• Proceedings of the Korea Information Processing Society Conference
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• 2013.05a
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• pp.675-678
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• 2013

암호 알고리즘이 탑재된 환경에서 암호 알고리즘의 이론적 안전성이 고려되어도 환경에 의존한 부가적 정보를 활용하는 부채널 분석에 대한 안전성이 검토되어야 한다. 최근까지 부채널 분석에 대한 안전성을 고려한 대응기법으로 마스킹 기법이 적용되었으나, 이와는 상반된 개념인 하드웨어 DPL(Dual-rail with Precharge Logic) 기법을 응용한 균일한 해밍웨이트를 제공하는 소프트웨어 AES(Advanced Encryption Standard)가 제안되었다. 최근, 소프트웨어 기반 블록암호에 대해 고차 마스킹 부채널 대응법의 비효율성으로 새로운 방법에 대한 다양한 시도가 되고 있으며, 그 중 균일한 해밍웨이트를 제공하는 표현 방법이 효율적이고 안전한 새로운 대응법으로 검토되어지고 있다. 하지만, 논문에서는 균일한 해밍웨이트 데이터 표현방법 기반 부채널 대응법을 해독하는 차분전력분석 방법을 소개한다. 실험을 통해, AES 128비트 키 중 일부분이 분석됨을 확인하였다. 이는 공격자가 테이블 변환 정보를 활용할 수 있다는 다소 강력한 가정하에 실험하였기 때문이다. 앞선 가정 하에 안전성을 제공하기 위해서는 차후 추가적 대응기법이 고려되어야 한다.

• Proceedings of the Korea Information Processing Society Conference
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• 2023.05a
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• pp.212-214
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• 2023

동형암호는 주목받는 차세대 프라이버시 보존 기술이다. 많은 기업들이 이를 활용한 서비스들을 제공하고 있다. 비록 동형암호가 수학적으로 안전성을 인정받았지만, 실행되는 프로그램으로써 동형암호는 부채널공격들에 취약하다는 연구 결과들이 보고되고 있다. 이 논문은 이런 부채널공격들에 대해 본석, 일반화하여 사용 가능한 gadget을 소개하며, 대응기법에 대한 가이드라인을 제안하고 그 효과와 한계에 대해 분석한다.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.24 no.6
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• pp.1045-1053
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• 2014

In this paper, we assume that the information leakage through side-channel signal may occur from the card payment terminal and newly introduce a real application attack model. The attack model is a side channel attack based on vibration signals, which are detected by a small sensor attached on card terminal by attacker. This study is similar to some other studies regarding side channel attack. However, this paper is different in that it is based on the non-language model. Because the financial transaction information such as a card number, password, mobile phone number and etc cannot have a constant pattern. In addition, there was no study about card terminal. Therefore, this new study is meaningful. We collected vibration signals on card terminal with a small wireless sensor and analyzed signal data with statistical signal processing techniques using spectrum of frequency domain and principal component analysis and pattern recognition algorithms. Finally, we evaluated the performances by using real data from the sensor.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.17 no.5
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• pp.65-72
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• 2007

In this paper, we investigate the several different types of higher-order differential side channel analysis (DSCA) attacks. We present that some of exiting higher-order DSCA attacks have some practical problem applying to two masked intermediate values being parallel processed. In order to solve this problem we propose a new higher-order DSCA attack using an efficient and simple preprocessing function. Using the proposed preprocessing function we clearly show that 2nd-order DSCA attacks are still a practical threat fur masked hardware implementations.

• Proceedings of the Korea Information Processing Society Conference
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• 2019.10a
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• pp.449-452
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• 2019

초 경량암호 CHAM은 자원이 제한된 장치 상에서 효율성이 뛰어난 덧셈, 회전연산, 그리고 XOR 연산으로 이루어진 알고리즘이다. CHAM은 특히 사물인터넷 플랫폼에서 높은 연산 성능을 보인다. 하지만 사물 인터넷 상에서 사용되는 경량 블록 암호화 알고리즘은 부채널 분석에 취약할 수 있다. 본 논문에서는 CHAM에 대한 1차 전력 분석 공격을 시도하여 부채널 공격에 대한 취약성을 증명한다. 이와 더불어 해당 공격을 안전하게 방어할 수 있도록 마스킹 기법을 적용하여 안전한 알고리즘을 제안한다.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.21 no.1
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• pp.153-166
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• 2011

Recent trends in mobile device market whose services are rapidly expanding to provide wireless internet access are drawing people's attention to mobile security. Especially, since threats to information leakage are reaching to the critical level due to the frequent interchange of important data such as personal and financial information through wireless internet, various encryption algorithms has been developed to protect them. The encryption algorithms confront the serious threats by the appearance of side channel attack (SCA) which uses the physical leakage information such as timing, and power consumption, though the their robustness to threats is theoretically verified. Against the threats of SCA, researches including the performance and development direction of SCA should precede. Among tile SCA methods, the power analysis (PA) attack overcome this misalignment problem. The conventional methods require large computational power and they do not effectively deal with the delay changes in a power trace. To overcome the limitation of the conventional methods, we proposed a novel alignment method using peak matching. By computer simulations, we show the advantages of the proposed method compared to the conventional alignment methods.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.29 no.4
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• pp.709-718
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• 2019

A lightweight block cipher CHAM designed for suitability in resource-constrained environment has reasonable security level and high computational performance. Since this cipher may contain intrinsic weakness on side channel attack, it should adopt a countermeasure such as masking method. In this paper, we implement the masked CHAM cipher on 32-bit microprosessor Cortex-M3 platform to resist against side channel attack and analyze their computational performance. Based on the shortcoming of having many round functions, we apply reduced masking method to the implementation of CHAM cipher. As a result, we show that the CHAM-128/128 algorithm applied reduced masking technique requires additional operations about four times.

• Proceedings of the Korea Information Processing Society Conference
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• 2021.05a
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• pp.171-174
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• 2021

최근 사물인터넷(IoT) 환경에서 다양한 장비의 인터넷 통신이 가능하여 이에 적절한 경량 블록 암호 알고리즘에 대한 연구가 활발히 진행되고 있다. ICISC 2020에서 새로 발표된 국산 경량 블록 암호 알고리즘인 PIPO는 새로운 경량 S-Box를 조합한 unbalanced-Bridge 구조로 효율적인 비트슬라이싱 구현을 제공한다. IoT 환경에 PIPO가 적용되기 위해서는 부채널 분석에 대한 안전성이 보장되어야 한다. 따라서 본 논문에서는 PIPO가 1차 CPA 공격에 취약함을 확인한다. 그리고 부채널 공격에 대응하기 위해 1차 마스킹 기법을 제안한다. 제안한 마스킹 기법은 1차 CPA 공격에 안전하였으며, 마스킹 적용 전보다 -375%의 성능을 보였다. 그리고 기존 기법보다 1287% 속도가 빨라진 것을 확인하였다.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.14 no.6
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• pp.125-134
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• 2004

When cryptosystem designers implement devices that computing power or memory is limited such as smart cards, PDAs and so on, not only he/she has to be careful side channel attacks(SCA) but also the cryptographic algorithms within the device has to be efficient using small memory. For this purpose, countermeasures such as Moiler's method, Okeya-Takagi's one and overlapping window method, based on window method to prevent SCA were proposed. However, Moiler's method and Okeya-Talngi's one require additional cost to prevent other SCA such as DPA, Second-Order DPA, Address-DPA, and so on since they are immune to only SPA. Also, overlapping window method has a drawback that requires big memory. In this paper, we analyze existing countermeasures and propose an efficient and secure countermeasure that is immune to all existing SCA using advantages of each countermeasure. Moreover, the proposed countermeasure can enhance the efficiency using mixed coordinate systems.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.32 no.4
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• pp.607-615
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• 2022

The SITM (See-In-The-Middle) proposed in CHES 2020 is a methodology for side-channel assisted differential cryptanalysis. This technique analyzes the power traces of unmasked middle rounds in partial masked SPN block cipher implementation, and performs differential analysis with the side channel information. Blockcipher GIFT is a lightweight blockcipher proposed in CHES 2017, designed to correct the well-known weaknesses of block cipher PRESENT and provide the efficient implementation. In this paper, we propose SITM attacks on partial masked implementation of GIFT-128. This attack targets 4-round and 6-round masked implementation of GIFT-128 and time/data complexity is 2^14.01 /2^14.01, 2¹⁶ /2¹⁶. In this paper, we compare the masterkey recovery logic available in SITM attacks, establishing a criterion for selecting more efficient logic depending on the situation. Finally, We introduce how to apply the this attack to GIFT-COFB, one of the finalist candidates in NIST lightweight cryptography standardization process.