A checksum on a file is a ‘digital fingerprint’ whereby even the smallest change to the file will cause the checksum to change completely. Checksums are typically created using cryptographic techniques and can be generated using a range of readily available and open source tools. It is important to note that whilst checksums can be used to detect if the contents of a file have changed, they do not tell you where in the file that the change has occurred.

Checksums have three main uses:

    1. To know that a file has been correctly received from a content owner or source and then transferred successfully to preservation storage
    2. To know that file fixity has been maintained when that file is being stored.
    3. To be given to users of the file in the future so they know that the file has been correctly retrieved from storage and delivered to them.

This allows a ‘chain of custody’ to be established between those who produce or supply the digital materials, those responsible for its ongoing storage, and those who need to use the digital material that has been stored. In the OAIS reference model (ISO, 2012) these are the producers, the OAIS itself is the repository, and the consumers. https://www.dpconline.org/handbook/technical-solutions-and-tools/fixity-and-checksums




Last modified: Thursday, 28 January 2021, 1:56 PM