The project concerns the open-source libraries ‘Bouncy Castle’ and ‘PGPainless’, which provide cryptographic functions for ‘OpenPGP’. ‘OpenPGP’ is an open standard for the encryption and digital signing of data and messages. As part of a several milestones, new possibilities and concepts for the integration of smartcards and hardware security tokens are to be investigated on the basis of systematic analyses of existing functions, software architectures and specifications. The aim is to develop an interface that enables the secure use of hardware-based cryptographic keys in both libraries, thereby making a lasting contribution to strengthening the security and trustworthiness of open digital infrastructures in the public interest.