swIDch PLC OTAC is an authentication solution for operational technology devices including programmable logic controllers (PLCs), remote terminal units (RTUs), SCADA systems, and human-machine interfaces (HMIs). The product replaces static password-based authentication with dynamic one-time authentication codes (OTAC) that generate unique codes for each access attempt. The solution addresses password-related vulnerabilities in OT environments such as password sharing, repeated password exposure, and compromised credentials. It maintains compatibility with existing 8-digit password setups while eliminating the need for manual password management, password changes, and password sharing between users. PLC OTAC provides compliance support for regulatory frameworks including IEC 62443, NIS2, and CRA through its authentication mechanism. The system offers audit trail capabilities and access control management per user and device. It supports tiered access management by device using dynamic codes. The product is available in multiple deployment models based on OT network levels: Server Model for Level 3-4 operations, Hybrid Model combining server and module components for Level 2 supervisory networks, and Standalone Module for Level 1 control networks. Each model can be configured to work with existing infrastructure with minimal system changes.