javascript增加干扰数据实现简单加密效果

var lishustr = "qwertyuiopasdfghjklmnbvcxz"; 
var s = lishustr.split(""); 
var lishua = ""; var lishub = ""; var lishuc = ""; var lishud = ""; 
lishua = s[getRandomNum(1,26)]; lishub = s[getRandomNum(1,26)]; lishuc = s[getRandomNum(1,26)]; lishud = s[getRandomNum(1,26)]; 
switch ("abcdefghijklmnopqrstuvwxyz".indexOf(lishud) + 1) { 
case 1: case 2: case 3: case 4: case 5: case 6: case 7: 
md5words = md5words + lishua + lishub + lishuc + lishud; break; 
case 8: case 9: case 10: case 11: case 12: case 13: case 14: 
md5words = lishua + md5words + lishub + lishuc + lishud; break; 
case 15: case 16: case 17: case 18: case 19: case 20: 
md5words = lishua + lishub + md5words + lishuc + lishud; break; 
case 21: case 22: case 23: case 24: case 25: case 26: 
md5words = lishua + lishub + lishuc + md5words + lishud; break; 
} 
function getRandomNum(lbound, ubound) { 
return (Math.floor(Math.random() * (ubound - lbound)) + lbound); 
}