iOS knowledgeC.db 활용 삭제된 메신저 앱 사용 행위추적 방안 연구

안치현,이상진,박정흠 한국디지털포렌식학회 2024 디지털 포렌식 연구 Vol.18 No.1

iOS 시스템 로그 중 하나인 knowledgeC.db에는 다양한 사용자 행위 및 기기의 동작이 기록된다. 특히 메신저 앱이 동작하였을 때 기록되는 로그의 경우, 유저 ID, 닉네임, 채팅방 ID, 메시지 송·수신 행위, 통화 수·발신 행위, 타임스탬프 등 포렌식적으로 가치 있는 데이터가 다수 존재한다. 해당 로그는 기기에서 메신저 앱이 삭제되더라도 일정 기간 보존되어 사용자 행위 추적이 가능하다. 본 논문에서는 5가지 메신저 앱을 이용하여 사용자 행위를 수행하고 메신저 앱을 삭제한 후 knowledgeC.db를 수집·분석하였으며, 보존된 로그에서 확보할 수 있는 정보와 보존 기간을 파악하였다. 또한 iOS 16부터 knowledgeC.db의 데이터를 대체한다고 알려진 Biome의 SEGB 파일에 기록된 로그와 knowledgeC.db의 로그를 비교 분석하였으며, 이를 통해 메신저 앱 삭제 행위에 대응하기 위한 knowledgeC.db의 조사 방법을 제안한다. “knowledgeC.db”, known as an iOS system artifact, records a user’s messenger app activity. When a messenger app is deleted, logs in knowledgeC.db sustain for some period of time. These logs are forensically useful when investigating the user’s activity related to the deleted messenger app. There exist studies and tools to parse knowledgeC.db. However, when it comes to countering anti-forensic behavior and understanding the actual meaning of the remaining data, further research is still needed. In this paper, we analyze the structure of knowledgeC.db from a forensic perspective, after conducting tests with 5 messenger apps. Through tests, we attempt to figure out timestamp data, user identifiable information, user activity types, and the duration for which logs are maintained even after the apps had been uninstalled. Also, we compare the logs in the knowledgeC.db with the Biome SEGB files, which are known to substitute data in knowledgeC.db from iOS 16. Eventually, we propose a tool for automation and suggest a methodological approach to utilize knowledgeC.db for forensic investigation.

신규 산업분류체계 사용에 따른 산업 내 동질성 증가 효과 분석: 한국표준산업분류와 글로벌산업분류기준 비교

안치현,허성준 한국경영교육학회 2019 경영교육연구 Vol.34 No.1

[Purpose]The purpose of this study is to verify whether the industrial classification based on the new industry classification standard, which was not covered in the previous research, reflects the homogeneity in the industry better than the existing industrial classification system in Korea. [Methodology]We analyze whether there is a significant difference in industrial homogeneity between industrial classification systems based on the global industrial classification standard and the Korean standard industrial classification by using widely used market indicators in capital market research. [Findings]The seven of eleven indicators widely used in the capital market show significantly higher industrial homogeneity when measured by the global industry classification standard. The result suggests that firms have better homogeneity in the industry classified by the global industry classification standard. [Implications]This study is to introduce the global industry classification standard in domestic capital market research and to investigate whether it can replace the existing industry classification standard. It is expected that it will have implications to relevant government agencies and financial authorities. [연구목적]본 연구에서는 기존 연구에서는 다루지 않았던 새로운 산업분류기준에 의한 산업분류가 산업 내 동질성을 기존 산업분류체계보다 잘 반영하고 있는지 검증하였다. [연구방법]본 연구는 Bhojraj et al.(2003)과 Hrazdil et al.(2013)의 연구방법과 동일하게 자본시장 및 실무적으로 널리 사용되는 시장지표를 이용하여 글로벌산업분류기준과 한국표준산업분류에 의해 분류된 산업군의 동질성이 두 산업분류체계 간 유의한 차이가 발생하는지 분석하였다. [연구결과]자본시장에서 널리 사용되는 11개의 지표 중 7개의 지표에서 글로벌산업분류기준으로 측정하였을 때 산업 내 동질성이 유의하게 높게 나타나, 글로벌산업분류기준으로 분류된 기업들의 산업 내 동질성이 보다 증가하는 것으로 나타났다. [연구의 시사점]국내 자본시장 연구에서 글로벌산업분류기준을 소개하고 기존 산업분류기준을 대체할 만한 것인지를 살펴본 최초의 연구라는 점에서 공헌점을 가진다. 투자자들이 국가단위보다 업종단위로 기업을 평가하고 이에 따른 투자패턴이 세계공통의 업종기준에 의해 이루어지고 있는 상황에서 국내․외 및 신규 투자자들이 직관적으로 이해하기 쉬운 글로벌산업분류기준을 알리고, 기존 산업분류체계보다 분류상 우수성이 있는지를 검증하였다는 점에서 시사점을 가질 것으로 기대된다.

계층 구조에서 F-SNOOP을 적용한 선택적 버퍼링 매크로 핸드오버

안치현,김동현,김형철,유황빈,이대영,전계석,Ahn Chi-Hyun,Kim Dong-Hyun,Kim Hyoung-Chul,Ryou Hwang-Bin,Lee Dae-Young,Jun Kye-Suk 한국통신학회 2006 韓國通信學會論文誌 Vol.31 No.5b

HMIPv6는 MAP(Mobility Anchor Point)라고 불리는 프로토콜 요소를 도입하여 로컬 핸드오버 시 MN(Mobile Node)에 대한 전송 지연과 외부 네트워크로의 시그널링 로드를 줄이는데 그 의미를 가지고 있다. 하지만 로컬지역의 핸드오버가 아닌 메크로 핸드오버의 경우 기존의 MIPv6의 핸드오버를 그대로 이용하고 있기 때문에 패킷손실과 전송 지연에 대한 문제점이 발생한다. 본 논문에서는 계층적인 구조에서 매크로 핸드오버 발생 시 CN와 MN 사이의 거리, NAR(New Access Router)와 MN 사이의 거리를 계산하여 기준값을 생성하고 그에 맞는 버퍼링 핸드오버를 선택하는 메커니즘을 제안한다. 또한 그러한 핸드오버에 알맞은 무선망에서의 성능개선을 위해 F-SNOOP을 도입한다. 무선망은 패스로스, 페이딩, 잡음, 간섭 등의 이유로 높은 에러율의 특성을 갖고 있어 혼잡과 무관하게 많은 패킷 손실이 발생하고 있다. TCP는 이를 혼잡으로 여겨 혼잡제어를 하여 패킷 전송율이 낮아지는데 F-SNOOP은 SNOOP 프로토콜을 기반으로 핸드오프 시 혼잡제어지연 기법인 Freeze-TCP의 ZWA(Zero Window Advertisement) 메시지를 이용하여 무선망의 TCP의 성능을 향상시킨다. HMIPv6 is designed to reduce the signaling load to external network and improve handover speed of MN by including Mobility Anchor Point(MAP) in local handover. However in this case of macro handover, it's just used pervious MIPv6 handover algorithm. So, it occurs packet loss and transmission delay problem. In this paper, we propose the mechanism applying the HMIPv6 for Fast Handover to choose suitable to the condition buffering handover. The condition for the selection is result distance measurement between MN and CN, between MN and NAR. Furthermore, using F-SNOOP protocol, it is possible to improve wireless network performance. Wireless network has high Bit Error Rate(BER) characteristic because of path loss, fading, noise and interference. TCP regards such errors as congestion and starts congestion control. This congestion control makes packet transmission rate low. However, F-SNOOP improves TCP performance based on SNOOP and Freeze TCP that use Zero Window Advertisement(ZWA) message when handoff occurs in wireless network.

성인 상악 전치 형태에 따른 치은의 임상적 소견

안치현,허수례,조익현,김형섭,An, Chi-Hyun,Heo, Soo-Rye,Cho, Ik-Hyun,Kim, Hyung-Seop 대한치주과학회 2005 Journal of Periodontal & Implant Science Vol.35 No.2

It has been suggested that morphologic characteristics of the periodontium are partly related to the shape and form of the teeth. Furthermore, the severity of symptoms of periodontal disease have been proposed to differ among these various morphologic entities or "biotypes". The purpose of the present study was to examine the relationship between the form of the crowns in the maxillary anterior tooth segment and (1) a group of morphological characteristics and (2) the thickness of the gingiva. The thickness of gingiva was measured by ultrasonic device(SDM). 100 subjects devoid of symptoms of destructive periodontal disease were examined regarding, e.g., probing depth, gingival recession, width of keratinized gingiva, thickness of the keratinized gingiva. From maxillary study cast, the width(at the apical third-CW) and the length(CL) of the crowns of the 6 anterior teeth were determined. A CW/CL-ratio was calculated for each tooth and averaged for each tooth region. The individual mean CW/CL-ratio values for the central incisors were ranked. The 10 subjects ranked highest and the 10 ranked lowest were selected as having either a long-narrow(group N) or a short-wide(group W) form of the crown of the tooth. The data for each of the examined parameters were averaged for each tooth region in each subject and mean values for subjects in groups W and N were compared using the Student t-test. Stepwise multiple regression analysis, including data from the whole sample, was performed for each tooth region with the thickness of the free gingiva as the dependent variable. The results from the analyses demonstrated that individuals with a long-narrow form of the central incisors displayed, compared to individuals with a short-wide crown, form (l) a narrow zone of keratinized gingiva, (2) a pronounced "scalloped" contour of the gingival margin. There was no significant difference between groups N and W with respect to the thickness of the keratinized gingiva. The CW/CL-ratio data revealed that a certain form of the crowns in the central incisors was accompanied by a similar form in the lateral incisors and canine tooth region. The regression analyses demonstrated that the thickness of the keratinized gingiva in central, lateral incisors and canines was significantly related to the width of the keratinized gingiva.

계층 구조에서 F-SNOOP을 적용한 선택적 버퍼링 매크로 핸드오버

안치현,김동현,김형철,유황빈,이대영,전계석 한국통신학회 2006 韓國通信學會論文誌 Vol.31 No.5

System Design for Energy Efficiency Optimization of HVAC System

안치현,김상원,최인호 한국정보기술학회 2013 JOURNAL OF ADVANCED INFORMATION TECHNOLOGY AND CON Vol.3 No.2

In this study, the HVAC(Heating, Ventilation, Air Conditioning) system is designed based on the model in which the HVAC fan driving type and hybrid charging type are combined together to optimize the energy efficiency of the HVAC system by applying eco-friendly photovoltaic power generation. The efficiency increased by approximately 10% when the DC step down converter, also known as a buck converter that has a circuit with the input and output sharing the same ground, was used and applied in the HVAC blower motor. At the same time, the system was also designed to supply electric power as an auxiliary power source to the alternator and to charge the battery as a boost by making use of the LTC3814-5, which is a chip exclusively for the DC-DC step up converters. In order to confirm the efficiency of the proposed system, operating experiment and vehicle performance evaluation were conducted.

Adaptive Selective Wireless-TCP by Type of Error

안치현,김형철,곽윤식 한국정보기술학회 2013 JOURNAL OF ADVANCED INFORMATION TECHNOLOGY AND CON Vol.3 No.2

Wireless network has high BERs because of its path losses, fading, noises and interferences. In the MIP environments, errors in wireless network are divided random error and burst error. Particularly, busty errors is increased the RTO greatly and is initialized window size. So as a result, affect the transfer rate significantly. To solve such problem, In this paper, we propose SSF-TCP that loads enhanced MF-SNOOP modules on the MAP to keep continuous TCP connection in the MIP whenever the handover happens. the paper proposes the SSF-TCP (Selective Snoop with Freeze-TCP) that loads Enhanced MF-SNOOP modules on the MAP in HMIP and maintains TCP connectivity during network layer handovers. The proposed protocol is to predict the random and burst error. So, the number of re-transmission packets is adjusted. Thereafter, as soon as MN in MIP finishes the handover, MN immediately receives its packets.

The System for MPPT (Maximum Power Point Tracker)

안치현,김상원,최인호 한국정보기술학회 2013 JOURNAL OF ADVANCED INFORMATION TECHNOLOGY AND CON Vol.3 No.1

In this paper, we design the car-based solar power controller that makes the HVAC fan (HAVC blower motor) drove for the user's convenience in summer and the battery charged to support the alternator for eco-friendly solar power adaption. There was a fault in system structure of the existing MPPT(maximum power point tracking) method. So, to solve the fault and improve the efficiency, we have researched the modified MPPT method that is based on the load changing to control the MPPT. Through the lab and field test, the performance of proposed method is proved. Using real time control cooperated by CAN communication. The efficiency is improved more than 10% in HVAC fan operation, and car battery is also charged safely.

Antitumor effect of TW-37, a BH3 mimetic in human oral cancer

안치현,이원우,정윤찬,신지애,홍경옥,최수정,Neeti Swarup,김지훈,안민혜,정민정,진보환,조성대 한국실험동물학회 2019 Laboratory Animal Research Vol.35 No.4

TW-37 is a small molecule B cell lymphoma-2 (Bcl-2) homology 3 mimetic with potential anticancer activities. However, the in vivo anti-cancer effect of TW-37 in human oral cancer has not been properly studied yet. Here, we attempted to confirm antitumor activity of TW37 in human oral cancer. TW-37 significantly inhibited cell proliferation and increased the number of dead cells in MC-3 and HSC-3 human oral cancer cell lines. TW-37 enhanced apoptosis of both cell lines evidenced by annexin V/propidium iodide double staining, sub-G1 population analysis and the detection of cleaved poly (ADP-ribose) polymerase and caspase-3. In addition, TW-37 markedly downregulated the expression of Bcl-2 protein, while not affecting Bcl-xL or myeloid cell leukemia-1. In vivo, TW-37 inhibited tumor growth in a nude mice xenograft model without any significant liver and kidney toxicities. Collectively, these data reveal that TW-37 may be a promising small molecule to inhibit human oral cancer.

병원 내 폭력에 대한 바른 대처

안치현 대한의사협회 의료정책연구소 2017 의료정책포럼 Vol.15 No.4