客户说我的***系统登录时密码是明文传输，不高兴，我对HTTPS不太了解，那我用MD5加密下，虽然不能保证万无一失，但也好过明文传输嘛。

说下大概的过程：打开登录的JSP页面时，生成一个随机字符串，放在session里面，以便后台也可以拿到。客户输入用户名和密码点击"登录"时，拿到密码和随机字符串，拼接在一起后利用js生成MD5字符串。然后用js把那个password的value改成MD5字符串，再提交表单。

后台拿到随机字符串和用户名和MD5字符串，通过用户名到数据库查询密码，用密码和随机字符串拼接在一起生成MD5字符串，用生成的MD5字符串和前台传过来的MD5字符串进行匹配，如果一致就通过验证。

------------------------------前台-------------------------------------

jsp页面生成随机数：

<%

String pageName = pageContext.getRequest().getParameter("pageName");
pageName = StringUtils.filterUnsafeChars(pageName);
//产生随机数，和密码一起生成MD5
request.getSession().setAttribute("md5RandomKey", StringUtils.getRandomNum(10));

%>

	function encryptionPassword(){	          
	     var hash = MD5($("user_password").value+"${md5RandomKey}");  
	     $("user_password").value = hash;  
	    } 

/*
 * A JavaScript implementation of the RSA Data Security, Inc. MD5 Message
 * Digest Algorithm, as defined in RFC 1321.
 * Copyright (C) Paul Johnston 1999 - 2000.
 * Updated by Greg Holt 2000 - 2001.
 * See http://pajhome.org.uk/site/legal.html for details.
 */
var hex_chr = "0123456789abcdef";
function rhex(num) {
	str = "";
	for (j = 0; j <= 3; j++) {
		str += hex_chr.charAt((num >> (j * 8 + 4)) & 15) + hex_chr.charAt((num >> (j * 8)) & 15);
	}
	return str;
}
function str2blks_MD5(str) {
	nblk = ((str.length + 8) >> 6) + 1;
	blks = new Array(nblk * 16);
	for (i = 0; i < nblk * 16; i++) {
		blks[i] = 0;
	}
	for (i = 0; i < str.length; i++) {
		blks[i >> 2] |= str.charCodeAt(i) << ((i % 4) * 8);
	}
	blks[i >> 2] |= 128 << ((i % 4) * 8);
	blks[nblk * 16 - 2] = str.length * 8;
	return blks;
}
function add(x, y) {
	var lsw = (x & 65535) + (y & 65535);
	var msw = (x >> 16) + (y >> 16) + (lsw >> 16);
	return (msw << 16) | (lsw & 65535);
}
function rol(num, cnt) {
	return (num << cnt) | (num >>> (32 - cnt));
}
function cmn(q, a, b, x, s, t) {
	return add(rol(add(add(a, q), add(x, t)), s), b);
}
function ff(a, b, c, d, x, s, t) {
	return cmn((b & c) | ((~b) & d), a, b, x, s, t);
}
function gg(a, b, c, d, x, s, t) {
	return cmn((b & d) | (c & (~d)), a, b, x, s, t);
}
function hh(a, b, c, d, x, s, t) {
	return cmn(b ^ c ^ d, a, b, x, s, t);
}
function ii(a, b, c, d, x, s, t) {
	return cmn(c ^ (b | (~d)), a, b, x, s, t);
}
function MD5(str) {
	x = str2blks_MD5(str);
	var a = 1732584193;
	var b = -271733879;
	var c = -1732584194;
	var d = 271733878;
	for (i = 0; i < x.length; i += 16) {
		var olda = a;
		var oldb = b;
		var oldc = c;
		var oldd = d;
		a = ff(a, b, c, d, x[i + 0], 7, -680876936);
		d = ff(d, a, b, c, x[i + 1], 12, -389564586);
		c = ff(c, d, a, b, x[i + 2], 17, 606105819);
		b = ff(b, c, d, a, x[i + 3], 22, -1044525330);
		a = ff(a, b, c, d, x[i + 4], 7, -176418897);
		d = ff(d, a, b, c, x[i + 5], 12, 1200080426);
		c = ff(c, d, a, b, x[i + 6], 17, -1473231341);
		b = ff(b, c, d, a, x[i + 7], 22, -45705983);
		a = ff(a, b, c, d, x[i + 8], 7, 1770035416);
		d = ff(d, a, b, c, x[i + 9], 12, -1958414417);
		c = ff(c, d, a, b, x[i + 10], 17, -42063);
		b = ff(b, c, d, a, x[i + 11], 22, -1990404162);
		a = ff(a, b, c, d, x[i + 12], 7, 1804603682);
		d = ff(d, a, b, c, x[i + 13], 12, -40341101);
		c = ff(c, d, a, b, x[i + 14], 17, -1502002290);
		b = ff(b, c, d, a, x[i + 15], 22, 1236535329);
		a = gg(a, b, c, d, x[i + 1], 5, -165796510);
		d = gg(d, a, b, c, x[i + 6], 9, -1069501632);
		c = gg(c, d, a, b, x[i + 11], 14, 643717713);
		b = gg(b, c, d, a, x[i + 0], 20, -373897302);
		a = gg(a, b, c, d, x[i + 5], 5, -701558691);
		d = gg(d, a, b, c, x[i + 10], 9, 38016083);
		c = gg(c, d, a, b, x[i + 15]