n.a unique alphanumeric value that represents the bitstream of an individual computer file or set of filesMoore 2006, 147A checksum is generated by an algorithm that combines all of the bits in the record to provide a reduced representation. A checksum can be evaluated and compared with the value stored in the logical attributes. If the record becomes corrupted, for example by damage to a tape on which it was stored, the data grid can replace it with a copy that has been previously verified as correct.Thomas and Martin 2006, 43Equipped with USB sticks, laptop and blank CDs to capture the digital records, the archivist follows a transfer protocol which includes the completion of a transfer form, recording any provisos, such as access restrictions, as well as checksum information to ensure that the material accessed at the repository is identical to that accessioned at the politician’s office.Daines 2013, 101, fn. 32A checksum is a fixed-sized datum computed from an arbitrary block of digital data for the purpose of detecting accidental errors that may have been introduced during transmission or storage.Daines 2013, 122The conservation assessment for digital materials involves the virus and malware check described above as well as monitoring of the checksums created for the digital files. This is a fundamental requirement in ensuring the authenticity of digital documents, because it guards against inadvertent or deliberate changes to the files, thus making it much easier for users to judge authenticity. If the checksums change, that indicates that the digital file has changed. Checksum values should remain the same over time; if they do not, the file has been modified or corrupted in some way on the bit level (the 1s and 0s a computer uses to encode a file).NDSA 2022Checksum: An algorithmically-computed numeric value for a file or a set of files used to validate the state and content of the file for the purpose of detecting accidental errors that may have been introduced during its transmission or storage. The integrity of the data can be checked at any later time by recomputing the checksum and comparing it with the stored one. If the checksums match, the data was almost certainly not altered. See also “Fixity Check.”
The term checksum is often used interchangeably with other types of fixity tools such as cryptographic hash values generated by algorithms such as MD5, SHA-1, and SHA-256. Checksums or hashes are used in the context of digital preservation, such as during the process of transferring or storing files, in order to determine whether files have been altered. For example, an archivist can compare checksums or hashes generated before and after file transfer to determine whether the file has maintained the same value through the transfer process.