Abstract: This document shows how Dallas Semiconductor/Maxim's SHA iButtons® and 1-Wire® devices can be used with small microcontrollers to provide strong encryption and authentication of control and status messages, telemetry, or sensitive process control information. For low cost and low overhead, it provides nonvolatile memory, secure secret storage, secret sharing and rotation, fast SHA-1 pad generation, and a globally unique serial number. A simple microcontroller needs only provide a single port pin and a few dozen lines of code to attain quality cryptographic security.