Riprap is a PREMIS-compliant fixity checking microservice. It was developed as a successor to Islandora 7.x's Checksum Checker module. It is intended primarily to be used with repositories compliant with the Fedora API Specification, but can be used to provide fixity validation for other repositories as well (e.g., an OCFL filesystem). To demonstrate its flexibility, Riprap ships with a ready-to-run sample configuration that allows it to monitor the fixity of files under a directory tree and call sha1sum to get their current digests.
Riprap periodically requests fixity digests for resources from a repository and compares the digest with a previously request digest. It then persists the outcome of that comparison so the process can be repeated again. Riprap also provides a REST interface so that external applications can retrieve fixity checking event data for use in reports, etc.