byte[] javaChecksum;
        if ( keybytes.length == 16 ) {
            javaChecksum = sun.security.krb5.internal.crypto.Aes128.calculateChecksum(keybytes, usage, bytes, 0, bytes.length);

        }
        else {
            javaChecksum = sun.security.krb5.internal.crypto.Aes256.calculateChecksum(keybytes, usage, bytes, 0, bytes.length);
        }