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Chaochao Chen

45 accepted papers

2026

Demystifying the Optimal Fair Classifier in Multi-Class Classification

ICML 2026poster

Ensuring fair and equitable treatment across diverse groups, particularly in multi-class classification tasks, poses a significant challenge due to the persistent biases inherent in machine learning models. Most existing bias mitigation techniques are tailored to binary settings, and the presence of…

Cited by 0SourceScholar
2026

FedAU2: Attribute Unlearning for User-Level Federated Recommender Systems with Adaptive and Robust Adversarial Training

AAAI 2026technical

Federated Recommender Systems (FedRecs) leverage federated learning to protect user privacy by retaining data locally. However, user embeddings in FedRecs often encode sensitive attribute information, rendering them vulnerable to attribute inference attacks. Attribute unlearning has emerged as a pro

Cited by 0SourcePDFScholar
2026

KINGUARD: HIERARCHICAL KINSHIP-AWARE FINGERPRINTING TO DEFEND AGAINST LARGE LANGUAGE MODEL STEALING

ICASSP 2026poster

Protecting the intellectual property of large language models requires robust ownership verification. Conventional backdoor fingerprinting, however, is flawed by a stealth-robustness paradox: to be robust, these methods force models to memorize fixed responses to high-perplexity triggers, but this t…

Cited by 0SourcePDFScholar
2026

Leveraging Machine Unlearning for Cost-Efficient Preference Alignment

ICML 2026poster

Despite advances in Preference Alignment (PA) for Large Language Models (LLMs), mainstream methods like reinforcement learning with human feedback face notable challenges. These approaches require high-quality datasets of positive preference examples, which are costly to obtain and computationally i…

Cited by 0SourceScholar
2026

Potent but Stealthy: Rethink Profile Pollution Against Sequential Recommendation via Bi-Level Constrained Reinforcement Paradigm

AAAI 2026technical

Sequential Recommenders, which exploit dynamic user intents through interaction sequences, are vulnerable to adversarial attacks. While existing attacks primarily rely on data poisoning, they require large-scale user access or fake profiles thus lacking practicality. In this paper, we focus on the P

Cited by 0SourcePDFScholar
2026

Preference-Calibrated Optimization with Score-Level Distribution Alignment for Text-to-Image Diffusion Model Unlearning

ICML 2026poster

While text-to-image diffusion models achieve remarkable generation quality, they inadvertently memorize sensitive content, necessitating machine unlearning to prevent undesired outputs. However, existing unlearning methods rely on suboptimal surrogate objectives rather than directly optimizing the u…

Cited by 0SourceScholar
2026

Spiked-CFR: Causal Representation Learning from LLMs via Wasserstein Projection Pursuit

ICML 2026poster

Estimating treatment effects from observational text is increasingly practical with Large Language Models (LLMs). However, applying causal representation learning directly to high-dimensional LLM embeddings faces a fundamental barrier: empirical Wasserstein matching suffers from the curse of dimensi…

Cited by 0SourceScholar
2026

TOFA: Training-Free One-Shot Federated Adaptation for Vision-Language Models

AAAI 2026technical

Efficient and lightweight adaptation of pre-trained Vision-Language Models (VLMs) to downstream tasks through collaborative interactions between local clients and a central server is a rapidly emerging research topic in federated learning. Existing adaptation algorithms are typically trained iterati

Cited by 0SourcePDFScholar
2026

Targeting Borderline Fraudsters: Multi-View Hypergraph Fraud Detection with LLM-Guided Contrastive Learning

AAAI 2026technical

Graph fraud detection (GFD) on transaction networks is crucial for safeguarding financial systems. However, due to the limited perspective of existing graph neural networks (GNNs) in the single transaction view, sophisticated fraudsters can disguise themselves to exhibit weak fraud signals, appearin

Cited by 0SourcePDFScholar
2026

Test-Time Debiasing with Probabilistic Prompts via Wasserstein Distance in Vision-Language Models

ICML 2026poster

Vision-Language Models (VLMs) inherit social biases from large-scale pretraining data, and these biases can amplify in downstream tasks, leading to systematic performance disparities across sensitive groups. Due to the high training cost and the risk of catastrophic forgetting, recent research has f…

Cited by 0SourceScholar
2025

Controllable Unlearning for Image-to-Image Generative Models via $\epsilon$-Constrained Optimization

ICLR 2025poster

While generative models have made significant advancements in recent years, they also raise concerns such as privacy breaches and biases. Machine unlearning has emerged as a viable solution, aiming to remove specific training data, e.g., containing private information and bias, from models. In this…

Cited by 1SourcePDFScholar
2025

DR-VAE: Debiased and Representation-enhanced Variational Autoencoder for Collaborative Recommendation

AAAI 2025technical

Recommender Systems (RSs) are widely applied for navigating information, and Collaborative Filtering (CF) is one of prominent recommendation techniques due to the advantages of domain independence and easy interpretation. Among the numerous CF methods, Variational Autoencoders (VAE), benefiting from…

2025

Efficient Source-free Unlearning via Energy-Guided Data Synthesis and Discrimination-Aware Multitask Optimization

ICML 2025spotlight

With growing privacy concerns and the enforcement of data protection regulations, machine unlearning has emerged as a promising approach for removing the influence of forget data while maintaining model performance on retain data. However, most existing unlearning methods require access to the origi…

Cited by 0SourcePDFScholar
2025

FOCoOp: Enhancing Out-of-Distribution Robustness in Federated Prompt Learning for Vision-Language Models

ICML 2025poster

Federated prompt learning (FPL) for vision-language models is a powerful approach to collaboratively adapt models across distributed clients while preserving data privacy. However, existing FPL approaches suffer from a trade-off between performance and robustness, particularly in out-of-distribution…

Cited by 0SourcePDFScholar
2025

FedFACT: A Provable Framework for Controllable Group-Fairness Calibration in Federated Learning

NeurIPS 2025poster

With emerging application of Federated Learning (FL) in decision-making scenarios, it is imperative to regulate model fairness to prevent disparities across sensitive groups (e.g., female, male). Current research predominantly focuses on two concepts of group fairness within FL: *Global Fairness* (o…

Cited by 0SourceScholar
2025

FedGOG: Federated Graph Out-of-Distribution Generalization with Diffusion Data Exploration and Latent Embedding Decorrelation

AAAI 2025technical

Federated graph learning (FGL) has emerged as a promising approach to enable collaborative training of graph models while preserving data privacy. However, current FGL methods overlook the out-of-distribution (OOD) shifts that occur in real-world scenarios. The distribution shifts between training a…

Cited by 0SourcePDFScholar
2025

LoGoFair: Post-Processing for Local and Global Fairness in Federated Learning

AAAI 2025technical

Federated learning (FL) has garnered considerable interest for its capability to learn from decentralized data sources. Given the increasing application of FL in decision-making scenarios, addressing fairness issues across different sensitive groups (e.g., female, male) in FL is crucial. Current res…

2025

Sim4Rec: Data-Free Model Extraction Attack on Sequential Recommendation

AAAI 2025technical

Model extraction attack shows promising performance in revealing sequential recommendation (SeqRec) robustness, e.g., as an upstream task of transfer-based attack to provide optimization feedback for downstream attacks. However, existing work either heavily relies on impractical prior knowledge or h…

Cited by 0SourcePDFScholar
2025

UMU-Bench: Closing the Modality Gap in Multimodal Unlearning Evaluation

NeurIPS 2025poster

Although Multimodal Large Language Models (MLLMs) have advanced numerous fields, their training on extensive multimodal datasets introduces significant privacy concerns, prompting the necessity for efficient unlearning methods. However, current multimodal unlearning approaches often directly adapt t…

Cited by 7SourceScholar
2024

CURE4Rec: A Benchmark for Recommendation Unlearning with Deeper Influence

NeurIPS 2024poster

With increasing privacy concerns in artificial intelligence, regulations have mandated the right to be forgotten, granting individuals the right to withdraw their data from models. Machine unlearning has emerged as a potential solution to enable selective forgetting in models, particularly in recomm…

2024

FOOGD: Federated Collaboration for Both Out-of-distribution Generalization and Detection

NeurIPS 2024poster

Federated learning (FL) is a promising machine learning paradigm that collaborates with client models to capture global knowledge. However, deploying FL models in real-world scenarios remains unreliable due to the coexistence of in-distribution data and unexpected out-of-distribution (OOD) data, suc…

2024

Federated Graph Learning for Cross-Domain Recommendation

NeurIPS 2024poster

Cross-domain recommendation (CDR) offers a promising solution to the data sparsity problem by enabling knowledge transfer across source and target domains. However, many recent CDR models overlook crucial issues such as privacy as well as the risk of negative transfer (which negatively impact model…

Cited by 2SourcePDFScholar
2024

Fine-grained Pluggable Gradient Ascent for Knowledge Unlearning in Language Models

EMNLP 2024main

Pre-trained language models acquire knowledge from vast amounts of text data, which can inadvertently contain sensitive information. To mitigate the presence of undesirable knowledge, the task of knowledge unlearning becomes crucial for language models. Previous research relies on gradient ascent me…

2024

Intra- and Inter-group Optimal Transport for User-Oriented Fairness in Recommender Systems

AAAI 2024technical

Recommender systems are typically biased toward a small group of users, leading to severe unfairness in recommendation performance, i.e., User-Oriented Fairness (UOF) issue. Existing research on UOF exhibits notable limitations in two phases of recommendation models. In the training phase, current m…

Cited by 6SourcePDFScholar
2024

Learning Accurate and Bidirectional Transformation via Dynamic Embedding Transportation for Cross-Domain Recommendation

AAAI 2024technical

With the rapid development of Internet and Web techniques, Cross-Domain Recommendation (CDR) models have been widely explored for resolving the data-sparsity and cold-start problem. Meanwhile, most CDR models should utilize explicit domain-shareable information (e.g., overlapped users or items) for…

Cited by 24SourcePDFScholar
2024

One for All: A Universal Generator for Concept Unlearnability via Multi-Modal Alignment

ICML 2024poster

The abundance of free internet data offers unprecedented opportunities for researchers and developers, but it also poses privacy risks. Utilizing data without explicit consent raises critical challenges in protecting personal information.Unlearnable examples have emerged as a feasible protection app…

Cited by 3SourcePDFScholar
2024

Protecting Split Learning by Potential Energy Loss

IJCAI 2024poster

As a practical privacy-preserving learning method, split learning has drawn much attention in academia and industry. However, its security is constantly being questioned since the intermediate results are shared during training and inference. In this paper, we focus on the privacy leakage from the f…

Cited by 0SourcePDFScholar
2024

Reducing Item Discrepancy via Differentially Private Robust Embedding Alignment for Privacy-Preserving Cross Domain Recommendation

ICML 2024poster

Cross-Domain Recommendation (CDR) have become increasingly appealing by leveraging useful information to tackle the data sparsity problem across domains. Most of latest CDR models assume that domain-shareable user-item information (e.g., rating and review on overlapped users or items) are accessible…

Cited by 7SourcePDFScholar
2024

Rethinking the Representation in Federated Unsupervised Learning with Non-IID Data

CVPR 2024poster

Federated learning achieves effective performance in modeling decentralized data. In practice client data are not well-labeled which makes it potential for federated unsupervised learning (FUSL) with non-IID data. However the performance of existing FUSL methods suffers from insufficient representat…

Cited by 17SourcePDFScholar
2024

UKnow: A Unified Knowledge Protocol with Multimodal Knowledge Graph Datasets for Reasoning and Vision-Language Pre-Training

NeurIPS 2024poster

This work presents a unified knowledge protocol, called UKnow, which facilitates knowledge-based studies from the perspective of data. Particularly focusing on visual and linguistic modalities, we categorize data knowledge into five unit types, namely, in-image, in-text, cross-image, cross-text, and…

Cited by 0SourcePDFScholar
2023

Federated Probabilistic Preference Distribution Modelling with Compactness Co-Clustering for Privacy-Preserving Multi-Domain Recommendation

IJCAI 2023poster

With the development of modern internet techniques, Cross-Domain Recommendation (CDR) systems have been widely exploited for tackling the data-sparsity problem. Meanwhile most current CDR models assume that user-item interactions are accessible across different domains. However, such knowledge shari…

Cited by 35SourcePDFScholar
2023

HyperFed: Hyperbolic Prototypes Exploration with Consistent Aggregation for Non-IID Data in Federated Learning

IJCAI 2023poster

Federated learning (FL) collaboratively models user data in a decentralized way. However, in the real world, non-identical and independent data distributions (non-IID) among clients hinder the performance of FL due to three issues, i.e., (1) the class statistics shifting, (2) the insufficient hierar…

Cited by 18SourcePDFScholar
2023

PPGenCDR: A Stable and Robust Framework for Privacy-Preserving Cross-Domain Recommendation

AAAI 2023technical

Privacy-preserving cross-domain recommendation (PPCDR) refers to preserving the privacy of users when transferring the knowledge from source domain to target domain for better performance, which is vital for the long-term development of recommender systems. Existing work on cross-domain recommendati…

Cited by 28SourcePDFScholar
2023

Reducing Communication for Split Learning by Randomized Top-k Sparsification

IJCAI 2023poster

Split learning is a simple solution for Vertical Federated Learning (VFL), which has drawn substantial attention in both research and application due to its simplicity and efficiency. However, communication efficiency is still a crucial issue for split learning. In this paper, we investigate multipl…

Cited by 12SourcePDFScholar
2023

Robust Representation Learning with Reliable Pseudo-labels Generation via Self-Adaptive Optimal Transport for Short Text Clustering

ACL 2023long

Short text clustering is challenging since it takes imbalanced and noisy data as inputs. Existing approaches cannot solve this problem well, since (1) they are prone to obtain degenerate solutions especially on heavy imbalanced datasets, and (2) they are vulnerable to noises. To tackle the above iss…

2023

UltraRE: Enhancing RecEraser for Recommendation Unlearning via Error Decomposition

NeurIPS 2023poster

With growing concerns regarding privacy in machine learning models, regulations have committed to granting individuals the right to be forgotten while mandating companies to develop non-discriminatory machine learning systems, thereby fueling the study of the machine unlearning problem. Our attentio…

2022

HCFRec: Hash Collaborative Filtering via Normalized Flow with Structural Consensus for Efficient Recommendation

IJCAI 2022poster

The ever-increasing data scale of user-item interactions makes it challenging for an effective and efficient recommender system. Recently, hash-based collaborative filtering (Hash-CF) approaches employ efficient Hamming distance of learned binary representations of users and items to accelerate reco…

2022

Vertically Federated Graph Neural Network for Privacy-Preserving Node Classification

IJCAI 2022poster

Recently, Graph Neural Network (GNN) has achieved remarkable progresses in various real-world tasks on graph data, consisting of node features and the adjacent information between different nodes. High-performance GNN models always depend on both rich features and complete edge information in graph.…

Cited by 132SourcePDFScholar
2021

Cross-Domain Recommendation: Challenges, Progress, and Prospects

IJCAI 2021poster

To address the long-standing data sparsity problem in recommender systems (RSs), cross-domain recommendation (CDR) has been proposed to leverage the relatively richer information from a richer domain to improve the recommendation performance in a sparser domain. Although CDR has been extensively stu…

2021

Exploiting Data Sparsity in Secure Cross-Platform Social Recommendation

NeurIPS 2021poster

Social recommendation has shown promising improvements over traditional systems since it leverages social correlation data as an additional input. Most existing work assumes that all data are available to the recommendation platform. However, in practice, user-item interaction data (e.g.,rating) and…

Cited by 44SourcePDFScholar
2021

Leveraging Distribution Alignment via Stein Path for Cross-Domain Cold-Start Recommendation

NeurIPS 2021poster

Cross-Domain Recommendation (CDR) has been popularly studied to utilize different domain knowledge to solve the cold-start problem in recommender systems. In this paper, we focus on the Cross-Domain Cold-Start Recommendation (CDCSR) problem. That is, how to leverage the information from a source dom…

Cited by 72SourcePDFScholar
2020

A Graphical and Attentional Framework for Dual-Target Cross-Domain Recommendation

IJCAI 2020poster

The conventional single-target Cross-Domain Recommendation (CDR) only improves the recommendation accuracy on a target domain with the help of a source domain (with relatively richer information). In contrast, the novel dual-target CDR has been proposed to improve the recommendation accuracies on bo…

Cited by 0SourcePDFScholar
2019

Generalization in Generative Adversarial Networks: A Novel Perspective from Privacy Protection

NeurIPS 2019poster

In this paper, we aim to understand the generalization properties of generative adversarial networks (GANs) from a new perspective of privacy protection. Theoretically, we prove that a differentially private learning algorithm used for training the GAN does not overfit to a certain degree, i.e., the…

Cited by 57SourcePDFScholar