def hex_uid(uid_raw):
    """
    Convert key to Hex string
    :param uid_raw: Input UID
    :return: Hex string
    """
    uid_list = list(uid_raw)
    uid_hex_str = ""
    for uid_item in uid_list:
        uid_hex = format(uid_item, 'x')
        if len(uid_hex) == 1:
            uid_hex = "0" + uid_hex
        uid_hex_str += uid_hex
    return uid_hex_str