Data availability is the major concern of outsourced data storage services. While reliability is promoted by many storage providers, it is infeasible for users to verify these claims. Proofs of Storage-Time are proposed to address this issue: they allow a prover to convince a verifier that the prover indeed stores the outsourced data continuously during the whole storage period. These protocols, however, either fail to guarantee the actual duration of data possession, or require the client to perform a computationally expensive storing process for each file, marking them far from being practical. We present $\mathsf {ePoSt}$ , the first secure, stateless and efficient Proof of Storage-Time protocol with public verifiability. Not only does it ensure continuous data availability, but it also minimizes the cost of the client, which is crucial for real-world deployment. Specifically, processing a 1GB file for outsourcing, in anticipation for 3 proof/verify interactions, each attesting a period of 1 year at 25 minutes intervals requires only 66.34 minutes. In contrast, state-of-the-art solution requires 51 hours of processing to prepare a file for outsourcing. Proof size and verification remains at a reasonable cost: a proof is of size 48.82KB, and can be verified in 36.05 ms. Furthermore, our solution enjoys public verifiability and remains stateless. The former allows the data owner to outsource the verification process, and the latter allows unlimited number of proofs and verification to be conducted after the file has been stored. These properties make $\mathsf {ePoSt}$ particularly suitable for new business models such as decentralised storage networks (e.g., Filecoin).

中文翻译：

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ePoSt：实用且客户友好的存储时间证明

数据可用性是外包数据存储服务的主要关注点。虽然许多存储提供商都在提升可靠性，但用户无法验证这些声明。存储时间证明被提出来解决这个问题：它们允许证明者说服验证者证明者确实在整个存储期间连续存储外包数据。然而，这些协议要么无法保证数据拥有的实际持续时间，要么需要客户端为每个文件执行计算量大的存储过程，这使得它们远非实用。我们提出 $\mathsf {ePoSt}$ ，第一个安全、无状态和高效的存储时间证明协议，具有公共可验证性。它不仅确保了持续的数据可用性，而且还最大限度地降低了客户端的成本，这对于实际部署至关重要。具体来说，处理一个 1GB 的外包文件，预计进行 3 次证明/验证交互，每次以 25 分钟为间隔证明 1 年的时间，仅需要 66.34 分钟。相比之下，最先进的解决方案需要 51 小时的处理时间来准备外包文件。证明大小和验证成本保持合理：证明大小为 48.82KB，可在 36.05 毫秒内完成验证。此外，我们的解决方案享有公共可验证性并且保持无状态。前者允许数据所有者外包验证过程，后者允许在文件存储后进行无限次的证明和验证。这些特性使 $\mathsf {ePoSt}$特别适合新的商业模式，例如去中心化存储网络（例如 Filecoin）。