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[Colloquium] POTSHARDS: Secure Long-Term Archival Storage Without Encryption

April 19, 2007

Watch Colloquium:

AVI file (358 MB)
Quicktime (130 MB)


  • Date: Thursday, April 19th, 2007 
  • Time: 11 am— 12:15 pm 
  • Place: ECE 118

Ethan L. Miller 
University of California at Santa Cruz

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. 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.