byte[] derivedKey = PacMac.deriveKeyAES(key, constant);
        assertNotNull(derivedKey);
        assertEquals(16, derivedKey.length);

        // Test with a different key size
        KerberosKey key256 = new KerberosKey(TEST_PRINCIPAL, new byte[32], PacSignature.ETYPE_AES256_CTS_HMAC_SHA1_96, 0);
        byte[] derivedKey256 = PacMac.deriveKeyAES(key256, constant);
        assertNotNull(derivedKey256);

        byte[] cst = { (byte) (usage >> 24 & 0xFF), (byte) (usage >> 16 & 0xFF), (byte) (usage >> 8 & 0xFF), (byte) (usage & 0xFF),
                (byte) 0x99 };

        byte[] output = new byte[12];
        byte[] dk = deriveKeyAES(baseKey, cst); // Checksum key
        try {
            Mac m = Mac.getInstance("HmacSHA1");
            m.init(new SecretKeySpec(dk, HMAC_KEY));
            System.arraycopy(m.doFinal(input), 0, output, 0, 12);