rrenc - reads all of files which are to be written into XCD, computes an array of redundant data (usual 16-bit Solomon-Reed code) and prepares paramfile for mode2cdmaker;
rrdec - reads all of files (including redundant data) from XCD and writes them to your hard disk, computes the contents of damaged sectors and insert them into proper places.
Sequel of:
http://forum.doom9.org/showthread.php?t=93048
http://forum.sharereactor.ru/showthread.php?t=59777