http://www.amiga-stuff.com/crunchers-download.html

http://io.debian.net/~tar/debian/xpk/

http://aminet.net/util/pack

developer xad, xfd, xpk master librarys http://www.dstoecker.eu/

cruncher ids http://www.amiga-stuff.com/crunchers-id.html

eg xfd includes a file id scanner

The ARJ link is dead. The content can still be found via the wayback machine at: http://web.archive.org/web/20090603093412/http://datacompression.info/ArchiveFormats/arj.txt

However, this spec only really covers the header format, not any of the compression algorithms nor encryption or garbling. (or the authenticity record information, for that matter.)