SoftHSM

SoftHSM is an open-source software-based cryptographic module that emulates a hardware security module (HSM) by providing a PKCS#11 (Cryptoki) interface. It is designed to let developers and testers work with PKCS#11-enabled applications without requiring physical HSM hardware. SoftHSM implements a compliant PKCS#11 library and stores cryptographic objects on disk in a token-backed data store managed by the software.

SoftHSM is commonly used in development and continuous integration workflows to test key generation, signing, encryption, and token management workflows. Applications load SoftHSM as a PKCS#11 module and interact with named tokens through user credentials. The library is platform-agnostic in spirit and can be linked or loaded by applications across different operating systems.

The project includes a PKCS#11 library and a management utility for token administration. In SoftHSM 2.x, the management tool is used to initialize tokens, configure token labels, and manage keys and other objects. Tokens are organized into slots, and each token can hold multiple objects such as private keys, public keys, certificates, and symmetric keys, accessible after authentication.

SoftHSM is part of the OpenSC project and is available on multiple platforms, including Linux, Windows, and macOS. It is widely used for testing PKCS#11 integration and for development scenarios where hardware HSMs are impractical or unavailable.