• Current Optics and Photonics
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• v.5 no.2
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• pp.155-163
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• 2021

We propose a novel optical encryption scheme for cipher-feedback-block (CFB) mode, capable of encrypting two-dimensional (2D) page data with the use of two-step phase-shifting digital interferometry utilizing orthogonal polarization, in which the CFB algorithm is modified into an optical method to enhance security. The encryption is performed in the Fourier domain to record interferograms on charge-coupled devices (CCD)s with 256 quantized gray levels. A page of plaintext is encrypted into digital interferograms of ciphertexts, which are transmitted over a digital information network and then can be decrypted by digital computation according to the given CFB algorithm. The encryption key used in the decryption procedure and the plaintext are reconstructed by dual phase-shifting interferometry, providing high security in the cryptosystem. Also, each plaintext is sequentially encrypted using different encryption keys. The random-phase mask attached to the plaintext provides resistance against possible attacks. The feasibility and reliability of the proposed CFB method are verified and analyzed with numerical simulations.

• Journal of Advanced Information Technology and Convergence
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• v.9 no.2
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• pp.115-123
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• 2019

White-box cryptography is an implementation technique in order to protect secret keys of cryptographic algorithms in the white-box attack model, which is the setting that an adversary has full access to the implementation of the cryptographic algorithm and full control over their execution. This concept was introduced in 2002 by Chow et al., and since then, there have been many proposals for secure implementations. While there have been many approaches to construct a secure white-box implementation for the ciphers with SPN structures, there was no notable result about the white-box implementation for the block ciphers with Feistel structure after white-box DES implementation was broken. In this paper, we propose a secure white-box implementation for a block cipher SEED with Feistel structure, which can prevent the previous known attacks for white-box implementations. Our proposal is simple and practical: it is performed by only 3,376 table lookups during each execution and the total size of tables is 762.5 KB.

• KIPS Transactions on Computer and Communication Systems
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• v.10 no.4
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• pp.101-106
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• 2021

Quantum algorithms and quantum computers can break the security of many of the ciphers we currently use. If Grover's algorithm is applied to a symmetric key cipher with n-bit security level, the security level can be lowered to (n/2)-bit. In order to apply Grover's algorithm, it is most important to optimize the target cipher as a quantum circuit because the symmetric key cipher must be implemented as a quantum circuit in the oracle function. Accordingly, researches on implementing AES(Advanced Encryption Standard) or lightweight block ciphers as quantum circuits have been actively conducted in recent years. In this paper, korean lightweight block cipher LEA was optimized and implemented as a quantum circuit. Compared to the previous LEA quantum circuit implementation, quantum gates were used more, but qubits were drastically reduced, and performance evaluation was performed for this tradeoff problem. Finally, we evaluated quantum resources for applying Grover's algorithm to the proposed LEA implementation.

• Journal of the Korea Society of Computer and Information
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• v.15 no.2
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• pp.199-206
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• 2010

Society of digital information becomes gradually advancement, and it is a situation offered various service, but it is exposed to a serious security threat by a fast development of communication such as the internet and a network. There is required a research of technical encryption to protect more safely important information. And we require research for application of security technology in environment or a field to be based on a characteristics of market of an information security. The symmetric key cipher algorithm has same encryption key and decryption key. It is categorized to Block and Stream cipher algorithm according to conversion ways. This study inspects safety and reliability of proposed SEED, Stream cipher algorithm. And it confirms possibility of application on the communication environments. This can contribute to transact information safely by application of suitable cipher algorithm along various communication environmental conditions.

• JSTS:Journal of Semiconductor Technology and Science
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• v.4 no.4
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• pp.307-311
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• 2004

This paper presents an efficient architecture that optimizes the design of SEED S-box using composite field arithmetic. SEED is the Korean standard 128-bit block cipher algorithm developed by Korea Information Security Agency. The nonlinear function S-box is the most costly operation in terms. of size and power consumption, taking up more than 30% of the entire SEED circuit. Therefore the S-box design can become a crucial factor when implemented in systems where resources are limited such as smart cards. In this paper, we transform elements in $GF(2^8)$ to composite field $GF(((2^2)^2)^2)$ where more efficient computations can be implemented and transform the computed result back to $GF(2^8)$. This technique reduces the S-box portion to 15% and the entire SEED algorithm can be implemented at 8,700 gates using Samsung smart card CMOS technology.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2018.05a
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• pp.339-340
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• 2018

본 논문에서는 경량 블록암호 알고리듬 TWINE의 하드웨어 설계에 대해 기술한다. TWINE은 80-비트 또는 128-비트의 마스터키를 사용하여 64-비트의 평문(암호문)을 암호(복호)하여 64-비트의 암호문(평문)을 만드는 대칭키 블록암호이며, s-box와 XOR만 사용하므로 경량 하드웨어 구현에 적합하다는 특징을 갖는다. 암호화 연산과 복호화 연산의 하드웨어 공유를 통해 게이트 수가 최소화 되도록 구현하였으며, 설계된 TWINE 크립토 코어는 RTL 시뮬레이션을 통해 기능을 검증하였다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.4
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• pp.786-792
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• 2016

Camellia was jointly developed by Nippon Telegraph and Telephone Corporation and Mitsubishi Electric Corporation in 2000. Camellia specifies the 128-bit message block size and 128-, 192-, and 256-bit key sizes. In this paper, a modified round operation block which unifies a register setting for key schedule and a conventional round operation block is proposed. 16 ROMs needed for key generation and round operation are implemented using only 4 dual-port ROMs. Due to the use of a message buffer, encryption/decryption can be executed without a waiting time immediately after KA and KB are calculated. The suggested block cipher Camellia algorithm is designed using Verilog-HDL, implemented on Virtex4 device and operates at 184.898MHz. The designed cryptographic core has a maximum throughput of 1.183Gbps in 128-bit key mode and that of 876.5Mbps in 192 and 256-bit key modes. The cryptographic core of this paper is applicable to security module of the areas such as smart card, internet banking, e-commerce and satellite broadcasting.

• Journal of IKEEE
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• v.24 no.2
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• pp.468-474
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• 2020

This paper describes the hardware implementation of SPECK, a lightweight block cipher algorithm developed for the security of applications with limited resources such as IoT and wireless sensor networks. The block cipher SPECK crypto-core supports 8 block/key sizes, and the internal data-path was designed with 16-bit for small gate counts. The final round key to be used for decryption is pre-generated through the key initialization process and stored with the initial key, enabling the encryption/decryption for consecutive blocks. It was also designed to process round operations and key scheduling independently to increase throughput. The hardware operation of the SPECK crypto-core was validated through FPGA verification, and it was implemented with 1,503 slices on the Virtex-5 FPGA device, and the maximum operating frequency was estimated to be 98 MHz. When it was synthesized with a 180 nm process, the maximum operating frequency was estimated to be 163 MHz, and the estimated throughput was in the range of 154 ~ 238 Mbps depending on the block/key sizes.

• Journal of Korea Society of Industrial Information Systems
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• v.15 no.2
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• pp.1-9
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• 2010

Feistel and SPN are the two main structures in a block cipher. Feistel is a symmetric structure which has the same structure in encryption and decryption, but SPN is not a symmetric structure. In this paper, we propose a SPN which has a symmetric structure in encryption and decryption. The whole operations of proposed algorithm are composed of the even numbers of N rounds where the first half of them, 1 to N/2 round, applies a right function and the last half of them, (N+1)/2 to N round, employs an inverse function. And a symmetry layer is located in between the right function layer and the inverse function layer. In this paper, AES encryption and decryption function are selected for the right function and the inverse function, respectively. The symmetric layer is composed with simple matrix and round key addition. Due to the simplicity of the symmetric SPN structure in hardware implementation, the proposed modified AES is believed to construct a safe and efficient cipher in Smart Card and RFID environments where electronic chips are built in.

• Convergence Security Journal
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• v.18 no.4
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• pp.27-33
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• 2018

Stream cipher is an one-time-pad type encryption algorithm that encrypt plaintext using simple operation such as XOR with random stream of bits (or characters) as symmetric key and its security depends on the randomness of used stream. Therefore we can design more secure stream cipher algorithm by using mathematical analysis of the stream such as period, linear complexity, non-linearity, correlation-immunity, etc. The key stream in stream cipher is generated in linear feedback shift register(LFSR) having characteristic polynomial. The primitive polynomial is the characteristic polynomial which has the best security property. It is used widely not only in stream cipher but also in SEED, a block cipher using 8-degree primitive polynomial, and in Chor-Rivest(CR) cipher, a public-key cryptosystem using 24-degree primitive polynomial. In this paper we present the concept and various properties of primitive polynomials in Galois field and prove the theorem finding the number of irreducible polynomials and primitive polynomials over $F_p$ when p is larger than 2. This kind of research can be the foundation of finding primitive polynomials of higher security and developing new cipher algorithms using them.