Peter Peter - 1 month ago 23
Android Question

AES encryption: InvalidKeyException: Key length not 128/192/256 bits

I'm trying to encrypt a string on Android with AES. The symmetric key is determined previously with the Diffie-Hellman algorithm and seems to be ok (Key Length is 128 Bit, see below).

Nevertheless, I get a

InvalidKeyException: "Key length not 128/192/256 bits.
"

Code:

KeyAgreement keyAgree = KeyAgreement.getInstance("DH", "BC");
keyAgree.init(this.smartphonePrivKey);
keyAgree.doPhase(serverPubKey, true);
SecretKey key = keyAgree.generateSecret("AES");
System.out.println("Key Length: " + key.getEncoded().length);
System.out.println("Key Algorithm: "+ key.getAlgorithm());
System.out.println("Key Format: "+ key.getFormat());

byte[] encrypted = null;
Cipher cipher;
try {
cipher = Cipher.getInstance("AES/ECB/PKCS5Padding");
System.out.println("Allowed Key Length: "
+ cipher.getMaxAllowedKeyLength("AES"));
cipher.init(Cipher.ENCRYPT_MODE, key);
encrypted = cipher.doFinal("YEAH".getBytes("UTF8"));
} catch (NoSuchAlgorithmException e) {
e.printStackTrace();
} catch (NoSuchPaddingException e) {
e.printStackTrace();
} catch (InvalidKeyException e) {
e.printStackTrace();
} catch (IllegalBlockSizeException e) {
e.printStackTrace();
} catch (BadPaddingException e) {
e.printStackTrace();
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
}


The above Code leads to the following output:

_12-10 20:24:53.119: INFO/System.out(757): Key Length: 128_
_12-10 20:24:53.119: INFO/System.out(757): Key Algorithm: AES_
_12-10 20:24:53.119: INFO/System.out(757): Key Format: RAW_
_12-10 20:24:53.470: INFO/System.out(757): Allowed Key Length: 2147483647_


After that, I get the
InvalidKeyException: Key length not 128/192/256 bits.
But as you can see, the SecretKey has a length of 128 Bits!

Any ideas?

Thanks

Answer

The key you generated is 128 bytes, not 128 bits. "Key Length" should be 16.