POTSHARDS: Secure Long-Term Storage Without Encryption

Appeared in Proceedings of the 2007 USENIX Technical Conference.

Abstract

Users are storing ever-increasing amounts of information digitally, driven by many factors including government regulations and the public's desire to digitally record their personal histories. Unfortunately, many of the security mechanisms that modern systems rely upon, such as encryption, are poorly suited for storing data for indefinitely long periods of time—it is very difficult to manage keys and update cryptosystems to provide secrecy through encryption over periods of decades. Worse, an adversary who can compromise an archive need only wait for cryptanalysis techniques to catch up to the encryption algorithm used at the time of the compromise in order to obtain "secure" data. To address these concerns, we have developed POTSHARDS, an archival storage system that provides long-term security for data with very long lifetimes without using encryption. Secrecy is achieved by using provably secure secret splitting and spreading the resulting shares across separately-managed archives. Providing availability and data recovery in such a system can be difficult; thus, we use a new technique, approximate pointers, in conjunction with secure distributed RAID techniques to provide availability and reliability across independent archives. To validate our design, we developed a prototype POTSHARDS implementation, which has demonstrated "normal" storage and retrieval of user data using indexes, the recovery of user data using only the pieces a user has stored across the archives and the reconstruction of an entire failed archive.

Publication date:
June 2007

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

Projects:
Archival Storage
Secure File and Storage Systems

Available media

Full paper text: PDF
Presentation: slides

Bibtex entry

@inproceedings{storer-usenix07,
  author       = {Mark W. Storer and Kevin Greenan and Ethan L. Miller and Kaladhar Voruganti},
  title        = {{POTSHARDS}: Secure Long-Term Storage Without Encryption},
  booktitle    = {Proceedings of the 2007 USENIX Technical Conference},
  pages        = {143-156},
  month        = jun,
  year         = {2007},
}