Privacy-Enhanced Prototype-Based Federated Cross-Modal Hashing for Cross-Modal Retrieval

Cross-modal hashing is widely used for efficient similarity searches, improving data processing efficiency, and reducing storage costs. Existing cross-modal hashing methods primarily focus on centralized training scenarios, where fixed-scale and fixed-category multi-modal data is collected beforehand. However, these methods often face challenges associated with the potential risk of privacy breaches and high data communication costs during data transmission in real-world multimedia retrieval tasks. To tackle these challenges, in this article, we propose an efficient privacy-enhanced prototype-based federated cross-modal hashing (PEPFCH). In PEPFCH, we integrate local and global prototypes in order to effectively capture the distinctive traits of individual clients, while also harnessing the collective intelligence of the entire federated learning system. Moreover, to ensure the security of prototype information and prevent its disclosure during the aggregation process, we use a prototype encryption transmission mechanism to encrypt the prototype information before transmission, making it challenging for attackers to gain access to sensitive data. Additionally, to facilitate personalized federated learning and alleviate the issue of parametric catastrophic forgetting, we establish the image and text hyper-networks for each client and adopt a hyper-network extension strategy to selectively preserve and update previously acquired knowledge when acquiring new concepts or categories. Comprehensive experiments highlight the efficiency and superiority of our proposed method. To enhance research and accessibility, we have publicly released our source codes at: https://github.com/vindahi/PEPFCH .