CryptoAC (Cryptographic Access Control) provides end-to-end protection of sensitive data--such as documents, files and messages--through cryptographic enforcement of access control policies.
CryptoAC is an open-source tool written in the (multiplatform) Kotlin language; it comes either with an easy microservice-based architecture including an optimisation step to maximise the performance and the security of the deployment or, potentially, even as a programming library or plugin. CryptoAC is highly modular, can be easily extended to fit the needs of new scenarios and its APIs allow for straightforward integration with other services.
To get started right away, head over to the documentation.