Many archival storage systems rely on keyed encryption to ensure privacy. A data object in such a system is exposed once the key used to encrypt the data is compromised. When storing data for as long as a few decades or centuries, the use of keyed encryption becomes a real concern. The exposure of a key is bounded by computation effort and management of encryption keys becomes as much of a problem as the management of the data the key is protecting. POTSHARDS is a secure, distributed, very long-term archival storage system that eliminates the use of keyed encryption through the use of unconditionally secure secret sharing. A (m,n) unconditionally secure secret sharing scheme splits an object up into n shares, which provably gives no information about the object, unless m of the shares collaborate.

POTSHARDS separates security and redundancy by utilizing two levels of secret sharing. This allows for secure reconstruction upon failure and more flexible storage patterns. The data structures used in POTSHARDS are organized in such a way that an unauthorized user attempting to collect shares will not go unnoticed since it is very difficult to launch a targeted attack on the system. A malicious user would have a difficult time finding the shares for a particular file in a timely or efficient manner. Since POTSHARDS provides secure storage for arbitrarily long periods of time, its data structures include built-in support for consistency checking and data migration. This enables reliable data churning and the movement of data between storage devices.