Paper 2020/840

Proof of Storage-Time: Efficiently Checking Continuous Data Availability

Giuseppe Ateniese, Long Chen, Mohammad Etemad, and Qiang Tang


A high-quality outsourced storage service is crucial for many existing applications. For example, hospitals and data centers need to guarantee the availability of their systems to perform routine daily activities. Such a system should protect users against downtime and ensure data availability over time. Continuous data availability is a critical property to measure the quality of an outsourced storage service, which implies that outsourced data is continuously available to the server during the entire storage period. We formally study the Proof of Storage-Time (PoSt), the notion initially proposed in the Filecoin whitepaper, which enables a verifier to audit the continuous data availability of an outsourced storage service. We provide a formal security model of PoSt and generic constructions that are proven secure under our definition. Moreover, our concrete instantiation can yield a PoSt protocol with an extremely efficient verification: a single hash computation to verify a proof of size around 200 bits. This makes our scheme applicable even in the decentralized storage marketplace enabled by blockchain.

Available format(s)
Publication info
Published elsewhere. Minor revision. NDSS 2020
Outsourced storageContinuous availabilityProof of storage
Contact author(s)
longchen @ njit edu
qiang @ njit edu
gatenies @ stevens edu
2020-07-12: received
Short URL
Creative Commons Attribution


      author = {Giuseppe Ateniese and Long Chen and Mohammad Etemad and Qiang Tang},
      title = {Proof of Storage-Time: Efficiently Checking Continuous Data Availability},
      howpublished = {Cryptology ePrint Archive, Paper 2020/840},
      year = {2020},
      doi = {10.14722/ndss.2020.24427},
      note = {\url{}},
      url = {}
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