The Fixity service will verify the bit-level integrity of files managed by the Storage service. File integrity is evaluated by first calculating a message digest for the file. These can take many forms, such as MD5, CRC-32, or SHA-1. This calculated message digest is then compared with one supplied or created at the time of ingest into a curation environment. If the file has been somehow corrupted, these two message digests will not match, which will signal the repository manager to interveneIn our development process for the Merritt repository, we first create a detailed specification for each micro-service and then develop software based upon the specification. Having a specification helps us think through issues and work out problems before we start to write code. It's always helpful to have people reviewing our specifications, to notice issues or implications we may have missed or not fully understood.