Bo Li

Searchable Symmetric Encryption (SSE) has emerged as a practical technology to address the low-cost data outsourcing solution accompanying the growing data privacy concerns. In the pursuit of real-world deployment, researchers have emphasized the importance of supporting Boolean queries in SSE schemes. However, existing schemes struggle to handle large-scale data due to high storage overhead and poor locality in I/O. In response to this challenge, we design a two-level block index construction for locality optimization and propose an efficient Dynamic SSE scheme with trusted hardware support, satisfying locality-based backward security that are first introduced in this paper. We evaluate its performance on datasets up to billion-scale. Our encrypted index occupies only 16.1% of the size of plaintext dataset, which is 27.0×, 21.9×, and 11.4× smaller than conventional OXT and SGX-based BISEN, POSUP schemes, respectively, while index generation is 1612.7×, 22.5×, and 7.3× faster. Most queries achieve subsecond latency, incurring no more than 25% additional overhead compared to the full-text search engine ElasticSearch. To our best knowledge, it is the first practical SSE scheme which has achieved sub-second response time on disk-based index with minimal storage overhead.

Redactable blockchains preserve the integrity of hash links while enabling authorized redactions to comply with regulatory requirements. However, existing permissioned solutions suffer from three severe issues. First, fine-grained privilege control incurs significant storage overhead, especially in the case of single-use authorization. Second, the reliance on bilinear pairings in chameleon hash leads to significant performance degradation when handling large-scale redaction requests. Finally, multiple incorporated components often unconsciously introduce centralized entities, undermining the decentralized nature. In this paper, we propose MithrilRB, a resource-efficient and decentralized redactable blockchain with single-use authorization. Specifically, we introduce a privilege control mechanism with our proposed multi-authority attribute-based signature (MA-ABS) and the threshold BLS signature, achieving fine-grained single-use authorization and direct user revocation without extra ciphertext storage. We also design a pairing-free non-interactive threshold chameleon hash (PNITCH), which enhances efficiency and is better suited for large-scale redaction requests. Moreover, MithrilRB eliminates centralized trust points that hold secret information, ensuring fully decentralization-compatible functional integration in redactable blockchains. Finally, we implement MithrilRB, and the experimental results demonstrate that MithrilRB significantly outperforms existing solutions in both computational efficiency and storage requirements.