采用密码加密的javascript字符串加密、解密程序

<SCRIPT LANGUAGE="JavaScript">
<!-- Begin

function Encrypt(str, pwd) {
if(str=="")return "";
str = escape(str);
if(!pwd || pwd==""){ var pwd="1234"; }
pwd = escape(pwd);
if(pwd == null || pwd.length <= 0) {
alert("Please enter a password with which to encrypt the message.");
return null;
}
var prand = "";
for(var I=0; I<pwd.length; I++) {
prand += pwd.charCodeAt(I).toString();
}
var sPos = Math.floor(prand.length / 5);
var mult = parseInt(prand.charAt(sPos) + prand.charAt(sPos*2) + prand.charAt(sPos*3) + prand.charAt(sPos*4) + prand.charAt(sPos*5));

var incr = Math.ceil(pwd.length / 2);
var modu = Math.pow(2, 31) - 1;
if(mult < 2) {
alert("Algorithm cannot find a suitable hash. Please choose a different password. /nPossible considerations are to choose a more complex or longer password.");
return null;
}
var salt = Math.round(Math.random() * 1000000000) % 100000000;
prand += salt;
while(prand.length > 10) {
prand = (parseInt(prand.substring(0, 10)) + parseInt(prand.substring(10, prand.length))).toString();
}
prand = (mult * prand + incr) % modu;
var enc_chr = "";
var enc_str = "";
for(var I=0; I<str.length; I++) {
enc_chr = parseInt(str.charCodeAt(I) ^ Math.floor((prand / modu) * 255));
if(enc_chr < 16) {
enc_str += "0" + enc_chr.toString(16);
}else
enc_str += enc_chr.toString(16);
prand = (mult * prand + incr) % modu;
}
salt = salt.toString(16);
while(salt.length < 8)salt = "0" + salt;
enc_str += salt;
return enc_str;
}

function Decrypt(str, pwd) {
if(str=="")return "";
if(!pwd || pwd==""){ var pwd="1234"; }
pwd = escape(pwd);
if(str == null || str.length < 8) {
alert("A salt value could not be extracted from the encrypted message because it's length is too short. The message cannot be decrypted.");
return;
}
if(pwd == null || pwd.length <= 0) {
alert("Please enter a password with which to decrypt the message.");
return;
}
var prand = "";
for(var I=0; I<pwd.length; I++) {
prand += pwd.charCodeAt(I).toString();
}
var sPos = Math.floor(prand.length / 5);
var mult = parseInt(prand.charAt(sPos) + prand.charAt(sPos*2) + prand.charAt(sPos*3) + prand.charAt(sPos*4) + prand.charAt(sPos*5));
var incr = Math.round(pwd.length / 2);
var modu = Math.pow(2, 31) - 1;
var salt = parseInt(str.substring(str.length - 8, str.length), 16);
str = str.substring(0, str.length - 8);
prand += salt;
while(prand.length > 10) {
prand = (parseInt(prand.substring(0, 10)) + parseInt(prand.substring(10, prand.length))).toString();
}
prand = (mult * prand + incr) % modu;
var enc_chr = "";
var enc_str = "";
for(var I=0; I<str.length; I+=2) {
enc_chr = parseInt(parseInt(str.substring(I, I+2), 16) ^ Math.floor((prand / modu) * 255));
enc_str += String.fromCharCode(enc_chr);
prand = (mult * prand + incr) % modu;
}
return unescape(enc_str);
}
// End -->
</script>