rot13 = { 
convert: function(a) {
             return a.replace(/[a-zA-Z]/g, function(c){return String.fromCharCode
                     ((c<="Z"?90:122)>=(c=c.charCodeAt(0)+13)?c:c-26);});
         },

write: function(a) {
           document.write(rot13.convert(a));
       },

mailto: function(a) {
            var match=/(.*)(@.*)/.exec(a);
            var s=rot13.convert(match[1])+match[2];
            document.write('<a href="mailto:'+s+'">'+s+'</a>');
        }

}