import javax.swing.*;
import java.security.SecureRandom;
import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;
import java.util.Random ;
import java.io.*;
class KeyStorage {
byte[] skey = new byte[1000];
String skeyString;
static byte[] raw;

public KeyStorage() {
generateSymmetricKey();
writeKey();
}
void generateSymmetricKey() {
try {
Random r = new Random();
int num = r.nextInt(10000);
String knum = String.valueOf(num);
byte[] knumb = knum.getBytes();
skey=getRawKey(knumb);
skeyString = new String(skey);
System.out.println("AES Symmetric key = "+skeyString);
}
catch(Exception e) {
System.out.println(e);
}
}
private static byte[] getRawKey(byte[] seed) throws Exception {
KeyGenerator kgen = KeyGenerator.getInstance("AES");
SecureRandom sr = SecureRandom.getInstance("SHA1PRNG");
sr.setSeed(seed);
kgen.init(128, sr); // 192 and 256 bits may not be available
SecretKey skey = kgen.generateKey();
raw = skey.getEncoded();
return raw;
}
void writeKey() {
try {
FileOutputStream f0;
f0 = new FileOutputStream("D://symmetricKey.txt");
f0.write(skey);
f0.close();
}
catch(Exception e) {
System.out.println(e);
}
}
public static void main(String args[]) {
KeyStorage ks = new KeyStorage();
}
}