File fixity is a

digital preservation In library and archival science, digital preservation is a formal endeavor to ensure that digital information of continuing value remains accessible and usable. It involves planning, resource allocation, and application of preservation methods an ...

term referring to the property of a digital file being fixed, or unchanged. Fixity checking is the process of verifying that a digital object has not been altered or corrupted. During transfer, a repository may run a fixity check to ensure a transmitted file has not been altered en route. Within the repository, fixity checking is used to ensure that digital files have not been affected by

data rot Bit rot may refer to: * " Bit Rot", a short story by Charles Stross * Data rot, the decay of electromagnetic charge in a computer's storage ** Disc rot Disc rot is the tendency of CD, DVD, or other optical discs to become unreadable because of ...

or other digital preservation dangers. By itself, fixity checking does not ensure the preservation of a digital file. Instead, it allows a repository to identify which corrupted files to replace with a clean copy from the producer or from a backup. In practice, a fixity check is most often accomplished by computing

checksum A checksum is a small-sized block of data derived from another block of digital data for the purpose of detecting errors that may have been introduced during its transmission or storage. By themselves, checksums are often used to verify data ...

cryptographic hash function A cryptographic hash function (CHF) is a hash algorithm (a map of an arbitrary binary string to a binary string with fixed size of n bits) that has special properties desirable for cryptography: * the probability of a particular n-bit output re ...

values for a file and comparing them to a stored value or through

digital signatures A digital signature is a mathematical scheme for verifying the authenticity of digital messages or documents. A valid digital signature, where the prerequisites are satisfied, gives a recipient very high confidence that the message was created b ...

. File fixity figures prominently in Preservation Metadata: Implementation Strategies (PREMIS), the

Government Printing Office The United States Government Publishing Office (USGPO or GPO; formerly the United States Government Printing Office) is an agency of the legislative branch of the United States Federal government. The office produces and distributes information ...

's work on the Authenticity of Electronic Federal Government Publications, and fixity checking practices are used by a range of cultural heritage organizations.

References

{{reflist Digital technology