Let's say a file is posted in 22 parts. User Alice receives all but parts 5 and 7. User Bob receives all but parts 5,13, and 19.

Using PAR files (calculated from the original parts) the missing parts may be "filled in". The amount of PAR files needed to reconstruct missing parts is equal to the maximum number of parts someone is missing. In the above example, if 3 PAR files were posted Bob could reconstruct his missing parts, but so could Alice... from the *same* PAR files even tho they might not be missing the same parts.

The PARchive homepage can be found at: www.sourceforge.net/projects/parchive