This application note describes FPGAs (field-programmable gate arrays) and how they can hold the key functions and the intellectual property (IP) of a system. It discusses ways to protect IP against piracy. SHA-1 challenge-and-response authentication is judged as the most secure methodology. This document presents a cost-effective authentication scheme that protects IP in SRAM-based FPGA designs. The DS28E01 and DS28CN01 1-Wire devices are featured.