FDXT: Forward and Backward Private Conjunctive Searchable Encryption to Suppress Volume Leakages Caused by Cross-Tags

: Li, Yuanhong; Xu, Peng; Zhang, Bochuan; Wang, Wei; Zheng, Yubo; Liang, Kaitai

Publisher: Institute of Electrical and Electronics Engineers (IEEE)

: 2026

IEEE Transactions on Information Forensics and Security

: 21

: 4432

: 4445

: 1556-6013

: 1556-6021

DOI: https://doi.org/10.1109/TIFS.2026.3687047

: https://doi.org/10.1109/tifs.2026.3687047

Dynamic Searchable Symmetric Encryption (DSSE) allows clients to update data and search keywords securely over symmetrically encrypted data on an honest but curious server. Conjunctive DSSE, an attractive type of DSSE with expressive search, enables clients to find data containing multiple keywords simultaneously. However, recently proposed efficient conjunctive DSSE schemes, such as ODXT (in NDSS’21) and SDSSE-CQ (in PETS’25), all rely on cross-tag techniques and suffer from either forward privacy or volume-privacy leakages arising from conjunctive keywords, making them vulnerable to injection or leakage-abuse attacks. In this work, we analyze the aforementioned works in depth and design a new conjunctive DSSE scheme named FDXT. For any search query with multiple keywords, FDXT guarantees the forward privacy of all queried keywords. In contrast, ODXT only maintains the forward privacy of the single and first queried keyword. FDXT also avoids volume leakage compared with SDSSE-CQ. Finally, we compared FDXT with ODXT and SDSSE-CQ in terms of performance on the Crime, Wikipedia, and Enron datasets. The experimental results show that FDXT exhibits good performance, which is comparable to ODXT and significantly better than SDSSE-CQ.

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This work was supported by the National Natural Science Foundation of China under Grant 62272186 and Grant 62372201.