Slashdot Mirror
A Move to Secure Data by Scattering the Pieces
uler writes "The NY Times has an article about an interesting new open source storage project. Unlike data storage mechanisms today that work 'by making multiple copies of data,' the Cleversafe software takes an 'approach based on dispersing data in encrypted slices.' It's an elegant solution and one that's been a long time coming: the software uses algorithmic techniques known by mathematicians since the 70's. Adi Shamir (of RSA) first wrote of information dispersal is his 1979 paper 'How to Share a Secret (pdf).'"
Freenet uses forward error correction, which guarantees that the original data can be reconstructed given a sufficient number of pieces. Shamir's information dispersal algorithm makes the additional guarantee that nothing can be learned about the original data unless you have enough pieces to reconstruct it.
(Fyi: this link to the New York Times article bypasses any need to login/register with the nytimes.com website.)
I'm the Cleversafe Dispersed Storage software-development project leader. I work with Chris Gladwin (mentioned in the New York Times article) as a fellow manager at Cleversafe.
I offer some comments below to help outline some of the unique aspects of the Cleversafe technology.
Encryption is not dispersal. Cleversafe provides both, and then some. The Cleversafe Dispersed Storage software disperses any "datasource" (typically a file) into several slices (our current software current uses 11 slices in an 11-lose-any-5 scheme; future versions may use additional schemes with "wider" slice sets). Additionally, our software also encrypts, compresses, scrambles, and signs the datasource content, but we are not trying to reinvent the wheel: other software technologies exist to do these things, and we leverage them extensively.
We found that a bigger challenge than creating or managing dispersal algorithms was to make the entire storage system regardless of the dispersal algorithm used (and we design the system to be dispersal-scheme agnostic). The meta-data management system and many other things took us far longer to implement then the Cleversafe IDA. It's not hard to use Reed-Solomon, or some other algorithm on a single file or a small set of files and disperse the slices by hand onto several different system (or use variants of this like the 3-piece secret story with Amy, Bob, and Charlie mentioned above). It's much harder to manage this across an entire file system (with hundreds of thousand of files--or many more depending on the file system) for an unlimited number of file systems from all the various users across to be stored on heterogeneous set of an unlimited-number of geographically-dispersed, commodity-storage nodes in a completely-decentralized way with no dependence on the original source of the data (eg, you could sledgehammer your laptop and not lose any data that's stored on our grid/storage service). (I apologize for that run-on sentence.)
Further, dispersed-storage systems do not require replication. (Dispersal systems may replicate data for performance purposes, if at all, depending on the application/configuration/installation/context.) If a system replicates entire copies of the data (be they encrypted or not) then it, by (our) definition is not a dispersed-storage system. So a continual question I have when evaluate other systems: do they replicate the data in whole or not? Most systems replicate.
Cleversafe is not the first to present a dispersal system, but we like to think we are the first to make it broadly usable by people and inter-operable with other systems. See our cmdline client (which will soon have continous-backup and XML-programmable policy management), our Dispersed Storage API, our dsgfs file system, a soon-to-be released GUI client, and future "connectors" (what we call the applications that leverage our technology) to come, all available at http://www.cleversafe.org.
A side note: "revision management" is built into the Cleversafe system to address what I call "soft" failures (accidental deletes, application failures, etc) vs. "hard" failures (hard disk crashes) as well as archival requirements.
I believe that the concept of "dispersed storage" will eventually change how the world thinks about storage systems--regardless of whether or not these are Cleversafe-based systems (I think Cleversafe presents the best such system, but I of course am biased).