AES Cipher not picking up IV
- by timothyjc
I am trying to use an IV with AES so that the encrypted text is unpredictable. However, the encrypted hex string is always the same.
I have actually tried a few methods of attempting to add some randomness by passing some additional parameters to the cipher init call:
1) Manual IV generation
byte[] iv = generateIv();
IvParameterSpec ivspec = new IvParameterSpec(iv);
2) Asking cipher to generate IV
AlgorithmParameters params = cipher.getParameters();
params.getParameterSpec(IvParameterSpec.class);
3) Using a PBEParameterSpec
byte[] encryptionSalt = generateSalt();
PBEParameterSpec pbeParamSpec = new PBEParameterSpec(encryptionSalt, 1000);
All of these seem to have no influence on the encrypted text.... help!!!
My code:
package com.citc.testencryption;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import javax.crypto.Cipher;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.PBEKeySpec;
import android.app.Activity;
import android.os.Bundle;
import android.util.Log;
public class Main extends Activity {
public static final int SALT_LENGTH = 20;
public static final int PBE_ITERATION_COUNT = 1000;
private static final String RANDOM_ALGORITHM = "SHA1PRNG";
private static final String PBE_ALGORITHM = "PBEWithSHA256And256BitAES-CBC-BC";
private static final String CIPHER_ALGORITHM = "PBEWithSHA256And256BitAES-CBC-BC";
private static final String TAG = Main.class.getSimpleName();
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
try {
String password = "password";
String plainText = "plaintext message to be encrypted";
// byte[] salt = generateSalt();
byte[] salt = "dfghjklpoiuytgftgyhj".getBytes();
Log.i(TAG, "Salt: " + salt.length + " " + HexEncoder.toHex(salt));
PBEKeySpec pbeKeySpec = new PBEKeySpec(password.toCharArray(), salt, PBE_ITERATION_COUNT);
SecretKeyFactory keyFac = SecretKeyFactory.getInstance(PBE_ALGORITHM);
SecretKey secretKey = keyFac.generateSecret(pbeKeySpec);
byte[] key = secretKey.getEncoded();
Log.i(TAG, "Key: " + HexEncoder.toHex(key));
// PBEParameterSpec pbeParamSpec = new PBEParameterSpec(salt, ITERATION_COUNT);
Cipher encryptionCipher = Cipher.getInstance(CIPHER_ALGORITHM);
// byte[] encryptionSalt = generateSalt();
// Log.i(TAG, "Encrypted Salt: " + encryptionSalt.length + " " + HexEncoder.toHex(encryptionSalt));
// PBEParameterSpec pbeParamSpec = new PBEParameterSpec(encryptionSalt, 1000);
// byte[] iv = params.getParameterSpec(IvParameterSpec.class).getIV();
// Log.i(TAG, encryptionCipher.getParameters() + " ");
byte[] iv = generateIv();
IvParameterSpec ivspec = new IvParameterSpec(iv);
encryptionCipher.init(Cipher.ENCRYPT_MODE, secretKey, ivspec);
byte[] encryptedText = encryptionCipher.doFinal(plainText.getBytes());
Log.i(TAG, "Encrypted: " + HexEncoder.toHex(encryptedText)); // <== Why is this always the same :(
Cipher decryptionCipher = Cipher.getInstance(CIPHER_ALGORITHM);
decryptionCipher.init(Cipher.DECRYPT_MODE, secretKey, ivspec);
byte[] decryptedText = decryptionCipher.doFinal(encryptedText);
Log.i(TAG, "Decrypted: " + new String(decryptedText));
} catch (Exception e) {
e.printStackTrace();
}
}
private byte[] generateSalt() throws NoSuchAlgorithmException {
SecureRandom random = SecureRandom.getInstance(RANDOM_ALGORITHM);
byte[] salt = new byte[SALT_LENGTH];
random.nextBytes(salt);
return salt;
}
private byte[] generateIv() throws NoSuchAlgorithmException {
SecureRandom random = SecureRandom.getInstance(RANDOM_ALGORITHM);
byte[] iv = new byte[16];
random.nextBytes(iv);
return iv;
}
}
