The following code perfectly implements AES-128 encryption/decryption.
public static void main(String[] args) throws Exception
{
String input = JOptionPane.showInputDialog(null, "Enter your String");
System.out.println("Plaintext: " + input + "\n");
// Generate a key
KeyGenerator keygen = KeyGenerator.getInstance("AES");
keygen.init(128);
byte[] key = keygen.generateKey().getEncoded();
SecretKeySpec skeySpec = new SecretKeySpec(key, "AES");
// Generate IV randomly
SecureRandom random = new SecureRandom();
byte[] iv = new byte[16];
random.nextBytes(iv);
IvParameterSpec ivspec = new IvParameterSpec(iv);
// Initialize Encryption Mode
Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
cipher.init(Cipher.ENCRYPT_MODE, skeySpec, ivspec);
// Encrypt the message
byte[] encryption = cipher.doFinal(input.getBytes());
System.out.println("Ciphertext: " + encryption + "\n"); //
// Initialize the cipher for decryption
cipher.init(Cipher.DECRYPT_MODE, skeySpec, ivspec);
// Decrypt the message
byte[] decryption = cipher.doFinal(encryption);
System.out.println("Plaintext: " + new String(decryption) + "\n");
}
When I want to use AES-256, I thought that can be done by just modifying keygen.init(256); and byte[] iv = new byte[32];, however this becomes error (Exception in thread "main" java.security.InvalidKeyException: Illegal key size)! Can someone explain why error occurs when I made these two modification and what should I do. Thank you guys :)
