• Journal of Aerospace System Engineering
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• v.13 no.1
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• pp.18-28
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• 2019

High speed vehicles are subjected to high thermal loadings due to aerodynamic heating during ascent and reentry. Since a thermal protection system panel is mechanically constrained, it may cause thermal buckling under excessive thermal loadings. The thermal buckling could disturb the field of flow and make aerodynamic characteristics unstable. It is thus necessary to design the thermal protection system panel to prevent thermal buckling. This study defines the analytical model of temperature distribution using the finite difference method for the thermal protection system panel with large temperature differences inside and outside. This paper proposes the approximate model of the thermal buckling characteristics for the thermal protection system panel through the use of the Ritz method. The validity of the present method was verified by comparing the results of the finite element analysis. Furthermore, this research performs the parametric analysis of the thermal buckling characteristics for the thermal protection system panel by using the approximate model.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.33 no.6
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• pp.1087-1098
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• 2023

The rapid advancement of artificial intelligence (AI) technology has led to its proactive utilization across various fields. However, this widespread adoption of AI-based systems has raised concerns about the increasing threat of attacks on these systems. In particular, deep neural networks, commonly used in deep learning, have been found vulnerable to adversarial attacks that intentionally manipulate input data to induce model errors. In this study, we propose a method to protect image classification models from visually imperceptible One-Pixel attacks, where only a single pixel is altered in an image. The proposed defense technique utilizes an autoencoder model to remove potential threat elements from input images before forwarding them to the classification model. Experimental results, using the CIFAR-10 dataset, demonstrate that the autoencoder-based defense approach significantly improves the robustness of pretrained image classification models against One-Pixel attacks, with an average defense rate enhancement of 81.2%, all without the need for modifications to the existing models.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.34 no.5
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• pp.981-991
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• 2024

Adversarial attacks, which induce malfunctions in AI technologies, can be applied to various domains and models, easily compromising SOTA (State-of-the-Art) models. Although adversarial defense techniques have been developed to counter these attacks, their applicability is limited due to constraints. Consequently, not only is the adoption of AI technology delayed, but also advanced research is restricted. To address this issue, this paper introduces a novel concept of adversarial data by reversing the sign of the loss function update in adversarial attacks. Experiments were conducted by applying the reverse-update adversarial data to data poisoning and adversarial training environments, showing that it can reduce the model's performance up to 72% and is most effective in enhancing robustness in 6 out of 9 environments. Ultimately, the proposed data can stimulate extensive research on adversarial attacks and defenses, further promoting the advancement of defense technology and contributing to the safe adoption of AI.

• Proceedings of the Korea Information Assurance Society Conference
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• 2004.05a
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• pp.181-185
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• 2004

In these days, many reports noticed that the Internet worms spread out and have done considerable damage to all over the world network within a few days. The worms, which is infected from various route such as e-mail, can spread very fast with common property, self replication. But, there is not prepare for the way effectively to interrupt internet worm. Therefore, to prevent our network resource, internet hosts and user clients, the systemic categorization and automatic defense mechanism is required in the Internet worm research. Hence, in this paper, we describe internet worm propagation and defense model.

• 대한방사선방어학회:학술대회논문집
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• 2009.04a
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• pp.112-113
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• 2009

원전주변 환경방사능측정 시료 중 다른 시료와 다르게 저수지는 방사능축적 경향을 확인할 수 있는 가능성이 매우 높다. 본 논문에서는 문제해석의 단순화를 위해 여러 가정의 전제하에 원전주변 저수지의 삼중수소농도계산이 가능한 수치모델을 제안하고 그 결과를 통해 환경방사능 해석에 필요한 값들을 제공하는 방법을 제안하였다. 환경방사능 해석에 제공될 수 있는 값들로는 저수지의 삼중수소농도의 포화여부, 저수지 인근의 삼중수소 농도, 원전으로부터 삼중수소 방출율의 추정, 저수지에 대한 모니터링의 필요성 등이 포함된다.

• Proceedings of the Korean Society of Computer Information Conference
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• 2023.07a
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• pp.619-620
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• 2023

본 논문에서는 AI 모델이 노출될 수 있는 적대적 공격을 연구한 논문이다. AI 쳇봇이 적대적 공격에 노출됨에 따라 최근 보안 침해 사례가 다수 발생하고 있다. 이에 대해 본 논문에서는 적대적 공격이 무엇인지 조사하고 적대적 공격에 대응하거나 사전에 방어하는 방안을 연구하고자 한다. 적대적 공격의 종류 4가지와 대응 방안을 조사하고, AI 모델의 보안 중요성을 강조하고 있다. 또한, 이런 적대적 공격을 방어할 수 있도록 대응 방안을 추가로 조사해야 한다고 결론을 내리고 있다.

• Journal of Internet Computing and Services
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• v.16 no.5
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• pp.1-9
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• 2015

As attacks in cyber space become advanced and complex, monotonous defense approach of one-one matching manner between attack and defense may be limited to defend them. More efficient defense method is required. This paper proposes multi layers security scheme that can support to defend assets against diverse cyber attacks in systematical and adaptive. We model multi layers security scheme based on Defense Zone including several defense layers and also discuss essential technical elements necessary to realize multi layers security scheme such as cyber threats analysis and automated assignment of defense techniques. Also effects of multi layers security scheme and its applicability are explained. In future, for embodiment of multi layers security scheme, researches about detailed architecture design for Defense Zone, automated method to select the best defense technique against attack and modeling normal state of asset for attack detection are needed.

• Journal of Internet Computing and Services
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• v.22 no.1
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• pp.41-50
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• 2021

Cyber Kill Chain is derived from Kill chain of traditional military terms. Kill chain means "a continuous and cyclical process from detection to destruction of military targets requiring destruction, or dividing it into several distinct actions." The kill chain has evolved the existing operational procedures to effectively deal with time-limited emergency targets that require immediate response due to changes in location and increased risk, such as nuclear weapons and missiles. It began with the military concept of incapacitating the attacker's intended purpose by preventing it from functioning at any one stage of the process of reaching it. Thus the basic concept of the cyber kill chain is that the attack performed by a cyber attacker consists of each stage, and the cyber attacker can achieve the attack goal only when each stage is successfully performed, and from a defense point of view, each stage is detailed. It is believed that if a response procedure is prepared and responded, the chain of attacks is broken, and the attack of the attacker can be neutralized or delayed. Also, from the point of view of an attack, if a specific response procedure is prepared at each stage, the chain of attacks can be successful and the target of the attack can be neutralized. The cyber command and control system is a system that is applied to both defense and attack, and should present defensive countermeasures and offensive countermeasures to neutralize the enemy's kill chain during defense, and each step-by-step procedure to neutralize the enemy when attacking. Therefore, thist paper proposed a cyber kill chain model from the perspective of defense and attack of the cyber command and control system, and also researched and presented the threat classification/analysis/prediction framework of the cyber command and control system from the defense aspect

• Information and Communications Magazine
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• v.33 no.2
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• pp.28-38
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• 2016

기존 인터넷의 보안 모델은 모든 통신 상대와 통신 환경에 대한 의심을 기반으로 외부의 공격으로부터 자신을 보호하는 모델이다. 그러나 이 보안 모델은 공격이 지능화됨에 따라 방어도 지속적으로 강화되어야 하는 악순환의 고리에 빠지게 된다. 이런 악순환의 고리를 끊기 위하여 상호 신뢰를 바탕으로 공격자체가 원천적으로 없어지는 신뢰통신 구조를 제안한다. 신뢰통신모델은 먼저 상호신뢰 관계를 가진 제한된 참여자들로 구성된 신뢰 도메인에서 시작하여 외부와의 통신은 잘 정의된 인증 절차에 따라 허용함으로써 도메인의 신뢰 수준을 유지하면서 신뢰 영역을 확장하는 방식을 채택한다. 이 신뢰 모델을 기반으로 신뢰 네트워크 구조를 제안하고 이 구조를 기존의 IP 네트워크에 적용하는 방안을 제시한다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.12
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• pp.2649-2656
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• 2012

Today, many enterprises have invested heavily for the part of information security in order to protect the internal critical information assets and the business agility. However, there is a big problem that big budget and too many manpower are needed to set the internal corporate network up to the same high level of defense for all of part. On the distributed enterprise networks in this paper, a defense model for effective and rapid response on the IP spoofing attack was designed to protect the enterprise network through the exchange of information between the trust hosts when an attacker attacked any target system using other trusted host.