Paper 2025/887

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

Abstract

A decentralized storage network (DSN) enables clients to delegate data to servers, where the data must be retained custody for a jointly agreed contract period. Most existing constructions employ proof-of-replication (PoRep) iteratively to provide verifiable guarantees during this period. However, the original PoRep security model does not account for iterative invocation, particularly when aided by a blockchain that serves as an external repository of auxiliary information. Similar concerns arise for another key DSN functionality, i.e., data retrieval, where malicious parties may exploit previous and parallel sessions to undermine fairness. This work addresses these gaps by formalizing the syntax and adaptive security of blockchain-aided DSN protocols, presenting, to the best of our knowledge, the first formal treatment. Building on this foundation, we propose a generic construction that leverages an Extended UTxO (EUTxO) ledger, automating protocol execution by embedding the required verification into EUTxO's validation logic. We further prove that the succinctness and non-malleability of the underlying proof system suffice for adaptive security. Our experiments corroborate this: systems lacking these properties are vulnerable to adaptive attacks, e.g., servers offloading storage while still producing valid PoRep proofs.