me

Changwan Park

Hello! I use id pcw109550, diff, or diff72840089. You can call me diff. I build stuff in the morning/afternoon, break stuff in the evening, and make things decentralized at night.

Contact me at pcw109550 at gmail.com or at X, LinkedIn, GitHub.

Interests: Blockchain, Cryptography, Virtual Machines, Rollups

Experience

Software Engineer @ OP Labs, 2025.06 ~

• Protocol Team: OP Stack core protocol development. Public Commits
• Keywords: OP Stack

Software Engineer @ Test in Prod, 2023.3 ~ 2024.10

• Contribute to Optimism - OP Stack
  • Consensus Layer
    • Span Batch which reduces L1 Security Fees. This feature went live at Delta Hard Fork. GitHub Tracker
  • Execution Layer
    • OP-Erigon, providing efficient storage and faster sync.
  • Settlement Layer
    • Asterisc, a fault-proof VM which proves execution of a RISC-V program.
  • Infra (closed source)
• Keywords: Blockchain, OP Stack, Distributed Ledger Technology, Cryptography, k8s

Software Engineer @ Sendbird, 2021.3 ~ 2022.5

• Developed Sendbird Calls
• Keywords: Python, C++ Backend Developmen, Media Server, Load Testing, WebRTC

Intern @ Crazing Lab, 2020.3 ~ 2020.8

• Developed ML inference pipeline for autonomous robots
• Keywords: Object Detection, Pose Estimation, SLAM

Honors And Awards

HITCON CTF Finals

• 2024: Invited as a member of SuperDiceCode, ranking in 11th

DEF CON CTF Finals

• 2024: Invited as a member of SuperDiceCode, ranking in 3rd, Media
• 2023: Invited as a member of SuperDiceCode, ranking in 8th
• 2022: Invited as a member of DiceGuesser, ranking in 10th
• 2019: Invited as a member of KaisHackGoN, ranking in 12th

SECCON CTF International Division Finals

• 2023: Invited as a member of HK Guesser, ranking in 5th

CODEGATE CTF University Division Finals

• 2023: Awarded as a member of KAIST GoN, ranking in 1st(Minister of Science and ICT Award), Media
• 2022: Awarded as a member of KAIST GoN, ranking in 1st(Minister of Science and ICT Award), Media

Cyber Conflict Exercise General Division Finals

• 2023: Awarded as a member of NoG, ranking in 3rd(National Research Council of Science and Technology Director Award)

AI Cyber Defense Contest University Division Finals

• 2025: Awarded as a member of Pwngrad, ranking in 1st(Korea Information Security Industry Association Director Award), Media

Korea Crypto Analysis Contest(암호분석경진대회)

• 2024: Awarded as a leader of 염소가죽, ranking in 3rd(Defense Security Agency Commander Award)
• 2023: Awarded as a leader of 염소가죽, ranking in 2nd(Defense Intelligence Agency Director Award)
• 2022: Awarded as a leader of KAIST GoN, ranking in 1st(Minister of Defense Award), Media

Korea National Crypto Contest(국가암호공모전) Div2(Problem Solving)

• 2019: Awarded as a leader of KAIST GoN, ranking in 2nd(KISA Director Award)
• 2018: Awarded as a member of KAIST GoN, ranking in 1st(Korea NIS Director Award)
• 2017: Awarded as a leader of KAIST GoN, ranking in 3rd(Korea NSRI Director Award)

Blaz CTF

• 2024: Awarded as a member of Team KimchiPremium, ranking in 1st

Remedy CTF

• 2025: Awarded as a member of Team KimchiPremium, ranking in 3rd

Projects

CTF Writeups, 2018 ~

• Wrote 50+ CTF writeups in fields of {Cryptography, Blockchain, Reversing}

CTF Challenge Author, 2019 ~

• Wrote 20+ CTF challenges in fields of {Cryptography, Blockchain, Reversing}
• Authored CTF: CODEGATE {2020, 2024, 2025}, WACON {2022, 2023}, Whitehat {2019, 2020, 2021, 2022}

Education

KAIST, 2017 ~ Present. Currently on leave of absence.

• Undergraduate. Major: Electrical Engineering, Double Major: Computer Science

UC Santa Cruz, 2019 Summer

• Summer Session