OnChainSE: Verifiable Encrypted Search Over Blockchain Data for JointCloud Environments

Abstract

JointCloud computing enables multiple cloud domains to collaboratively process and share data across organizational boundaries. In such settings, sensitive data are distributed among mutually distrustful participants and require strong protection during storage and retrieval. Blockchain offers a decentralized trust foundation for JointCloud systems through tamperevident logging and coordinated data management, yet efficient search over encrypted on-chain records remains insufficiently supported. Existing authenticated blockchain query structures are largely designed for plaintext predicates, whereas searchableencryption solutions typically rely on off-chain indexes or hybrid execution, which may enlarge the trust boundary and complicate result verification. This paper presents OnChainSE, a blockchain-native architecture for verifiable search over encrypted blockchain data in JointCloud environments. Unlike conventional authenticated query frameworks for plaintext attributes, OnChainSE targets settings in which both searchable attributes and query inputs must remain protected across collaborating cloud domains. It integrates encrypted keywords, encrypted numerical metadata, and authenticated index commitments into a unified blockchainnative structure to support privacy-preserving keyword and range queries. It further enables succinct per-block verification through proof aggregation, allowing lightweight clients to validate the authenticity of returned encrypted pointers and check their consistency with committed on-chain search state without reconstructing the full search state. Compact checkpoint summaries are also introduced to narrow the search scope and reduce historical retrieval overhead before proof generation. We implement an OnChainSE prototype and evaluate it under diverse data scales and query workloads. Experimental results show that OnChainSE reduces query overhead and proof cost under the evaluated workloads while preserving verifiable retrieval for encrypted data. These results suggest that OnChainSE is a practical approach to authenticated encrypted retrieval in blockchain-enabled JointCloud systems.