Specify Cipher.getInstance() arguments?

Question

I'm using the following in an android app and a standalone java app:

private static byte[] encrypt(byte[] raw, byte[] clear) throws Exception {
    SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");
    Cipher cipher = Cipher.getInstance("AES");
    cipher.init(Cipher.ENCRYPT_MODE, skeySpec);
    byte[] encrypted = cipher.doFinal(clear);
    ...

I get different encrypted strings on android vs my standalone java app (both using the same code and key). I get the same exception (javax.crypto.BadPaddingException: Blocktype mismatch: 0) as in this question:

RSA Encryption: Difference between Java and Android

And the suggested solution is to specify the padding strategy like:

Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");

but I'm using "AES", not "RSA", and am not sure how to specify the padding in combination with AES. How would I construct the string passed to Cipher.getInstance() in that case? I gave this a try:

Cipher cipher = Cipher.getInstance("AES/PKCS1Padding");

but get an exception about that being invalid.

Thanks

Solution 1

Another 'short answer', but I believe AES-GCM is more secure that CBC mode and been around for a couple of years however if you want to use in Android you'll need to include spongycastle

Cipher cipher = Cipher.getInstance("AES/GCM/NoPadding");

Solution 2

Short answer:

Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");

Long Answer

Solution 3

This is how I did it:

keyGenerator.init(new
                KeyGenParameterSpec.Builder(KEY_NAME,
                KeyProperties.PURPOSE_ENCRYPT |
                        KeyProperties.PURPOSE_DECRYPT)
                .setBlockModes(KeyProperties.BLOCK_MODE_CBC)
                .setUserAuthenticationRequired(true)
                .setEncryptionPaddings(
                        KeyProperties.ENCRYPTION_PADDING_PKCS7)
                .build());

cipher = Cipher.getInstance(KeyProperties.KEY_ALGORITHM_AES + "/" + KeyProperties.BLOCK_MODE_CBC + "/" + KeyProperties.ENCRYPTION_PADDING_PKCS7);

Comments

[user1811107]

In my case, I was calling a cipher.update when it should have been cipher.doFinal.

[alphaguy]

java.security.NoSuchAlgorithmException: AES/GCM/NoPadding SecretKeyFactory not available I am getting this error