• Convergence Security Journal
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• v.15 no.2
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• pp.81-89
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• 2015

HIGHT is an 64-bit block cipher, which is suitable for low power and ultra-light implementation that are used in the network that needs the consideration of security aspects. This paper presents a key scheduler that employs the presented LFSR and reverse LFSR that can generate four outputs simultaneously. In addition, we construct new key scheduler that generates 4 subkey bytes at a clock since each round block requires 4 subkey bytes at a time. Thus, the entire HIGHT processor can be controlled by single system clock with regular control mechanism. We synthesize the HIGHT processor using the VHDL. From the synthesis results, the logic size of the presented key scheduler can be reduced as 9% compared to the counterpart that is employed in the conventional HIGHT processor.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.26 no.3
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• pp.623-630
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• 2016

Heterogeneous IoT devices must satisfy a certain level of security for mutual connections and communications. However, a performance degradation of cryptographic algorithms in resource constrained devices is inevitable and so an optimization or efficient implementation method is necessary. In this paper, we study an efficient implementation method for rotation operations regarding registers for running ARX lightweight block ciphers. In a practical sense, we investigate the performance of modified rotation operations through experiments using real experiment devices. We show the improved performance of modified rotation operations and discover the significant difference in measured performance between simulations and real experiments, particularly for 16-bit MSP microcontrollers.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.15 no.1
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• pp.99-107
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• 2005

ARIA is a 128-bit block cipher having 128-bit, 192-bit, or 256-bit key length. The cipher is a substitution and permutation encryption network (SPN) and uses an involutional binary matrix. This structure was efficiently developed into light weight environments or hardware implementations. This paper shows that a careless implementation of an ARIA on smartcards is vulnerable to a differential power analysis attack This attack is realistic because we can measure power consumption signals at two kinds of S-boxes and two types of substitution layers. By using the two round key, we extracted the master key (MK).

• Journal of Internet Computing and Services
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• v.24 no.5
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• pp.85-96
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• 2023

With advance of cloud computing technology, Blockchain as a Service of Cloud Service Provider has been utilized in various areas such as e-Commerce and financial companies to manage customer history and distribution history. However, if users' search history, purchase history, etc. are to be utilized in a BaaS in areas such as recommendation algorithms and search engine development, the users' search queries will be exposed to the company operating the BaaS, and privacy issues will be occured. Z. Guan et al. ensure the unlinkability between users' search query and search result using searchable encryption, and based on the inner product similarity, they select Top-k results that are highly relevant to the users' search query. However, there is a problem that the Top-k results selection may be not possible due to ties of inner product similarity, and BaaS over cloud is not considered. Therefore, this paper solve the problem of Z. Guan et al. using cosine similarity, so we improve accuracy of search result. And based on this, we design a BaaS with secure Top-k search that improved accuracy. Furthermore, we design a smart contracts that preserve privacy of users' search and obtain Top-k search results that are highly relevant to the users' search.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.10 no.4
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• pp.3-11
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• 2000

In this paper, we design modular multiplication systolic array and exponentiation processor having n bits message black. This processor uses Montgomery algorithm and LR binary square and multiply algorithm. This processor consists of 3 divisions, which are control unit that controls computation sequence, 5 shift registers that save input and output values, and modular exponentiation unit. To verify the designed exponetion processor, we model and simulate it using VHDL and MAX+PLUS II. Consider a message block length of n=512, the time needed for encrypting or decrypting such a block is 59.5ms. This modular exponentiation unit is used to RSA cryptosystem.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.33 no.3
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• pp.471-485
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• 2023

Recently, due to the nature of blockchain that guarantees users' anonymity, more and more cases are being exploited for crimes such as illegal transactions. However, cryptocurrency is protected in cryptocurrency wallets, making it difficult to recover criminal funds. Therefore, this study acquires artifacts from the data and memory area of a local PC based on user behavior from four browser extension wallets (Metamask, Binance, Phantom, and Kaikas) to track and retrieve cryptocurrencies used in crime, and analyzes how to use them from a digital forensics perspective. As a result of the analysis, the type of wallet and cryptocurrency used by the suspect was confirmed through the API name obtained from the browser's cache data, and the URL and wallet address used for the remittance transaction were obtained. We also identified Client IDs that could identify devices used in cookie data, and confirmed that mnemonic code could be obtained from memory. Additionally, we propose an algorithm to measure the persistence of obtainable mnemonic code and automate acquisition.

• Journal of Broadcast Engineering
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• v.22 no.5
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• pp.643-651
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• 2017

Steganography is one of information hiding technologies and discriminated from cryptography in that it focuses on avoiding the existence the hidden information from being detected by third parties, rather than protecting it from being decoded. In this paper, as an image steganography method which uses images as media, we propose a new block matching method that embeds information into the discrete wavelet transform (DWT) domain. The proposed method, based on a statistical analysis, reduces loss of embedding capacity due to inequable use of candidate blocks. It works in such a way that computes the variance of each candidate block, preserves candidate blocks with high frequency components while reducing candidate blocks with low frequency components by compressing them exploiting the k-means clustering algorithm. Compared with the previous block matching method, the proposed method can reconstruct secret images with similar PSNRs while embedding higher-capacity information.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.25 no.2
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• pp.271-278
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• 2015

We use various types of cryptographic algorithms for the protection of personal and sensitive informations in the application environments, such as an internet banking and an electronic commerce. However, recent researches were introduced that if we implement modes of operation, padding method and other cryptographic implementations in a wrong way, then the critical information can be leaked even though the underlying cryptographic algorithms are secure. Among these attacking techniques, the padding oracle attack is representative. In this paper, we analyze the possibility of padding oracle attacks of 12 kinds of padding techniques that can be applied to the CBC operation mode of a block cipher. As a result, we discovered that 3 kinds were safe padding techniques and 9 kinds were unsafe padding techniques. We propose 5 considerations when designing a safe padding techniques to have a resistance to the padding oracle attack through the analysis of three kinds of safe padding techniques.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.12 no.4
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• pp.87-98
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• 2002

Software has been developed very fast as information has become important value. Illegal software copy has been the main problem of developing software business. Recently used protecting lock system for software copy has not guaranteed perfectly from easily cracked-defense system. This paper, therefore, proposes 96-bit block cipher with 112-bit length to replace a DES(Data Encryption Standard) algorithm. Security chip by ASIC(Application Specific Integrated Circuit) security module is presented for software copy protection. Then, an auto block protecting algorithm is designed for the security chip. Finally, controlling driver and library are built for the security chip.

• Proceedings of the Korea Institutes of Information Security and Cryptology Conference
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• 2006.06a
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• pp.148-152
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• 2006

스마트카드에 대한 전자파 분석 공격은 스마트카드 내의 마이크로프로세서가 연산될 때, 방사하는 의도되지 않은 전자파를 수집하여 비밀정보를 알아내는 공격이다. 이 경우에는 스마트카드에 어떤 훼손도 가하지 않고 비밀정보를 알아낼 수 있어, 기존에 국내외적으로 활발히 연구된 전력 분석 공격보다 더욱 현실적이고, 강력한 공격이다. 본 논문은 국내에서는 처음으로 스마트카드에 대한 전자파 분석 공격인 SEMA와 DEMA 공격 실험을 하였다. 그 결과 공개키 알고리즘인 RSA에 SEMA 공격을 성공하였고, 이에 대한 방어대책을 적용하여 방어를 하였다. 그리고, 국내 표준 블록 암호 알고리즘인 ARIA에 DEMA 공격을 적용하여, 비밀키를 알아냈다.