Origami Store: UC-Secure Foldable Datachains for the Quantum Era

Traditional blockchains preserve everything, if verification is to avoid trusted third parties. The accumulation of outdated but undeletable data makes traditional blockchains non-scalable for practical applications. Stateless blockchains mitigate this problem via history deletion; however, existing stateless blockchains such as Mimblewimble are not quantum resistant as they rely on specific discrete-log-based cryptography to achieve history deletion. In this paper, we introduce the “Origami Store” (or O-store for short), as a general new approach to distributed data storage with a generic history deletion mechanism called “folding.” O-store is built using a hash function and an arbitrary signature scheme. Since the signature scheme is decoupled from the framework, O-stores are compatible with any quantum-resistant signature scheme by design. More importantly, O-store only needs to preserve one signature and one verification key per account (or owner) for any number of transactions (or updates), thereby mitigating the inefficiency of large quantum-safe signatures and verification keys. We prove the security of the basic O-store using the framework of Universal Composability (UC); in particular, O-store's universal security is shown to hold for a generic consensus mechanism, to facilitate implementation from a wide range of decentralized consensus protocols. The Origami store is thus the first UC-secure efficient distributed data storage framework that supports plug-and-play consensus mechanisms for fully decentralized trustless operation. We demonstrate working implementations of Origami stores with three post-quantum signature libraries-qTESLA, Dilithium, and Picnic-to illustrate its scalability and practicality for real-world applications.