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블록 암호 ARIA에 대한 Flush+Reload 캐시 부채널 공격
배대현(Daehyeon Bae),황종배(Jongbae Hwang),하재철(Jaecheol Ha) 한국정보보호학회 2020 정보보호학회논문지 Vol.30 No.6
하나의 서버 시스템에 여러 운영체제를 사용하거나 사용자간 메모리를 공유하는 클라우드 환경에서 공격자는 캐시 부채널 공격을 통해 비밀 정보를 유출할 수 있다. 본 논문에서는 국내 표준 블록 암호 알고리즘인 ARIA를 사전 연산 테이블 기반 최적화 기법을 이용해 구현할 경우, 캐시 부채널 공격의 일종인 Flush+Reload 공격이 적용되는 것을 확인하였다. ARIA-128을 대상으로 한 Ubuntu 환경에서의 실험 결과, Flush+Reload 공격을 통해 16바이트의 마지막 라운드 키를 찾을 수 있었으며 나아가 마지막 라운드 키와 첫 번째 라운드 키를 이용하면 마스터 키를 찾을 수 있음을 증명하였다. Since the server system in the cloud environments can simultaneously operate multiple OS and commonly share the memory space between users, an adversary can recover some secret information using cache side-channel attacks. In this paper, the Flush+Reload attack, a kind of cache side-channel attacks, is applied to the optimized precomputation table implementation of Korea block cipher standard ARIA. As an experimental result of attack on ARIA-128 implemented in Ubuntu environment, we show that the adversary can extract the 16 bytes last round key through Flush+Reload attack. Furthermore, the master key of ARIA can be revealed from last and first round key used in an encryption processing.
Performance Counter Monitor를 이용한 머신 러닝 기반 캐시 부채널 공격 탐지
황종배(Jongbae Hwang),배대현(Daehyeon Bae),하재철(Jaecheol Ha) 한국정보보호학회 2020 정보보호학회논문지 Vol.30 No.6
최근 마이크로 아키텍처의 취약점을 이용하여 내부의 비밀 정보를 노출시키는 캐시 부채널 공격들이 제안되었다. 캐시 부채널 공격 중 Flush+Reload 공격은 높은 해상도와 낮은 노이즈 특성으로 인해 여러 악의적 응용 공격에 활용되고 있다. 본 논문에서는 CPU 캐시 활동을 관측할 수 있는 PCM(Performance Counter Monitor) 기능을 이용하여 캐시 기반 부채널 공격을 찾아낼 수 있는 탐지기를 구현하였다. 특히, Spectre 공격과 AES 암호 연산 중 비밀 키 추출 공격이 발생했을 때를 가정하여 PCM 카운터 값의 변화를 관측하였다. 실험 결과, PCM의 4가지 카운터 특성이 캐시 부채널 공격에 크게 반응함을 확인하였고, SVM(Support Vector Machine). RF(Random Forest), MLP(Multi Level Perceptron)와 같은 머신 러닝 기반 검출기를 통해 높은 정확도로 캐시 부채널 공격을 탐지할 수 있었다. Recently, several cache side channel attacks have been proposed to extract secret information by exploiting design flaws of the microarchitecture. The Flush+Reload attack, one of the cache side channel attack, can be applied to malicious application attacks due to its properties of high resolution and low noise. In this paper, we proposed a detection system, which detects the cache-based attacks using the PCM(Performance Counter Monitor) for monitoring CPU cache activity. Especially, we observed the variation of each counter value of PCM in case of two kinds of attacks, Spectre attack and secret recovering attack during AES encryption. As a result, we found that four hardware counters were sensitive to cache side channel attacks. Our detector based on machine learning including SVM(Support Vector Machine), RF(Random Forest) and MLP(Multi Level Perceptron) can detect the cache side channel attacks with high detection accuracy.
Noh, Seung Hyo,Hwang, Jeemin,Kang, Joonhee,Seo, Min Ho,Choi, Daehyeon,Han, Byungchan The Royal Society of Chemistry 2018 Journal of Materials Chemistry A Vol.6 No.41
<P>Using first principles DFT calculations and AIMD simulations, we establish a database for catalytic properties of two-dimensional metal-dichalcogenides (2D-TMDs) toward the hydrogen evolution reaction (HER). In addition to conventionally known active sites of edges, we propose that terrace sites can be substantially activated for the HER even without incorporating defects or heteroatom doping. The key idea is to design a heterogeneous 2D-TMD with a bilayer of catalyst/support configuration. We identify the best candidates, NbS2/HfSe2, NbS2/ZrSe2, and TaS2/HfSe2, <I>via</I> high-throughput computational screening of 256 different heterogeneous 2D-TMDs. The expected HER activity is estimated to be comparable to or even better than that of the conventional Pt/C catalyst. It is shown that the Gibbs free energy of hydrogen adsorption can be tuned to an optimal value of 0 eV using heterogeneous 2D-TMD materials. Careful analysis of the first principles database for 2D-TMDs leads to capturing a universal descriptor for the HER activity of 2D-TMDs regardless of hydrogen coverage and active sites: the adhesion energy difference of the catalyst/support TMDs before and after the hydrogen adsorption. The descriptor is linearly correlated with hydrogen adsorption energy. Our design principle for highly functional 2D-TMD catalysts for the HER is, thus, to identify a heterogeneous 2D-TMD of an optimum hydrogen adsorption energy based on adhesion energy difference, which can be accurately and quickly performed <I>via</I> the analysis of the first principles database and validation through experimental measurements.</P>
Hyunkyung Lee,Hyeonseop Lee,Daehyeon Kim,Jinho Jeon,Choongyu Hwang,Sungkyun Park,Jong Mok Ok,Kanghyun Kim,Songkil Kim,Haeyong Kang 한국물리학회 2024 새물리 Vol.74 No.1
To fabricate large-area graphene transistors, the transfer of chemical vapor-deposited grapheme onto preferred substrates and the patterning of drain/source electrodes are necessary. However, these transfer and deposition processes commonly employ polymers such as poly(methyl methacrylate) and photoresists, which can leave residual polymers and adsorbed molecules on the channel, thus affecting the electrical properties of the devices. In this study, we investigated the effects of heat treatment on the device characteristics related to the polymer residues and adsorbates on graphene surface by analyzing the transfer curves. Our findings demonstrate that proper vacuum annealing can enhance the device’s performance and reduce contact resistance. Moreover, we propose an advanced procedure that incorporates thermal annealing under vacuum after each step of polymer removal. This method is particularly beneficial for enhancing the contact and surface properties of channels in general fabrication processes involving polymers.
Lim, Dongwook,Kim, Yoonkyung,Nam, Daehyeon,Hwang, Sungwon,Shim, Sang Eun,Baeck, Sung-Hyeon Elsevier 2018 JOURNAL OF CLEANER PRODUCTION Vol.197 No.1
<P><B>Abstract</B></P> <P>In this paper, Ti/SnO<SUB>2</SUB>-Sb electrodes with different Sb dopant amounts were successfully fabricated on acid-treated Ti substrates by a thermal decomposition method; this was done in an attempt to examine the effect of the doping amount on the electrochemical activity and stability of the electrode. The physicochemical properties of the prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM)-energy-dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). The electrochemical properties were investigated by linear sweep voltammetry (LSV), and the stability was studied via accelerated lifetime testing. The electro-catalytic activity of the prepared Ti/SnO<SUB>2</SUB>-Sb electrodes was strongly dependent on the amount of the Sb dopant, leading to a change in the OER overpotential. Among the prepared samples, the Ti/SnO<SUB>2</SUB> electrode with 10% of a Sb dopant showed the highest catalytic activity for oxygen evolution reaction (OER), and 87% of COD removal with 20 mA cm<SUP>−2</SUP> of current density for 60 min was achieved in the presence of 10.0 g L<SUP>−1</SUP> of chloride. The findings reported herein suggest that the Ti/SnO<SUB>2</SUB> electrode with an optimized Sb dopant amount shows enhanced electro-catalytic performance by easily generating active hydroxyl radicals, which act as strong oxidizing agents.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Ti/SnO<SUB>2</SUB>-Sb electrodes with different amounts of Sb doping were prepared by thermal decomposition. </LI> <LI> The prepared electrodes exhibited a cracked surface morphology and were not crystalline. </LI> <LI> The efficiency of COD elimination depended largely on the amount of Sb. </LI> </UL> </P>