• The KIPS Transactions:PartC
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• v.13C no.1 s.104
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• pp.11-18
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• 2006

In the field of network defense, a lot of researches are directed toward locating the source of network attacks. When an intruder launches attack not from their own computer but from intermediate hosts that they previously compromised, and these intermediate hosts are called stepping-stones. There we two kinds of traceback technologies : IP packet traceback and connection traceback. We focused on connection traceback in this paper This paper classifies process structures of detoured attack type in stepping stone, designs an algorithm for traceback agent, and implements the traceback system based on the agent

• The KIPS Transactions:PartC
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• v.13C no.4 s.107
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• pp.441-446
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• 2006

In recent years, WDM networks have received much attention as the Internet backbone networks because of the explosive growth of the Internet IP-based traffic. The Optical Burst Switching (OBS) has been proposed as an effective optical switching technology in the WDM networks. The OBS has the advantages in 1) the high usage rate of the bandwidth, and 2) no necessity of optical buffer. However, the OBS has the burst-contention problem in the networks. The deflection routing is proposed as one of means to solve this problem. In this paper, we propose a new routing method to minimize burst loss in the deflection routing based networks. In addition, we propose a QoS control method using a new routing algorithm. Finally, we show the variety of the proposed methods by computer simulations.

• International Journal of Highway Engineering
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• v.11 no.3
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• pp.129-139
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• 2009

The transportation network is a critical infrastructure in the event of natural and human caused disasters such as rainfall, snowfall, and terror and so on. Particularly, the transportation network in an urban area where a large number of population live is subject to be negatively affected from such events. Therefore, efficient traffic operation plans are required to assist rapid evacuation and effective detour of vehicles on the network as soon as possible. Recently, ubiquitous communication and sensor network technology is very useful to improve data collection and connection related emergency information. In this study, we develop a specific algorithm to provide evacuation route and detour information only for vehicles under emergency situations. Our algorithm is based on shortest path search technique and dynamic traffic assignment. We perform the case study to evaluate model performance applying hypothetical scenarios involved terror. Results show that the model successfully describe effective path for each vehicle under emergency situation.

• Journal of Korean Electronics
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• v.24 no.8
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• pp.44-47
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• 2004

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1992.04b
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• pp.263-263
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• 1992

• Journal of Korean Electronics
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• v.9 no.5
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• pp.31-34
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• 1989

• Journal of the Korea Institute of Information Security & Cryptology
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• v.30 no.5
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• pp.881-893
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• 2020

CFI(Control Flow Integrity) is a mitigation mechanism that protects programs by verifying control flows. IFCC(Indirect Function Call Checks) and SCS(Shadow Call Stack), CFI supported by LLVM Clang compiler, were introduced to protect applications in Android. IFCC protects function calls and SCS protects function returns. In this paper, we propose attacks to bypass CFI on the application environment with IFCC and SCS. Even if IFCC and SCS were applied to user applications, it was confirmed that there were many code segments not protected by IFCC and SCS in the application memory. We execute code in CFI unprotected segments to construct 1) bypassing IFCC to call a protected function, 2) modulating return address via SCS bypass. We identify code segments not protected by IFCC and SCS in Android10 QP1A. 191005.007.A3. We also implement proof-of-concept exploits to demonstrate that modulation of control flow is possible in an environment where IFCC and SCS are applied.

• KIPS Transactions on Computer and Communication Systems
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• v.10 no.11
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• pp.297-304
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• 2021

Commercial obfuscation tools (protectors) aim to create difficulties in analyzing the operation process of software by applying obfuscation techniques and Anti-reversing techniques that delay and interrupt the analysis of programs in software reverse engineering process. In particular, in case of virtualization detection and anti-debugging functions, the analysis tool exits the normal execution flow and terminates the program. In this paper, we analyze Anti-reversing techniques of executables with Debugger Detection and Viralization Tools Detection options through VMProtect 3.5.0, one of the commercial obfuscation tools (protector), and address bypass methods using Pin. In addition, we predicted the location of the applied obfuscation technique by finding out a specific program termination routine through API analysis since there is a problem that the program is terminated by the Anti-VM technology and the Anti-DBI technology and drew up the algorithm flowchart for bypassing the Anti-reversing techniques. Considering compatibility problems and changes in techniques from differences in versions of the software used in experiment, it was confirmed that the bypass was successful by writing the pin automation bypass code in the latest version of the software (VMProtect, Windows, Pin) and conducting the experiment. By improving the proposed analysis method, it is possible to analyze the Anti-reversing method of the obfuscation tool for which the method is not presented so far and find a bypass method.

• Journal of Chest Surgery
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• v.35 no.3
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• pp.182-187
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• 2002

Background: There have been many reports of coronary angiographic findings after coronary bypass grafting, most of which are focused on the graft patency rate of the bypass conduits. However, postoperative angiography can provide numerous informations other than patency rates that are useful for establishing operative strategy. Material and Method: We studied 73 patients in whom coronary angiography was done after more than 1 month of CABG. Mean interval from the operation to coronary angiography was 10.6 months and the reasons for coronary angiography follow up were residual or recurrent angina in 54 patients, abnormalities on myocardial perfusion scan or echocardiography in 13 patients, and for simple follow up in 6 patients. Result: Overall graft patency rate was 80.9% (internal thoracic artery 100%, saphenous vein 75.0%) in patients of simple follow up and 61.6%(internal thoracic artery 81.1%, saphenous vein 55.3%) in patients with ischemia. Progression of native coronary arterial disease proximal to the grafting site was found in 50 patients(68.5%). Among 201 coronary arterial branches that had not been completely occluded preoperatively, ninty five branches(47.3%) revealed progression of diameter stenosis by more than 20% on the follow up study. Among them, 64 branches(31.8%) progressed to total occlusion. The incidence of disease progression was highter in the coronary arteries with patent grafts(57.5%) than in those with occluded grafts(36.3%)(p<0.05), Comparing internal thoracic artery graft with saphenous vein graft, internal thoracic artery was superior to saphenous vein, not only in terms of patency(83.3% vs 56.6%), but also in terms of result of later percutaneous intervention success rate(100% vs 62%, p<0.05). Conclusion: Due to the considerable incidence of progression of native coronary artery stenosis in the early postoperative periods, bypass grafting of a vessel with borderline stenosis, especially with vein graft, must be done prudently. And it was confirmed again that revascularization of left anterior descending artery is most important and that internal thoracic artery was superior to saphenous vein.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.10a
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• pp.517-518
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• 2013

모바일 에드 혹 네트워크(Mobile Ad hoc Network)는 이동성을 가진 노드로 구성된 네트워크로서, 통신기반 시설의 지원이 없어도 스스로 통신망을 구축하여 통신한다. 하지만 노드의 이동성으로 인한 토폴로지의 변화가 빈번하여, 라우팅 경로 재설정으로 인한 오버헤드가 생성된다. 오버헤드 생성을 줄이기 위하여 클러스터링을 이용한 연구가 진행되어 왔다. 클러스터가 형성된 MANET에서 클러스터 헤드 노드가 이동함에 따라 클러스터 영역을 벗어나게 되었을 경우, 클러스터 그룹에 속하는 멤버 노드들은 패킷을 보내지 못하며, 클러스터 헤드노드를 선출하지 못하여 사용할 수 없는 노드가 된다. 본 논문에서는 클러스터 헤드 노드가 클러스터 영역을 벗어날 경우, 클러스터 멤버노드의 상황인자 속성 벡터 정보가 유사한 클러스터 헤드노드를 이웃한 주변 클러스터 헤드로부터 검색 및 선택하여, 우회경로를 제공하는 알고리즘을 제안한다. 제안된 알고리즘에서 각 노드는 상황정보 매트릭스를 가지고 있어, 전송 커버리지 영역이 2홉 이내 반경에 있는 노드의 벡터 정보를 저장하게 된다. 클러스터 헤드 노드와의 연결이 끊어 졌을 경우, 클러스터 멤버 노드는 상황정보 매트릭스를 이용하여, 벡터정보가 유사한 클러스터 헤드 노드를 선택하여, 노드 간의 연결성 및 패킷의 전달성이 향상 된다.