Experience

Security Engineer, Flatt Security Inc. Tokyo, Japan	May 2020 - PRESENT 1y 8 months
» Finding vulnerabilities in client's softwares and websites. » 0day research, pentests, etc.

Security Engineer, LINE Corporation Tokyo, Japan	Feb 2019 - Apr 2020 1y 3 months
» Mainly focused on finding vulnerabilities in LINE and its affiliates' products. » Developed automated security analysis tools and tools for detecting potential risks. » Security consulting, Reviewing bugbounty reports, recruitment support, etc.

Security Researcher, SEWorks Inc. Seoul, South Korea	June 2014 - Nov 2018 4y 5 months
» Focused mainly on core server management and backend service development. » Developed core products, including product maintanence. (Used python, GoLang+Redis, PHP, Java, etc.) » Frequently performed vulnerability checks and penetration tests on flagship products. » Focused on security researches for future developments.

Signaller, ROK Army Paju, South Korea	Nov 2016 - Aug 2018 1y 8 months
» Discharged as Sergeant. Received many awards while working in the army. » Maintained internal systems, managed and monitored security firewalls. » Developed an application which automatically checks security status and prints out the report on every boot. » Developed a pentest software to increase awareness on side-effects of using smartphones in the army.

Education

Undergraduate Student, University of Toronto	Sept. 2014 - June 2015 9 months
» Currently studying as an undergraduate, and is going to acquire a Bachelor’s degree at some point. » Currently on a long leave for jobs.

International Baccalaureate Diploma	Sept. 2012 - June 2014 1y 9 months
» Acquired International Baccalaureate Diploma for Secondary School. » Studied in India

International
2021	2nd place, N1CTF 2021	Online
2021	Finalist, DEFCON 29 CTF	Online
2021	2nd place, LINE CTF	Online
2019	1st place, Hack.lu CTF	Germany
2019	1st place, Harekaze CTF	Japan
2019	Finalist, DEFCON 27 CTF	United States
2019	1st place, 0CTF 2019	China
2018	Finalist, Real World CTF 2018	China
2017	Finalist, CodeGate CTF 2017	South Korea
2016	2nd place, EKOPARTY CTF 2016	Argentina
2016	2nd place, Silk Road CTF 2016	China
2016	1st place, ASIS CTF 2016 Finals	Iran
2016	1st place, C4CTF 2016	Saudi Arabia
2016	1st place, TU CTF 2016	United States
2016	1st place, Sharif University CTF	Iran
2016	2nd place, Internetwache CTF	Germany
2016	Finalist, PHDays 2016	Russia
2015	1st place, Hack Zone Tunisia 2015	Tunisia
2015	1st place, Break In 2015	India
2015	Finalist, CSAW CTF 15	United States
2014	Finalist, CSAW CTF 14	United States
2014	Finalist, DEFCON 22 CTF	United States
2014	2nd place. Olympic Sochi CTF 2015	Russia

Domestic
2019	1st place, Cyber Operations Challenge (Whitehat Contest)	Seoul, South Korea
2018	1st place, Korean Army Hacking Defense Contest	Daejeon, South Korea
2015	1st place, 14th HUST Hacking Festival	Seoul, South Korea
2015	1st place, 2015 Inc0gnito Hacking Competition	Seoul, South Korea

» Please feel free to contact me for any writeups that I've not published

CTF Organizer and Security Challenge Author

2014 - PRESENT

2019	Author, babypress and lfi2019, XCTF Finals 2019.
2018	Author, moehost and gameshop, ASISCTF 2018 Quals. Writeups are available here.
2014-2016	Organizer and challenge author, KAIST and POSTECH Science War (Hacking)
	» Some of challenged released in the Science War can now be played on Stereotyped Challenges

Stereotyped Challenges	Oct. 2014 - PRESENT 7y 3 months
//chall.stypr.com » Operating and developing a website consisting of extremely technical offensive security challenges. » Most of challenges are solely developed and tested by me. all challenges are sandboxed seperately. » Sourcecode of the website is currently available on //github.com/stypr/chall.stypr.com

Web Fuzzer Development and its Utilization	June 2014
Talked on WOWHACKER 2^nd Seminar. Seoul, Korea » a.k.a. Introduction to web fuzzer development. » Demonstrated the process of web fuzzer development and its utilization, including the practical usage of fuzzers and its utilizations.

Apparatus and method for managing apk file in a android platform	May 2016
Patent ID: KR101623096B1, 5 inventors » The present invention provides an apparatus for managing APK file in an android platform configured to prevent an executable file in an APK file from being analyzed through reverse engineering and decompilation in advance

Language	PHP (Native), Python (Native), SQL (Native), VB (Mediocre), C (Mediocre), Go (Mediocre), Java (Mediocre), ASM (Beginner)
	Korean (Native), English (Native), Mandarin (Beginner), Japanese (Beginner)
Softwares	WireShark, Chrome/Firefox devtools, WireShark, Hex-rays, My Own Fuzzer, x64dbg, NetCat, Fiddler
	HeidiSQL, HxD, Git, VMWare, qemu, ESXi, etc.