Android javax.crypto.BadPaddingException

Question

I am implementing encryption/decryption to my files. code is given below. I can't find out the problem. Am I missing anything? I need to implement 128 bit AES Encryption. Is there anything wrong? It end up with error

 "javax.crypto.BadPaddingException: error:1e06b065:Cipher functions:EVP_DecryptFinal_ex:BAD_DECRYPT"

Please help me.

private static byte[] encodeFile(byte[] yourKey, byte[] fileData)
        throws Exception {
    byte[] encrypted = null;
    SecretKeySpec skeySpec = new SecretKeySpec(yourKey, 0, yourKey.length, "AES");
    Cipher cipher = Cipher.getInstance("AES/ECB/PKCS7PADDING");
    cipher.init(Cipher.ENCRYPT_MODE, skeySpec);
    encrypted = cipher.doFinal(fileData);
    return encrypted;
}

private static byte[] generateKey() throws NoSuchAlgorithmException {
    byte[] keyStart = "This is my key".getBytes();
    String id = "dummypass";
    int iterationCount = 1000;
    int saltLength = 32;
    int keyLength = 128;
    SecureRandom random = new SecureRandom();
    byte[] salt = Arrays.copyOf(keyStart,saltLength);
    random.nextBytes(salt);
    KeySpec keySpec = new PBEKeySpec(id.toCharArray(), salt,
            iterationCount, keyLength);
    SecretKeyFactory keyFactory = SecretKeyFactory
            .getInstance("PBKDF2WithHmacSHA1");
    byte[] keyBytes = new byte[0];
    try {
        keyBytes = keyFactory.generateSecret(keySpec).getEncoded();
    } catch (InvalidKeySpecException e) {
        e.printStackTrace();
    }
    SecretKey key = new SecretKeySpec(keyBytes, "AES");
    return key.getEncoded();
}

private static byte[] decodeFile(byte[] yourKey, byte[] encryptedData)
        throws Exception {
    SecretKeySpec skeySpec = new SecretKeySpec(yourKey, 0, yourKey.length,
            "AES");
    Cipher cipher = Cipher.getInstance("AES/ECB/PKCS7PADDING");
    cipher.init(Cipher.DECRYPT_MODE, skeySpec);
    byte[] decrypted = cipher.doFinal(encryptedData);
    return decrypted;
}

public static void Encrypt(byte[] bytesToEncrypt, File target) {
    try {
        BufferedOutputStream bos = new BufferedOutputStream(
                new FileOutputStream(target));
        byte[] key = generateKey();
        byte[] encryptedBytes = encodeFile(key, bytesToEncrypt);
        bos.write(encryptedBytes);
        bos.flush();
        bos.close();
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    } catch (Exception e) {
        e.printStackTrace();
    }
}
public static  byte[] DecryptFile(byte[] bytesToDecrypt) {
    byte[] decodedData = new byte[0];
    try {
        byte[] key = generateKey();
        decodedData = decodeFile(key, bytesToDecrypt);
    } catch (Exception e) {
        e.printStackTrace();
    }
    return decodedData;
}

Answer 1

Verify that key is the same in both Encrypt and DecryptFile.

Since both call generateKey and generateKey calls SecureRandom nextBytes the keys are going to be different.

You need to save the encryption key for use during decryption.