Yoshiaki Shiraishi Youji Fukuta Masakatu Morii Remote Access VPN with Port Protection Function by Mobile Codes. 16-26 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=2908&spage=16 2003 conf/wisa/2003 WISA db/conf/wisa/wisa2003.html#ShiraishiFM03