加密实现
  

  //str 是想加密的字符串
  

  //pwd 是key
  

  function encrypt(str, 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. Possible 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;
  

  }
  

  解密实现
  

  

  function decrypt(str, 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 enc_str;
  

  }