Hello, this is

Zhangchen Xu .


I am a second-year PhD student at Network Security Lab at the University of Washington, Seattle, advised by Prof. Radha Poovendran. Prior joining UW, I received my bachelor’s (joint) degree in Communication Engineering at University of Electronic Science and Technology of China (UESTC) and University of Glasgow (UofG). During my undergrad, I was advised by Prof. Lei Zhang.

My email -> zxu9 [at] uw [dot] edu

[Upcoming Travel] USENIX Security 2024, Philadelphia, August 14-16.

Research Interests

My research interests lie broadly in security, privacy and fairness of machine learning, with a current emphasis on the safety and alignment of large language models (LLMs). I am working with a group of amazing collaborators in the following topics:

  • LLM Safety. I investigate emerging security threats in LLMs and explore defense mechanisms. My particular interest lies in inference-time defenses, including: SafeDecoding (for jailbreaking), CleanGen (for backdoor), Shield (for LLM-integrated Apps).
  • LLM (Open) Alignment. I explore the science behind LLM alignment to make LLMs more helpful and better align with human values. I developed Magpie datasets & models.
  • Federated Learning. Security, privacy and fairness in large-scale Federated Learning systems: ACE, Brave.

During my undergraduate, my research focus was the theory and algorithm of distributed consensus: Voting Validity, Wireless Distributed Consensus.

Selected Work (see here for full publication list)

Magpie: Alignment Data Synthesis from Scratch by Prompting Aligned LLMs with Nothing

Zhangchen Xu, Fengqing Jiang, Luyao Niu, Yuntian Deng, Radha Poovendran, Yejin Choi, Bill Yuchen Lin

Arxiv | Paper / website / Huggingface / Code / Demo

ACE: A Model Poisoning Attack on Contribution Evaluation Methods in Federated Learning

Zhangchen Xu, Fengqing Jiang, Luyao Niu, Jinyuan Jia, Bo Li, Radha Poovendran

Usenix Security 2024 | Paper

SafeDecoding: Defending against Jailbreak Attacks via Safety-Aware Decoding

Zhangchen Xu, Fengqing Jiang, Luyao Niu, Jinyuan Jia, Bill Yuchen Lin, Radha Poovendran

ACL 2024 (Main) | Paper / Code / Poster

ArtPrompt: ASCII Art-based Jailbreak Attacks against Aligned LLMs

Fengqing Jiang*, Zhangchen Xu*, Luyao Niu*, Zhen Xiang, Bhaskar Ramasubramanian, Bo Li, Radha Poovendran

ACL 2024 (Main) | Paper / Code / Poster

Exact Fault-Tolerant Consensus with Voting Validity

Zhangchen Xu, Yuetai Li, Chenglin Feng, Lei Zhang

IPDPS 2023 (Oral Presentation) | Paper / Slides