Cryptographic hash

A cryptographic hash produces a fixed-size digest from input data. For archival work, it can help check whether a file matches a previously recorded copy. NIST documents standardized families of hash functions; use an appropriate modern algorithm supported by your tools and record which algorithm produced the value. A matching digest is evidence about byte identity, not about the truth, authorship, or completeness of the content. An inaccurate document can be copied perfectly. Likewise, a legitimate format conversion changes the bytes and therefore normally changes the digest. Store hashes with filenames, dates, and source information, and keep the inventory independently of the only copy you are checking. When a value differs, investigate the cause rather than automatically assuming malicious alteration; ordinary editing or metadata changes can also explain it.

Editorial review: 2026-09-23. New evidence may change this account.

Report a problem with this record