Private Reachability Queries on Structured Encrypted Temporal Bipartite Graphs

A temporal bipartite graph is a graph model that incorporates time-related information into its edges, making it suitable for modeling real-world phenomena like disease outbreaks. However, this temporal information is often sensitive. To protect the privacy of graph data, researchers have explored various approaches to preserve privacy in graph queries, with reachability queries being popular and fundamental as they determine the possibility of reaching one node from others in a graph. While privacy-preserving reachability queries have been extensively studied, existing efforts often overlook the valuable attribute information present in both edges and nodes of the graphs. Moreover, reachability queries on temporal bipartite graphs have not received sufficient attention in the literature. To bridge this gap, we propose a novel approach to achieve various private r eachability q ueries on s tructured encrypted t emporal b ipartite g raphs ({\sf RQ}-{\sf STBG}) through a real-world scenario. Specifically, we construct a minimal index using hierarchical 2-hop labels and integrate structured encryption, order-revealing encryption, and garbled Bloom filters to support reachability queries with different label constraints. The proposed scheme is flexible and can cater to the query requirements of diverse users. Security analysis and experimental evaluations demonstrate that the proposed scheme achieves both preferable security and efficiency.