pkgsrc/misc/parchive/DESCR

"Parchive" implements a RAID-like system for multi-part archives. Such
archives are commonly posted to Usenet binary newsgroups. Typically, a
poster will construct 2 to 5 parity files for a multi-part archive
consisting of somewhere in the neighborhood of 15 to 50 equal sized parts.
These parity files contain a Reed-Solomon encoding of the original files.
He'll then post all of them along with the original parts, so if any number
of those original parts are lost or corrupted in transit (up to the number
of parity files), a receiver may reconstruct them from only that number
of parity files.

Though quickly growing in popularity for its intended application, the
format of the parity files is sufficiently general to be useful for other
applicatons as well. The format itself is in the public domain.