Summer 2025 — Google Ads Privacy and Data Governance (APDG)
Built data and interactive feedback pipelines to automate privacy documentation writing and review processes using experimental fine-tuned Gemini APIs.
About Me
I'm an undergraduate student in Theoretical CS at Columbia University, graduating May 2026, with exposure to math and physics as well.
I'm broadly interested in anything theory-related. As of now, I'm actively thinking about:
- Individualized differential privacy with data, query, and budget adaptivities.
- Average-case complexity and smoothed analysis of total search problems.
Fundamentally, I'm driven by privacy — the pursuit of "the right to be let alone". My interests in cryptography, privacy, and the theoretical foundations of related fields are instantiations of this fundamental drive.
Contact
Email: yc3879@columbia.edu
GitHub: mychern
Google Scholar: link
Research
By default, authors are ordered alphabetically by last name. * indicates co-authors who contributed equally (also alphabetically listed).
Publications & Preprints
- A follow-up to the SOSP '24 paper Cookie Monster.
- At the CS3 NSF site visit day workshop, our work received unanimous top-band rating.
- PATWG preliminarily approved adopting this work to their standardization, considered by major browsers including Firefox and Chrome.
- Accepted with two “Strong Accept”s.
Talks & Posters
- [Big Bird] Evaluating Optimization Queries: Methodology and Preliminary Results [PATWG issue, slides]
- [Ind. Sparse Vector via Target Charging] Adaptive Individual Accounting with Target Charging [poster]
- [Big Bird & CityOS] Privacy-Preserving Architecture: From W3C Standards to Smart Cities [poster]
- [Average-Case Hardness of TFNP in ROM] Proof of Sequential Work / Verifiable Delay Functions in ROM [typed, written]
Survey Papers & Class Projects
- (Spring 2025) Proof Complexity. “Equivalences between TFNPdt and Low-Level Proof Systems with an example in \(\mathbb{F}_2\)-Nullstellensatz” [pdf]
- (Spring 2024) Unconditional Lower Bounds & Derandomization. “Fractional Pseudorandom Generators and Bounded Fourier Tails: A Literature Review” [pdf]
- (Spring 2024) Unconditional Lower Bounds & Derandomization. “Bounding Threshold Formulas using Multiparty Communication Complexity Techniques” [pdf]
- (Spring 2024) Advanced Cryptography. “Path to a New Secure Reinforcement Learning Model — Explicit Construction as an IP and Cryptographic Implications” [pdf]
Teaching
Teaching Assistant
Duties include weekly office hours, grading, and occasionally contributing homework or exam questions.
TA
Spring 2026
Intro to Cryptography (COMS 3262)
Columbia University — expected enrollment: 30+ students
TA
Spring 2026
Analysis of Algorithms (CSOR 4231)
Columbia University — final enrollment: 130+ students
TA
Fall 2023
Introduction to Computational Complexity (COMS 4236)
Columbia University — final enrollment: 30+ students
TA
Fall 2023
Analysis of Algorithms (CSOR 4231)
Columbia University — final enrollment: 110+ students
Seminars & Talks Given
- (Fall 2025) A Tasting of Interactive Proof Systems — notes coming soon.
- (Spring 2025) Property Testing — notes coming soon.
- (Summer 2024) Differential Privacy — 6 talks based on Prof. Gautam Kamath's course.
- (Spring 2024) Quantum Complexity Theory — talk 1 (definitions & overview), talk 6 on QMA and Local Hamiltonian Problems (with Andrew Yang). Co-organized semester-long seminar with the Columbia Undergraduate Learning Seminar in TCS.
- (Spring 2024) Cryptography ∩ TFNP — “The Journey from NP to TFNP Hardness” (with Akshat Yaparla); “Cryptographic Hardness of Finding Nash Equilibrium” (with Yizhi Huang).
- (Spring 2024) Quantum Information Theory — two-hour talk from interactive proof systems to quantum cryptography.
Typed Notes & Scribing
- (Spring 2024) COMS 6998 Unconditional Lower Bounds and Derandomization — week 5 (Håstad's Switching Lemma & \(\mathbb{F}_2\) Polynomials), week 8 (Fourier Analysis, Sandwiching Approximator & Viola's Theorem)
- (Spring 2024) MATH 3952 Undergraduate Math Seminar (Quantum Information Theory) — full scribe notes
- (Spring 2024) COMS 6261 Advanced Cryptography (TFNP) — presentation
Programs
- CS3 Summer High School Program — Why and how Cookie Monster tackles the ads attribution problem?
- Columbia Math Directed Reading Program
Industry
Google
4× intern
Summer 2024 — YouTube Nitrate Pay-Gated Content Recommendation
Data pipeline construction and fine-tuning ML models for content recommendations.
Summer 2023 — Over-the-Top (OTT) Platform Service
Wrote an end-to-end DVR testing system for streaming services, reducing bug detection time from days to hours.
Summer 2022 — YouTube Commerce Payments Backend
Wrote RPC server features for non-recurring plan listing and fulfillment.
VC / Finance
2020–2021
Gap year working on tech-focused early-stage investments
At Nantucket (Summer 2021), ZhenFund (Spring 2021), K2VC (Fall 2020), and Ivy Capital (Summer 2020). Besides managerial and investment analytical experiences, I built a portfolio management visualization tool (JavaScript) and a market research scraper (Python).
Recognitions
College
- Putnam Competition — Score of 21, ranked ~769 (2023)
- Google MLthon (for interns) Finalist
- Tau Beta Pi Inductee — Top 15% of the graduating engineering class
High School
- Regeneron Science Talent Search 2020 Scholar [arXiv]
- Shing-Tung Yau High School Science Awards — North America Regional 1st Prize; Global Honorable Mention (Top 10) in CS, 2018 [arXiv]
- Michigan SEFMD, 2019 — State Second Prize in Engineering; First in Engineering Mechanics Category [arXiv]
- Michigan SEFMD, 2018 — Category Honorable Mention [JBiSE]
- AIME Qualifier
- Johns Hopkins Hodson Trust Scholar (for top 20 first-year undergrad admits) — $156,000 scholarship over four years
- UPenn Ben Franklin Scholar (for top first-year undergrad admits)
Misc
My role model is Alex Honnold. My favorite moment of his — that is the sheer obsession I want to have.
I spent two summers in high school painting and drawing and still do casual sketches. I play basketball and tennis for fun, enjoy walking around, getting coffee and boba.
My great grandfather was a Chinese history scholar who survived the Laogai through decades of hiding. I always remember him as a knowledgeable, positive man surrounded by books from his scholarly days in the 1930s–40s. His memory lives on in my habit of reading Wikipedia pages about Chinese history and digital records of ancient texts (through this great effort!). For trivia, I can match most Gregorian years to their corresponding Chinese era names.
Originally from Ningbo, I've lived in Shanghai and Beijing (China), Manchester / Auburn NH, Bloomfield Hills MI, New York City, and the SF Bay Area. I also studied briefly in Auckland, New Zealand and Paris, France.
I'm fluent in English and Mandarin, took Latin to AP level, and am currently learning French and Russian.
Relevant Coursework
Undergrad
CS — Theory: Advanced Cryptography (intersecting TFNP), Intro to Cryptography, Unconditional Lower Bounds & Derandomization, Computational Complexity, Analysis of Algorithms, Quantum Computing.
CS — Systems: Distributed Systems, Computer Networks, Competitive Programming, Blockchain, Databases, Systems Programming, Data Structures.
Mathematics: Modern Analysis I&II, Modern Algebra I&II, Functions of Complex Variables, Topology.
Physics: Accelerated Intro to Physics I&II (Kleppner & Kolenkow for Mechanics; Purcell & Morin for E&M; quantum mechanics via A. P. French).