock cycles for RSA computation for the key lengths of 512/1,024/2,048/3,072 bits. The RSA crypto-processor synthesized with a $0.18{\mu}m$ CMOS cell library occupies 10,672 gate equivalent (GE) and a memory bank of $6{\times}3,072$ bits. The estimated maximum clock frequency is 147 MHz, and the RSA decryption takes 3.1/23.8/177/599.4 msec for key lengths of 512/1,024/2,048/3,072 bits.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.19 no.6
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• pp.17-22
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• 2009

Certificateless cryptography eliminates the need of certificacates in the public key crytosystems and solves the inherent key escrow problem in identity-based cryptosystems. This paper demonstrates that two certificateless signature schemes proposed by Guo et al. and Wang et al. respectively are insecure against key replacement attacks by a type I adversary. We show that the adversary who can replace a signer's public key can forge signatures under the replaced public key. We then make a suggestion to prevent the attacks.

• Journal of the Korea Society of Computer and Information
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• v.8 no.4
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• pp.104-110
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• 2003

In this paper, we proposed hybrid cryptosystem of Diffie-Hellman base in Elliptic Curve, and explained for specific protocol design. The proposed system is efficient hybrid cryptosystems system that offer implicit key authentication about sender and receiver unlike existing hybrid system. This system increased safety generating session key using pseudo-random number generator by cryptographic. Because the system is hybrid system, it is more efficient in calculation amount aspect supplementing merit and fault of public key system and secret key system. Also, the system can not get right plaintext except receiver even if sender's secret key is revealed and impersonation attack is impossible. And the system offers security on known keys without influencing in safety of other session's cryptogram even if session key is exposed. And the system is provided safety about mutual entity authentication and replay attack.

• Proceedings of the Korea Information Processing Society Conference
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• 2023.05a
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• pp.137-139
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• 2023

양자 컴퓨터가 현대 암호 시스템의 보안성을 위협하고 있음에 따라, 최근 잠재적인 양자 공격들에 대한 분석 연구들이 다수 발표되고 있다. 공개키 암호인 RSA와 ECC의 경우, Shor 알고리즘에 의해 다항시간 내에 해결됨으로써 보안성이 완전히 붕괴되는 반면, 대칭키 암호는 Grover 알고리즘에 의해 보안 강도가 제곱근으로 감소하기 때문에 키 길이를 증가시킴으로써 기존 보안성을 복구할 수 있다. 이론적으로 Grover 알고리즘은 보안성을 훼손시키지만, 현실적인 공격 난이도가 매우 높음에 따라 대상 암호에 대한 양자 회로 최적화 구현이 중요하다. 이에 본 논문에서는 블록암호 RC5를 양자 회로 상에서 최적화하고 이를 기반으로 Grover 공격 비용을 추정한다. 마지막으로, 추정한 비용을 NIST의 양자 후 보안 강도 평가와 함께 비교함으로써 RC5에 대한 양자 암호 분석을 수행한다.

• The Journal of the Korea institute of electronic communication sciences
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• v.17 no.2
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• pp.357-364
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• 2022

A pseudo-random number generator (PRNG) is a program used when a large amount of random numbers is needed. It is used to generate symmetric keys in symmetric key cryptography systems, generate public key pairs in public key cryptography or digital signatures, and generate columns used for padding with disposable pads. Cellular Automata (CA), which is useful for specific representing nonlinear dynamics in various scientific fields, is a discrete and abstract computational system that can be implemented in hardware and is applied as a PRNG that generates keys in cryptographic systems. In this paper, I propose an algorithm for synthesizing a programmable 5-neighbor CA based PRNG that can effectively generate a nonlinear sequence using 5-neighbor CA with the radius of the neighboring cell increased by 2.

• Journal of KIISE:Computer Systems and Theory
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• v.30 no.2
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• pp.93-98
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• 2003

This paper presents two new algorithms and their architectures for $AB^2 $ multiplication over $GF(2^m)$.First, a new architecture with a new algorithm is designed based on LFSR (Linear Feedback Shift Register) architecture. Furthermore, modified $AB^2 $ multiplier is derived from the multiplier. The multipliers and the structure use AOP (All One Polynomial) as a modulus, which hat the properties of ail coefficients with 1. Simulation results thews that proposed architecture has lower hardware complexity than previous architectures. They could be. Therefore it is useful for implementing the exponential ion architecture, which is the tore operation In public-key cryptosystems.

• The KIPS Transactions:PartC
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• v.9C no.2
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• pp.163-172
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• 2002

Java Card API porvide benifit for development program based on smart card using limmited resource. This APIs does not support arithmetic operations such as modular arithmetic, greatest common divisor calculation, and generation and certification of prime number, which is necessary arithmetic in PKI algorithm implementation. In this paper, we implement class BigInteger acted in the Java Card platform because that Java Card APIs does not support class BigInteger necessary in implementation of PKI algorithm.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.31 no.3
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• pp.473-480
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• 2021

To achieve the high-speed implementation of post-quantum cryptography, primitive operations should be tailored to the architecture of the target processor. In this paper, we present the optimized implementation of multiplier operation on RISC-V processor for post-quantum cryptography. Particularly, the column-wise multiplication algorithm is optimized with the primitive instruction of RISC-V processor, which improved the performance of 256-bit and 512-bit multiplication by 19% and 8% than previous works, respectively. Lastly, we suggest the instruction extension for the high-speed multiplication on the RISC-V processor.

• Review of KIISC
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• v.33 no.6
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• pp.37-43
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• 2023

현재 사용되고 있는 RSA, ECC 등 비대칭키 암호알고리즘은 앞으로 나올 양자컴퓨터와 양자알고리즘의 빠른 계산 속도로 알고리즘의 비가역성이 깨질 수 있음이 알려졌다. 이는 공개키로부터 비밀키를 계산할 수 있음을 의미한다. 이를 극복하기 위해 미국 국립표준기술연구소 (NIST)는 최근에 양자 내성 암호 (PQC) 알고리즘 선정과 표준화 작업을 진행해 왔으며, 4차 라운드에 진입해 있다. PQC 알고리즘에 필요한 PQC 비밀키는 PQC 알고리즘이 구현된 칩 외부에서 주입하거나 칩 내부에서 자체 생성을 하여 사용하는데, 이 비밀키를 비휘발성 메모리 (NVM) 등에 저장한다. 만약 시스템의 보안 취약성으로 인해 비밀키가 노출된다면 아무리 PQC 알고리즘이 강력해도 전체 시스템이 무너진다. 즉, 알고리즘의 수학적 능력과 무관하게 해당 보안 시스템은 무력화되는 것이다. 본 논문에서는 물리적 복제 방지 기능 (PUF)을 사용하여PQC 비밀키를 안전하게 보호하고, 이를 기반으로 전체 시스템을 보호할 것을 제안한다. PQC 비밀키가 외부에서 주입되면 해당키는 NVM에 저장되기 전에 PUF 키로 암호화 될 수 있다. PUF 값에서 파생되는 PUF 키는 필요할 때 마다 다시 만들어서 사용이 가능하므로 메모리에 저장할 필요가 없으며, 따라서 외부 공격에 PUF 키가 노출 되지 않는다. 반도체 수동소자로 이루어지는 Via PUF 기술은 최악의 환경 변화에도 그 특성이 유지되는 가장 최적의 PUF 기능을 제공한다.