POTSHARDS: Secure Long-Term Archival Storage Without Encryption

Published as Storage Systems Research Center Technical Report UCSC-SSRC-06-03. Later version published in USENIX 2007.

Abstract

Modern archival storage systems either store data in the clear, ignoring security, or rely on keyed encryption to ensure privacy. However, the use of encryption is a major concern when data must be stored an indefinite period of time—key management becomes increasingly difficult as file lifetimes increase, and data loss becomes increasingly likely because keys are a single point of failure and losing a key is comparable to data deletion. Moreover, traditional systems are subject to the obsolescence of encryption algorithms themselves, which can expose petabytes of data the instant a cryptographic algorithm is broken.

To address these concerns, we developed POTSHARDS, an archival storage system that addresses the long-term security needs of data with very long lifetimes without the use of encryption. POTSHARDS separates security and redundancy by utilizing two levels of secret splitting in a way that allows the original data to be reconstructed from the stored pieces. However, the data structures used in POTSHARDS are also designed in such a way that an unauthorized user attempting to collect sufficient shares to reconstruct any data will not go unnoticed because it is very difficult to launch a targeted attack on the system, even with unrestricted access to a few archives. Since POTSHARDS provides secure storage for arbitrarily long periods of time, its data structures include built-in support for consistency checking and data migration. An evaluation of our POTSHARDS implementation shows that it stores and retrieves data at 2.5–5 MB/s, demonstrates its ability to recover user data given all of the pieces a user has stored across the archives, and shows its ability to recover from the loss of an entire archive.

Publication date:
September 2006

Authors:
Mark W. Storer
Kevin Greenan
Ethan L. Miller
Kaladhar Voruganti

Projects:
Archival Storage
Secure File and Storage Systems
Reliable Storage

Available media

Full paper text: PDF

Bibtex entry

@techreport{storer-ssrctr06,
  author       = {Mark W. Storer and Kevin Greenan and Ethan L. Miller and Kaladhar Voruganti},
  title        = {{POTSHARDS}: Secure Long-Term Archival Storage Without Encryption},
  institution  = {University of California, Santa Cruz},
  number       = {UCSC-SSRC-06-03},
  month        = sep,
  year         = {2006},
}