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

Abstract

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 The accumulation of outdated but undeletable data makes traditional blockchains non-scalable for practical applications.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.