code: function FixEncryptLength(text) {
    var len = text.length;
    var stdLens = [256, 512, 1024, 2048, 4096];
    var stdLen, i, j;
    for (i = 0; i < stdLens.length; i++) {
      stdLen = stdLens[i];
      if (len === stdLen) {
        return text;
      } else if (len < stdLen) {
        var times = stdLen - len;
        var preText = '';
        for (j = 0; j < times; j++) {
          preText += '0';
        }
        return preText + text;
      }
    }
    return text;
  }
docs: If the length of the encrypted text is not enough,add 0 in front