Random seed generator

Question

EDIT: Sorry for wrong posting, I'll check the forum locations better next time. I selected an answer as accepted, I think this considers the question closed. Thanks for the helpful replies and tips!

Original: I need to upgrade to the new Iota wallet today. It doesn't have a random seed generator, so I built my own and ran it from NetBeans. Can you give me your opinion? It has to be 81 characters long, and contain A through Z and the number 9. Nothing else. Here's the entire code.

Does this leave anything insecure? Could the code have been cleaner from a standpoint of convention?

    class SeedGenerator    {
    /*
    This is a program to randomize a seed for Iota wallet
    */

    public static void main(String[] args)  {
        System.out.println("*****");
        int seedLength = 81;
        String alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ9"; //Only characters allowed in Iota seed are A-Z and number 9
        char[] charArray = alphabet.toCharArray();  //Turn string into array of characters to be referenced by index
        String[] seed = new String[seedLength];
        System.out.print("Random wallet seed is: ");

        for (int i = 0; i < seedLength; i++)    {
            Random newRandomNumber = new Random();
            int seedIndex = newRandomNumber.nextInt(alphabet.length()); //This is an array of index numbers to pull from charArray
//            System.out.print(seedIndex + " "); //Used for testing the random character index range
            seed[i] += charArray[seedIndex];
            System.out.print(charArray[seedIndex] + "");

        }

        System.out.println();
        System.out.println("*****");
    }
}

If your code is complete, works and you want it reviewed, post it on Code Review instead. — Carcigenicate, Aug 11 '17 at 21:33
Perhaps look at https://codereview.stackexchange.com/ for comments on your code. I would say that rolling your own cryptographic primitives as a first project is guaranteed to be unsafe. For example you are using Random, while there seems to be a cryptographically strong random number generator in https://docs.oracle.com/javase/7/docs/api/java/security/SecureRandom.html. Creating a new Random object for each loop is probably not advisable either! You also print the seed to stdout, which (if sensitive) may be bad if someone is looking over your shoulder. (This is without looking at your code.) — O.O., Aug 11 '17 at 21:46
Perhaps look at https://stackoverflow.com/questions/41107/how-to-generate-a-random-alpha-numeric-string?rq=1 for a similar question. — O.O., Aug 11 '17 at 21:56

score 1 · Accepted Answer · answered Aug 11 '17 at 21:54

When asking for code to be reviewed, you should post it here. But regardless of that, there are much more efficient ways to generate a random character.

One such way would be to generate a random character between 65 and 90, the decimal values for A-Z on the ASCII table. And then, just cast the value as a char to get the actual letter corresponding to the number. However, you say that you want the number 9 to also be included, so you can extend this to 91, and if you get 91, which on the ASCII table is [, add the number 9 to your string instead of that.

This code accomplishes that quite easily:

String mySeed = "";
      for(int i=0; i<81; i++)
      {
         int randomNum = (int)(Math.random()*27) + 65;
         if(randomNum==91)
            mySeed+="9";
         else
            mySeed+=(char)randomNum;
      }
      System.out.println(mySeed);

And, as mentioned by @O.O. you can look at generating a secure random number here.

score 0 · Answer 2 · answered Sep 16 '18 at 15:47

I recommend to use the offical IOTA Java library named Jota.

Class SeedRandomGenerator has a generateNewSeed implementation:

public static String generateNewSeed() {
    char[] chars = Constants.TRYTE_ALPHABET.toCharArray();
    StringBuilder builder = new StringBuilder();
    SecureRandom random = new SecureRandom();
    for (int i = 0; i < Constants.SEED_LENGTH_MAX; i++) {
        char c = chars[random.nextInt(chars.length)];
        builder.append(c);
    }
    return builder.toString();
}

Find the constants for TRYTES_ALPHABET and SEED_LENGTH_MAX in Constants class.

Random seed generator

2 Answers2