一段有用的javascript加密解密

今天在做一个老项目时，遇到一个需求，在javascript将url中的参数加密解密，从网上找发现了这段有用的代码：

<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>

以后碰到加密解密问题，直接将上述代码写成一个js文件，就搞定。省事了。。。。