Paper 2025/887

Adaptively Secure Blockchain-Aided Decentralized Storage Networks: Formalization and Generic Construction

Abstract

Blockchain-aided decentralized storage networks (DSNs) use public audits to verify outsourced storage and smart contracts to govern payments and collateral. Published audit evidence, however, remains available to servers and may let them reduce local storage while continuing to pass audits. Retrieval must also remain fair across adaptively selected sessions. We formalize DSN protocols across delegation, preservation, and retrieval, accounting for evolving server state and externally available proofs. To support adaptive replication soundness, we reformulate rational replication for proofs of replication (PoRep) as an extractor-based notion. We then give a generic construction combining PoRep, verifiable delay functions, and simulation-extractable zkSNARKs, with encrypted delivery and conditional authorization for retrieval. Our analysis identifies roles for succinctness and simulation-extractability beyond privacy and efficiency. Under the knowledge of strong compression assumption and the stated primitive and timing assumptions, we establish adaptive replication soundness subject to bounds on extraction resources and the cumulative public transcript. We also establish contract unforgeability and retrieval fairness. Controlled experiments illustrate storage offloading through public audit evidence, while a separate Merkle-PLONK prototype measures proving and verification costs through Cardano's Plutus interface.