Unrarhp is a Unix command line brute forcer to recover the passwords of
RAR archives encrypted with the RAR 3.x "-hp" option.  This option,
contrary to "-p", also encrypts the block headers and protects metadata
such as filenames, etc.  As of June 2010, unrarhp is the only RAR "-hp"
brute forcer that is open source and free.

http://www.zorinaq.com/projs.html
http://www.zorinaq.com/unrarhp/