int i;
        int len;
        if ( buf.length < TOK_ID_SIZE + MECH_OID_LEN_SIZE ) {
            throw new IllegalArgumentException();
        }
        // TOK_ID
        for ( i = 0; i < TOK_ID.length; i++ ) {
            if ( TOK_ID[ i ] != buf[ i ] ) {
                throw new IllegalArgumentException();
            }
        }
        // MECH_OID_LEN
        len = 0xff00 & ( buf[ i++ ] << 8 );