Abstract: An authentication protocol (AP) of authenticating the connection and the exclusive and mutual cooperation of a specific software (SW) stored in and executed by a personal computer (PC) or a network personal computer (NPC) interconnected with a sewing machine (SM) and utilizing a standardized communication link (CL). Actualization of this is achieved, by evaluating and validating special data signatures generated, transmitted or received by each of personal computer (PC) and sewing machine (SM). The fixed sequence of transmitting and receiving said data signatures is comprised of the following steps: personal computer (PC) initializes authentication by issuing and sending authentication initialize signature (AI) to sewing machine (SM); if sewing machine (SM) is in an appropriate state, it issues and sends to personal computer (PC), an authentication acknowledge data signature (ACK).