Outsourced Secure Cross-Modal Retrieval Based on Secret Sharing for Lightweight Clients

Cross-modal retrieval is a technique that uses one modality to query another modality in multimedia data (e.g., retrieving images based on text, or retrieving text based on images). It can break down the barriers between different modalities and achieve seamless information connection. Secure cross-modal retrieval (SCMR) focuses on privacy issues in cross-modal retrieval, including private data of data owners (DOs) and private query requests of users. Current work on SCMR protects private information through homomorphic encryption, which makes the efficiency of the retrieval phase not ideal. Therefore, the conflict between retrieval efficiency and security has become an important issue that needs to be resolved in SCMR. We propose a scheme to achieve SCMR in the form of secret sharing in the IoT environment. In the scheme, the DO can secretly divide all the original data into two parts and upload them to two noncollusive cloud servers, respectively. The servers store the data and provide cross-modal retrieval for users. The security of the scheme is proved under semi-honest model, and the experiments show that our scheme is more efficient than previous work in the search phase. When the query dimension is 512 and the number of latent factors is 500, the search time is reduced by more than half compared with previous work.