NSHEDB: Noise-Sensitive Homomorphic Encrypted Database Query Engine
2026-02-27 • Databases
DatabasesCryptography and Security
AI summaryⓘ
The authors designed NSHEDB, a system that allows encrypted data to be queried securely without needing to decrypt it first, using a type of encryption called homomorphic encryption. Their system reduces the usual big increase in data size and avoids expensive reset steps, making computations like comparing data and summing values more practical. NSHEDB also plans queries carefully to keep the encryption secure while doing deeper computations. When tested, it was much faster and used much less storage than previous similar systems, all while maintaining strong security without needing trusted hardware or sharing secret keys.
homomorphic encryptionleveled homomorphic encryption (LHE)BFV schemeciphertext expansionbootstrappingsecure query processingnoise managementTPC-H benchmarksemi-honest modelcryptographic security
Authors
Boram Jung, Yuliang Li, Hung-Wei Tseng
Abstract
Homomorphic encryption (HE) enables computations directly on encrypted data, offering strong cryptographic guarantees for secure and privacy-preserving data storage and query execution. However, despite its theoretical power, practical adoption of HE in database systems remains limited due to extreme cipher-text expansion, memory overhead, and the computational cost of bootstrapping, which resets noise levels for correctness. This paper presents NSHEDB, a secure query processing engine designed to address these challenges at the system architecture level. NSHEDB uses word-level leveled HE (LHE) based on the BFV scheme to minimize ciphertext expansion and avoid costly bootstrapping. It introduces novel techniques for executing equality, range, and aggregation operations using purely homomorphic computation, without transciphering between different HE schemes (e.g., CKKS/BFV/TFHE) or relying on trusted hardware. Additionally, it incorporates a noise-aware query planner to extend computation depth while preserving security guarantees. We implement and evaluate NSHEDB on real-world database workloads (TPC-H) and show that it achieves 20x-V1370x speedup and a 73x storage reduction compared to state-of-the-art HE-based systems, while upholding 128-bit security in a semi-honest model with no key release or trusted components.