PLC OTAC by swIDch is a secure authentication solution for Programmable Logic Controller (PLC) devices. It utilizes dynamic 'one-time authentication code' (OTAC) technology to address Industrial Control Systems (ICS) and Operational Technology (OT) security challenges. PLC OTAC enhances security for manufacturers and operators by eliminating password vulnerabilities and simplifying authentication with minimal disruption and computing requirements. It ensures high security with minimal resource requirements and can be deployed in various modes to deliver passwordless Multi-Factor Authentication (MFA) without the network.