The integrity of a stored SOP Instance file (unencrypted) may be verified by a Message Authentication Code (MAC, also known as a message digest, hash, or cryptographic checksum) computed across the file. This value may be recomputed whenever a file is accessed, and that value compared to a previously computed MAC to assure that no changes have occurred to the file.

Inventories support recording a MAC computed by the storage system (the writing application) for files in the repository that will be accessible through a non-DICOM protocol. The file reading application can independently perform the MAC computation to assure integrity of the file as read or transferred.