SaltedSBox.java

import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import java.util.Random;
import java.util.stream.Collectors;
import java.util.stream.IntStream;

public class SaltedSBox {
    private final Random rand;

    /**
     * Creates a generator to get randomly generated SBoxes.
     * The salt can be used to generate same sequence of SBoxes on different executions.
     * @param salt the seed for the random generation.
     */
    public SaltedSBox(long salt)
    {
        rand = new Random(salt);
    }

    /**
     * Call to get the next SBox.
     * @return the next generated SBox as a Byte[4][16].
     */
    public Byte[][] getNextSBox() {
        Byte[][] sbox = new Byte[4][16];
        for (int j = 0; j < 4; j++) {
            List<Byte> row =
                    IntStream.rangeClosed(0, 15)
                            .boxed()
                            .map(Integer::byteValue)
                            .collect(Collectors.toList());
            Collections.shuffle(row, rand);
            row.toArray(sbox[j]);
        }
        return sbox;
    }

    // example usage
    public static void main(String[] args) {
        SaltedSBox s = new SaltedSBox(1234567890);
        int countToGenerate = 3;
        for (int i = 0; i < countToGenerate; i++) {
            System.out.println("SBox "+(i+1)+": "+Arrays.deepToString(s.getNextSBox()));
        }
    }
}