javascript将url中的参数加密解密代码

<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>