为了系统的安全，前端一般需要对密码进行md5加密，然后传输给后台处理。
需要引入md5.js，代码如下：
1 var hexcase = 0;
2 var b64pad = "";
3 var chrsz = 8;
4 function hex_md5(s){ return binl2hex(core_md5(str2binl(s), s.length * chrsz));}
5 function b64_md5(s){ return binl2b64(core_md5(str2binl(s), s.length * chrsz));}
6 function hex_hmac_md5(key, data) { return binl2hex(core_hmac_md5(key, data)); }
7 function b64_hmac_md5(key, data) { return binl2b64(core_hmac_md5(key, data)); }
8 function calcMD5(s){ return binl2hex(core_md5(str2binl(s), s.length * chrsz));}
9
10 function md5_vm_test()
11 {
12 return hex_md5("abc") == "900150983cd24fb0d6963f7d28e17f72";
13 }
14
15 function core_md5(x, len)
16 {
17
18 x[len >> 5] |= 0x80 << ((len) % 32);
19 x[(((len + 64) >>> 9) << 4) + 14] = len;
20 var a = 1732584193;
21 var b = -271733879;
22 var c = -1732584194;
23 var d = 271733878;
24 for(var i = 0; i < x.length; i += 16)
25 {
26 var olda = a;
27 var oldb = b;
28 var oldc = c;
29 var oldd = d;
30
31 a = md5_ff(a, b, c, d, x[i+ 0], 7 , -680876936);
32 d = md5_ff(d, a, b, c, x[i+ 1], 12, -389564586);
33 c = md5_ff(c, d, a, b, x[i+ 2], 17, 606105819);
34 b = md5_ff(b, c, d, a, x[i+ 3], 22, -1044525330);
35 a = md5_ff(a, b, c, d, x[i+ 4], 7 , -176418897);
36 d = md5_ff(d, a, b, c, x[i+ 5], 12, 1200080426);
37 c = md5_ff(c, d, a, b, x[i+ 6], 17, -1473231341);
38 b = md5_ff(b, c, d, a, x[i+ 7], 22, -45705983);
39 a = md5_ff(a, b, c, d, x[i+ 8], 7 , 1770035416);
40 d = md5_ff(d, a, b, c, x[i+ 9], 12, -1958414417);
41 c = md5_ff(c, d, a, b, x[i+10], 17, -42063);
42 b = md5_ff(b, c, d, a, x[i+11], 22, -1990404162);
43 a = md5_ff(a, b, c, d, x[i+12], 7 , 1804603682);
44 d = md5_ff(d, a, b, c, x[i+13], 12, -40341101);
45 c = md5_ff(c, d, a, b, x[i+14], 17, -1502002290);
46 b = md5_ff(b, c, d, a, x[i+15], 22, 1236535329);
47 a = md5_gg(a, b, c, d, x[i+ 1], 5 , -165796510);
48 d = md5_gg(d, a, b, c, x[i+ 6], 9 , -1069501632);
49 c = md5_gg(c, d, a, b, x[i+11], 14, 643717713);
50 b = md5_gg(b, c, d, a, x[i+ 0], 20, -373897302);
51 a = md5_gg(a, b, c, d, x[i+ 5], 5 , -701558691);
52 d = md5_gg(d, a, b, c, x[i+10], 9 , 38016083);
53 c = md5_gg(c, d, a, b, x[i+15], 14, -660478335);
54 b = md5_gg(b, c, d, a, x[i+ 4], 20, -405537848);
55 a = md5_gg(a, b, c, d, x[i+ 9], 5 , 568446438);
56 d = md5_gg(d, a, b, c, x[i+14], 9 , -1019803690);
57 c = md5_gg(c, d, a, b, x[i+ 3], 14, -187363961);
58 b = md5_gg(b, c, d, a, x[i+ 8], 20, 1163531501);
59 a = md5_gg(a, b, c, d, x[i+13], 5 , -1444681467);
60 d = md5_gg(d, a, b, c, x[i+ 2], 9 , -51403784);
61 c = md5_gg(c, d, a, b, x[i+ 7], 14, 1735328473);
62 b = md5_gg(b, c, d, a, x[i+12], 20, -1926607734);
63 a = md5_hh(a, b, c, d, x[i+ 5], 4 , -378558);
64 d = md5_hh(d, a, b, c, x[i+ 8], 11, -2022574463);
65 c = md5_hh(c, d, a, b, x[i+11], 16, 1839030562);
66 b = md5_hh(b, c, d, a, x[i+14], 23, -35309556);
67 a = md5_hh(a, b, c, d, x[i+ 1], 4 , -1530992060);
68 d = md5_hh(d, a, b, c, x[i+ 4], 11, 1272893353);
69 c = md5_hh(c, d, a, b, x[i+ 7], 16, -155497632);
70 b = md5_hh(b, c, d, a, x[i+10], 23, -1094730640);
71 a = md5_hh(a, b, c, d, x[i+13], 4 , 681279174);
72 d = md5_hh(d, a, b, c, x[i+ 0], 11, -358537222);
73 c = md5_hh(c, d, a, b, x[i+ 3], 16, -722521979);
74 b = md5_hh(b, c, d, a, x[i+ 6], 23, 76029189);
75 a = md5_hh(a, b, c, d, x[i+ 9], 4 , -640364487);
76 d = md5_hh(d, a, b, c, x[i+12], 11, -421815835);
77 c = md5_hh(c, d, a, b, x[i+15], 16, 530742520);
78 b = md5_hh(b, c, d, a, x[i+ 2], 23, -995338651);
79 a = md5_ii(a, b, c, d, x[i+ 0], 6 , -198630844);
80 d = md5_ii(d, a, b, c, x[i+ 7], 10, 1126891415);
81 c = md5_ii(c, d, a, b, x[i+14], 15, -1416354905);
82 b = md5_ii(b, c, d, a, x[i+ 5], 21, -57434055);
83 a = md5_ii(a, b, c, d, x[i+12], 6 , 1700485571);
84 d = md5_ii(d, a, b, c, x[i+ 3], 10, -1894986606);
85 c = md5_ii(c, d, a, b, x[i+10], 15, -1051523);
86 b = md5_ii(b, c, d, a, x[i+ 1], 21, -2054922799);
87 a = md5_ii(a, b, c, d, x[i+ 8], 6 , 1873313359);
88 d = md5_ii(d, a, b, c, x[i+15], 10, -30611744);
89 c = md5_ii(c, d, a, b, x[i+ 6], 15, -1560198380);
90 b = md5_ii(b, c, d, a, x[i+13], 21, 1309151649);
91 a = md5_ii(a, b, c, d, x[i+ 4], 6 , -145523070);
92 d = md5_ii(d, a, b, c, x[i+11], 10, -1120210379);
93 c = md5_ii(c, d, a, b, x[i+ 2], 15, 718787259);
94 b = md5_ii(b, c, d, a, x[i+ 9], 21, -343485551);
95
96 a = safe_add(a, olda);
97 b = safe_add(b, oldb);
98 c = safe_add(c, oldc);
99 d = safe_add(d, oldd);
100 }
101 return Array(a, b, c, d);
102
103 }
104
105 function md5_cmn(q, a, b, x, s, t)
106 {
107 return safe_add(bit_rol(safe_add(safe_add(a, q), safe_add(x, t)), s),b);
108 }
109 function md5_ff(a, b, c, d, x, s, t)
110 {
111 return md5_cmn((b & c) | ((~b) & d), a, b, x, s, t);
112 }
113 function md5_gg(a, b, c, d, x, s, t)
114 {
115 return md5_cmn((b & d) | (c & (~d)), a, b, x, s, t);
116 }
117 function md5_hh(a, b, c, d, x, s, t)
118 {
119 return md5_cmn(b ^ c ^ d, a, b, x, s, t);
120 }
121 function md5_ii(a, b, c, d, x, s, t)
122 {
123 return md5_cmn(c ^ (b | (~d)), a, b, x, s, t);
124 }
125
126 function core_hmac_md5(key, data)
127 {
128 var bkey = str2binl(key);
129 if(bkey.length > 16) bkey = core_md5(bkey, key.length * chrsz);
130
131 var ipad = Array(16), opad = Array(16);
132 for(var i = 0; i < 16; i++)
133 {
134 ipad[i] = bkey[i] ^ 0x36363636;
135 opad[i] = bkey[i] ^ 0x5C5C5C5C;
136 }
137
138 var hash = core_md5(ipad.concat(str2binl(data)), 512 + data.length * chrsz);
139 return core_md5(opad.concat(hash), 512 + 128);
140 }
141
142 function safe_add(x, y)
143 {
144 var lsw = (x & 0xFFFF) + (y & 0xFFFF);
145 var msw = (x >> 16) + (y >> 16) + (lsw >> 16);
146 return (msw << 16) | (lsw & 0xFFFF);
147 }
148
149 function bit_rol(num, cnt)
150 {
151 return (num << cnt) | (num >>> (32 - cnt));
152 }
153
154 function str2binl(str)
155 {
156 var bin = Array();
157 var mask = (1 << chrsz) - 1;
158 for(var i = 0; i < str.length * chrsz; i += chrsz)
159 bin[i>>5] |= (str.charCodeAt(i / chrsz) & mask) << (i%32);
160 return bin;
161 }
162
163 function binl2hex(binarray)
164 {
165 var hex_tab = hexcase ? "0123456789ABCDEF" : "0123456789abcdef";
166 var str = "";
167 for(var i = 0; i < binarray.length * 4; i++)
168 {
169 str += hex_tab.charAt((binarray[i>>2] >> ((i%4)*8+4)) & 0xF) +
170 hex_tab.charAt((binarray[i>>2] >> ((i%4)*8 )) & 0xF);
171 }
172 return str;
173 }
174
175 function binl2b64(binarray)
176 {
177 var tab = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
178 var str = "";
179 for(var i = 0; i < binarray.length * 4; i += 3)
180 {
181 var triplet = (((binarray[i >> 2] >> 8 * ( i %4)) & 0xFF) << 16)
182 | (((binarray[i+1 >> 2] >> 8 * ((i+1)%4)) & 0xFF) << 8 )
183 | ((binarray[i+2 >> 2] >> 8 * ((i+2)%4)) & 0xFF);
184 for(var j = 0; j < 4; j++)
185 {
186 if(i * 8 + j * 6 > binarray.length * 32) str += b64pad;
187 else str += tab.charAt((triplet >> 6*(3-j)) & 0x3F);
188 }
189 }
190 return str;
191 }
用法：将密码作为hex_md5的参数传入，即可加密成功，如以下代码所示：
1 var data = {
2 originPassword:hex_md5($('.oldPwd').val()),
3 password:hex_md5($('.newPwd').val())
4 }
MD5的英文是Message Digest Algorithm（信息摘要算法），是不可逆的算法，只能通过暴力破解，所以较为安全。