Fixity is a verifiable quality of information. Data and information about the quality of fixity is used to ensure that there has been no undocumented alteration of digital or other information.
The attributes of fixity differ for various record media. For example, fixity in a hard copy or paper record may include considerations of the claimed date of creation as compared to the chemical composition of the media. Similarly, the physical impression of a signature is verifiable against other signature impressions to confirm authenticity.
In electronic records, fixity includes the integrity of hash algorithms and digital signatures used to "fix" the item in question within a context in an immutable way. When set within a process governed by fixity, then routine and ad hoc changes are tracked and attributable to specific actors (employees, customers, hackers).
Fixity is a critical factor in forensic analysis of authenticity.