code: public static String generateRandomKey(int pLength) {
      int asciiFirst = 48;
      int asciiLast = 122;
      Integer[] exceptions = { 58,59,60,61,62,63,91,92,93,94,96 };
  
      List<Integer> exceptionsList = Arrays.asList(exceptions);
      SecureRandom random = new SecureRandom();
      StringBuilder builder = new StringBuilder();
      for (int i=0; i<pLength; i++) {
          int charIndex;
          do {
              charIndex = random.nextInt(asciiLast - asciiFirst + 1) + asciiFirst;
          }
          while (exceptionsList.contains(charIndex));
  
          builder.append((char) charIndex);
      }
  
      return builder.toString();
  }
docs: generate a Random key
  @param pLength
  @return the reandom key with the given length