Fixity Checksum

Collection Migration » Quality Control » Fixity Checksum

Long-term audiovisual preservation demands that no unintentional changes to file data be introduced by digital storage systems.  File fixity checks can be periodically performed to detect any changes.  Early detection of corrupted file data improves the likelihood of recovering the uncorrupted data.  It also minimizes the potential for corrupted data to propagate to file backups.

File fixity checks are performed by comparing a stored checksum value, made when a file was originally stored, to a checksum made from the file at a later time.  Checksums, or hash values, are numeric values calculated from the contents of a file using special algorithms.  Any change, large or small, in a file’s contents will result in a change of the calculated checksum.  Thus by comparing checksums calculated from the same file at two different times, changes in the file’s contents can be detected.

Checksums calculated by Video Transfer, can be used to determine if files delivered via any delivery method, have reached their destination without change.  They can also be used by storage systems that employ automatic monitoring systems to detect unwanted changes.