Thread: How to set secret key

Hi all,

Below is a des encryption/decryption algorithm i grab from online.

Questions:
1) How can i set my own secret key instead of auto set key

SecretKey key = KeyGenerator.getInstance("DES").generateKey();

2)How to i print the sboxes because my assignment require me to analysis sboxes ?

import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
 
class DesEncrypter {
  Cipher ecipher;
 
  Cipher dcipher;
 
  DesEncrypter(SecretKey key) throws Exception {
    ecipher = Cipher.getInstance("DES");
    dcipher = Cipher.getInstance("DES");
    ecipher.init(Cipher.ENCRYPT_MODE, key);
    dcipher.init(Cipher.DECRYPT_MODE, key);
  }
 
  public String encrypt(String str) throws Exception {
    // Encode the string into bytes using utf-8
    byte[] utf8 = str.getBytes("UTF8");
 
    // Encrypt
    byte[] enc = ecipher.doFinal(utf8);
 
    // Encode bytes to base64 to get a string
    return new sun.misc.BASE64Encoder().encode(enc);
  }
 
  public String decrypt(String str) throws Exception {
    // Decode base64 to get bytes
    byte[] dec = new sun.misc.BASE64Decoder().decodeBuffer(str);
 
    byte[] utf8 = dcipher.doFinal(dec);
 
    // Decode using utf-8
    return new String(utf8, "UTF8");
  }
}
 
public class Main {
  public static void main(String[] argv) throws Exception {
    SecretKey key = KeyGenerator.getInstance("DES").generateKey();
    DesEncrypter encrypter = new DesEncrypter(key);
    String encrypted = encrypter.encrypt("Don't tell anybody!");
    String decrypted = encrypter.decrypt(encrypted);
  }
}

Originally Posted by JavaPF

Hopefully this link will help you - Secret Key Cryptography Tutorial

Thanks !! The link was useful. I found the answer i looking for @ the comment section.

Regarding my second question about the sbox. It is possible to have access to the sboxes?