HSM stands for Hardware Security Module, which is a tamper-resistant physical device used to securely generate, store, and manage cryptographic keys and perform cryptographic operations. Payment industries commonly use specialized HSMs to protect keys and data for payment card personalization, transaction authorization, and verification. While HSMs provide high security, they are also expensive, so some companies offer HSM services running software that simulates an HSM's functions. The Thales Simulator is an open source software library that emulates the cryptographic functions of Thales HSM devices. It can be downloaded, installed, and configured to connect to over a network port to test applications designed to integrate with real HSM devices.